StackGenVis/frontend/node_modules/vega/build/vega-module.js

import { dsvFormat } from 'd3-dsv';
import { feature, mesh } from 'topojson-client';
import { utcParse as utcParse$1, timeParse as timeParse$1, utcFormat as utcFormat$2, timeFormat as timeFormat$2 } from 'd3-time-format';
export { timeFormatDefaultLocale as timeFormatLocale } from 'd3-time-format';
import { utcWeek, timeWeek, timeYear, timeMonth, timeDay, timeHour, timeMinute, timeSecond, timeMillisecond, utcYear, utcMonth, utcDay, utcHour, utcMinute, utcSecond, utcMillisecond } from 'd3-time';
import { curveBasis, curveBasisClosed, curveBasisOpen, curveBundle, curveCardinal, curveCardinalOpen, curveCardinalClosed, curveCatmullRom, curveCatmullRomClosed, curveCatmullRomOpen, curveLinear, curveLinearClosed, curveMonotoneY, curveMonotoneX, curveNatural, curveStep, curveStepAfter, curveStepBefore, arc as arc$3, area as area$3, line as line$3, symbol as symbol$2 } from 'd3-shape';
import { path as path$3 } from 'd3-path';
import * as $$1 from 'd3-interpolate';
import { interpolateNumber, interpolateRound, interpolate as interpolate$1, piecewise } from 'd3-interpolate';
import { formatSpecifier, precisionFixed, precisionRound, precisionPrefix, formatPrefix, format as format$2 } from 'd3-format';
export { formatDefaultLocale as formatLocale } from 'd3-format';
import { geoProjection, geoPath, geoAlbers, geoAlbersUsa, geoAzimuthalEqualArea, geoAzimuthalEquidistant, geoConicConformal, geoConicEqualArea, geoConicEquidistant, geoEqualEarth, geoEquirectangular, geoGnomonic, geoIdentity, geoMercator, geoNaturalEarth1, geoOrthographic, geoStereographic, geoTransverseMercator, geoGraticule, geoBounds as geoBounds$1, geoCentroid as geoCentroid$1, geoArea as geoArea$1 } from 'd3-geo';
import { rgb, lab, hcl, hsl } from 'd3-color';
import { forceSimulation, forceCenter, forceCollide, forceManyBody, forceLink, forceX, forceY } from 'd3-force';
import { hierarchy, pack, partition as partition$5, stratify, tree as tree$1, cluster, treemap, treemapBinary, treemapDice, treemapSlice, treemapSliceDice, treemapSquarify, treemapResquarify } from 'd3-hierarchy';
import { interval } from 'd3-timer';

function accessor(fn, fields, name) {
  fn.fields = fields || [];
  fn.fname = name;
  return fn;
}

function accessorName(fn) {
  return fn == null ? null : fn.fname;
}

function accessorFields(fn) {
  return fn == null ? null : fn.fields;
}

function error(message) {
  throw Error(message);
}

function splitAccessPath(p) {
  var path = [],
      q = null,
      b = 0,
      n = p.length,
      s = '',
      i, j, c;

  p = p + '';

  function push() {
    path.push(s + p.substring(i, j));
    s = '';
    i = j + 1;
  }

  for (i=j=0; j<n; ++j) {
    c = p[j];
    if (c === '\\') {
      s += p.substring(i, j);
      s += p.substring(++j, ++j);
      i = j;
    } else if (c === q) {
      push();
      q = null;
      b = -1;
    } else if (q) {
      continue;
    } else if (i === b && c === '"') {
      i = j + 1;
      q = c;
    } else if (i === b && c === "'") {
      i = j + 1;
      q = c;
    } else if (c === '.' && !b) {
      if (j > i) {
        push();
      } else {
        i = j + 1;
      }
    } else if (c === '[') {
      if (j > i) push();
      b = i = j + 1;
    } else if (c === ']') {
      if (!b) error('Access path missing open bracket: ' + p);
      if (b > 0) push();
      b = 0;
      i = j + 1;
    }
  }

  if (b) error('Access path missing closing bracket: ' + p);
  if (q) error('Access path missing closing quote: ' + p);

  if (j > i) {
    j++;
    push();
  }

  return path;
}

var isArray = Array.isArray;

function isObject(_) {
  return _ === Object(_);
}

function isString(_) {
  return typeof _ === 'string';
}

function $(x) {
  return isArray(x) ? '[' + x.map($) + ']'
    : isObject(x) || isString(x) ?
      // Output valid JSON and JS source strings.
      // See http://timelessrepo.com/json-isnt-a-javascript-subset
      JSON.stringify(x).replace('\u2028','\\u2028').replace('\u2029', '\\u2029')
    : x;
}

function field(field, name) {
  var path = splitAccessPath(field),
      code = 'return _[' + path.map($).join('][') + '];';

  return accessor(
    Function('_', code),
    [(field = path.length===1 ? path[0] : field)],
    name || field
  );
}

var empty = [];

var id = field('id');

var identity = accessor(function(_) { return _; }, empty, 'identity');

var zero = accessor(function() { return 0; }, empty, 'zero');

var one = accessor(function() { return 1; }, empty, 'one');

var truthy = accessor(function() { return true; }, empty, 'true');

var falsy = accessor(function() { return false; }, empty, 'false');

function log(method, level, input) {
  var args = [level].concat([].slice.call(input));
  console[method].apply(console, args); // eslint-disable-line no-console
}

var None  = 0;
var Error$1 = 1;
var Warn  = 2;
var Info  = 3;
var Debug = 4;

function logger(_, method) {
  var level = _ || None;
  return {
    level: function(_) {
      if (arguments.length) {
        level = +_;
        return this;
      } else {
        return level;
      }
    },
    error: function() {
      if (level >= Error$1) log(method || 'error', 'ERROR', arguments);
      return this;
    },
    warn: function() {
      if (level >= Warn) log(method || 'warn', 'WARN', arguments);
      return this;
    },
    info: function() {
      if (level >= Info) log(method || 'log', 'INFO', arguments);
      return this;
    },
    debug: function() {
      if (level >= Debug) log(method || 'log', 'DEBUG', arguments);
      return this;
    }
  }
}

function mergeConfig(...configs) {
  return configs.reduce((out, source) => {
    for (var key in source) {
      if (key === 'signals') {
        // for signals, we merge the signals arrays
        // source signals take precedence over
        // existing signals with the same name
        out.signals = mergeNamed(out.signals, source.signals);
      } else {
        // otherwise, merge objects subject to recursion constraints
        // for legend block, recurse for the layout entry only
        // for style block, recurse for all properties
        // otherwise, no recursion: objects overwrite, no merging
        var r = key === 'legend' ? {'layout': 1}
          : key === 'style' ? true
          : null;
        writeConfig(out, key, source[key], r);
      }
    }
    return out;
  }, {});
}

function writeConfig(output, key, value, recurse) {
  var k, o;
  if (isObject(value) && !isArray(value)) {
    o = isObject(output[key]) ? output[key] : (output[key] = {});
    for (k in value) {
      if (recurse && (recurse === true || recurse[k])) {
        writeConfig(o, k, value[k]);
      } else {
        o[k] = value[k];
      }
    }
  } else {
    output[key] = value;
  }
}

function mergeNamed(a, b) {
  if (a == null) return b;

  const map = {}, out = [];

  function add(_) {
    if (!map[_.name]) {
      map[_.name] = 1;
      out.push(_);
    }
  }

  b.forEach(add);
  a.forEach(add);
  return out;
}

function peek(array) {
  return array[array.length - 1];
}

function toNumber(_) {
  return _ == null || _ === '' ? null : +_;
}

function exp(sign) {
  return function(x) { return sign * Math.exp(x); };
}

function log$1(sign) {
  return function(x) { return Math.log(sign * x); };
}

function symlog(c) {
  return function(x) { return Math.sign(x) * Math.log1p(Math.abs(x / c)); };
}

function symexp(c) {
  return function(x) { return Math.sign(x) * Math.expm1(Math.abs(x)) * c; };
}

function pow(exponent) {
  return function(x) {
    return x < 0 ? -Math.pow(-x, exponent) : Math.pow(x, exponent);
  };
}

function pan(domain, delta, lift, ground) {
  var d0 = lift(domain[0]),
      d1 = lift(peek(domain)),
      dd = (d1 - d0) * delta;

  return [
    ground(d0 - dd),
    ground(d1 - dd)
  ];
}

function panLinear(domain, delta) {
  return pan(domain, delta, toNumber, identity);
}

function panLog(domain, delta) {
  var sign = Math.sign(domain[0]);
  return pan(domain, delta, log$1(sign), exp(sign));
}

function panPow(domain, delta, exponent) {
  return pan(domain, delta, pow(exponent), pow(1/exponent));
}

function panSymlog(domain, delta, constant) {
  return pan(domain, delta, symlog(constant), symexp(constant));
}

function zoom(domain, anchor, scale, lift, ground) {
  var d0 = lift(domain[0]),
      d1 = lift(peek(domain)),
      da = anchor != null ? lift(anchor) : (d0 + d1) / 2;

  return [
    ground(da + (d0 - da) * scale),
    ground(da + (d1 - da) * scale)
  ];
}

function zoomLinear(domain, anchor, scale) {
  return zoom(domain, anchor, scale, toNumber, identity);
}

function zoomLog(domain, anchor, scale) {
  var sign = Math.sign(domain[0]);
  return zoom(domain, anchor, scale, log$1(sign), exp(sign));
}

function zoomPow(domain, anchor, scale, exponent) {
  return zoom(domain, anchor, scale, pow(exponent), pow(1/exponent));
}

function zoomSymlog(domain, anchor, scale, constant) {
  return zoom(domain, anchor, scale, symlog(constant), symexp(constant));
}

function quarter(date) {
  return 1 + ~~(new Date(date).getMonth() / 3);
}

function utcquarter(date) {
  return 1 + ~~(new Date(date).getUTCMonth() / 3);
}

function array(_) {
  return _ != null ? (isArray(_) ? _ : [_]) : [];
}

/**
 * Span-preserving range clamp. If the span of the input range is less
 * than (max - min) and an endpoint exceeds either the min or max value,
 * the range is translated such that the span is preserved and one
 * endpoint touches the boundary of the min/max range.
 * If the span exceeds (max - min), the range [min, max] is returned.
 */
function clampRange(range, min, max) {
  var lo = range[0],
      hi = range[1],
      span;

  if (hi < lo) {
    span = hi;
    hi = lo;
    lo = span;
  }
  span = hi - lo;

  return span >= (max - min)
    ? [min, max]
    : [
        (lo = Math.min(Math.max(lo, min), max - span)),
        lo + span
      ];
}

function isFunction(_) {
  return typeof _ === 'function';
}

function compare(fields, orders) {
  var idx = [],
      cmp = (fields = array(fields)).map(function(f, i) {
        if (f == null) {
          return null;
        } else {
          idx.push(i);
          return isFunction(f) ? f
            : splitAccessPath(f).map($).join('][');
        }
      }),
      n = idx.length - 1,
      ord = array(orders),
      code = 'var u,v;return ',
      i, j, f, u, v, d, t, lt, gt;

  if (n < 0) return null;

  for (j=0; j<=n; ++j) {
    i = idx[j];
    f = cmp[i];

    if (isFunction(f)) {
      d = 'f' + i;
      u = '(u=this.' + d + '(a))';
      v = '(v=this.' + d + '(b))';
      (t = t || {})[d] = f;
    } else {
      u = '(u=a['+f+'])';
      v = '(v=b['+f+'])';
    }

    d = '((v=v instanceof Date?+v:v),(u=u instanceof Date?+u:u))';

    if (ord[i] !== 'descending') {
      gt = 1;
      lt = -1;
    } else {
      gt = -1;
      lt = 1;
    }

    code += '(' + u+'<'+v+'||u==null)&&v!=null?' + lt
      + ':(u>v||v==null)&&u!=null?' + gt
      + ':'+d+'!==u&&v===v?' + lt
      + ':v!==v&&u===u?' + gt
      + (i < n ? ':' : ':0');
  }

  f = Function('a', 'b', code + ';');
  if (t) f = f.bind(t);

  fields = fields.reduce(function(map, field) {
    if (isFunction(field)) {
      (accessorFields(field) || []).forEach(function(_) { map[_] = 1; });
    } else if (field != null) {
      map[field + ''] = 1;
    }
    return map;
  }, {});

  return accessor(f, Object.keys(fields));
}

function constant(_) {
  return isFunction(_) ? _ : function() { return _; };
}

function debounce(delay, handler) {
  var tid, evt;

  function callback() {
    handler(evt);
    tid = evt = null;
  }

  return function(e) {
    evt = e;
    if (tid) clearTimeout(tid);
    tid = setTimeout(callback, delay);
  };
}

function extend(_) {
  for (var x, k, i=1, len=arguments.length; i<len; ++i) {
    x = arguments[i];
    for (k in x) { _[k] = x[k]; }
  }
  return _;
}

/**
 * Return an array with minimum and maximum values, in the
 * form [min, max]. Ignores null, undefined, and NaN values.
 */
function extent(array, f) {
  var i = 0, n, v, min, max;

  if (array && (n = array.length)) {
    if (f == null) {
      // find first valid value
      for (v = array[i]; i < n && (v == null || v !== v); v = array[++i]);
      min = max = v;

      // visit all other values
      for (; i<n; ++i) {
        v = array[i];
        // skip null/undefined; NaN will fail all comparisons
        if (v != null) {
          if (v < min) min = v;
          if (v > max) max = v;
        }
      }
    } else {
      // find first valid value
      for (v = f(array[i]); i < n && (v == null || v !== v); v = f(array[++i]));
      min = max = v;

      // visit all other values
      for (; i<n; ++i) {
        v = f(array[i]);
        // skip null/undefined; NaN will fail all comparisons
        if (v != null) {
          if (v < min) min = v;
          if (v > max) max = v;
        }
      }
    }
  }

  return [min, max];
}

function extentIndex(array, f) {
  var i = -1,
      n = array.length,
      a, b, c, u, v;

  if (f == null) {
    while (++i < n) {
      b = array[i];
      if (b != null && b >= b) {
        a = c = b;
        break;
      }
    }
    if (i === n) return [-1, -1];
    u = v = i;
    while (++i < n) {
      b = array[i];
      if (b != null) {
        if (a > b) {
          a = b;
          u = i;
        }
        if (c < b) {
          c = b;
          v = i;
        }
      }
    }
  } else {
    while (++i < n) {
      b = f(array[i], i, array);
      if (b != null && b >= b) {
        a = c = b;
        break;
      }
    }
    if (i === n) return [-1, -1];
    u = v = i;
    while (++i < n) {
      b = f(array[i], i, array);
      if (b != null) {
        if (a > b) {
          a = b;
          u = i;
        }
        if (c < b) {
          c = b;
          v = i;
        }
      }
    }
  }

  return [u, v];
}

const hop = Object.prototype.hasOwnProperty;

function hasOwnProperty(object, property) {
  return hop.call(object, property);
}

var NULL = {};

function fastmap(input) {
  var obj = {},
      map,
      test;

  function has(key) {
    return hasOwnProperty(obj, key) && obj[key] !== NULL;
  }

  map = {
    size: 0,
    empty: 0,
    object: obj,
    has: has,
    get: function(key) {
      return has(key) ? obj[key] : undefined;
    },
    set: function(key, value) {
      if (!has(key)) {
        ++map.size;
        if (obj[key] === NULL) --map.empty;
      }
      obj[key] = value;
      return this;
    },
    delete: function(key) {
      if (has(key)) {
        --map.size;
        ++map.empty;
        obj[key] = NULL;
      }
      return this;
    },
    clear: function() {
      map.size = map.empty = 0;
      map.object = obj = {};
    },
    test: function(_) {
      if (arguments.length) {
        test = _;
        return map;
      } else {
        return test;
      }
    },
    clean: function() {
      var next = {},
          size = 0,
          key, value;
      for (key in obj) {
        value = obj[key];
        if (value !== NULL && (!test || !test(value))) {
          next[key] = value;
          ++size;
        }
      }
      map.size = size;
      map.empty = 0;
      map.object = (obj = next);
    }
  };

  if (input) Object.keys(input).forEach(function(key) {
    map.set(key, input[key]);
  });

  return map;
}

function flush(range, value, threshold, left, right, center) {
  if (!threshold && threshold !== 0) return center;

  var a = range[0],
      b = peek(range),
      t = +threshold,
      l, r;

  // swap endpoints if range is reversed
  if (b < a) {
    l = a; a = b; b = l;
  }

  // compare value to endpoints
  l = Math.abs(value - a);
  r = Math.abs(b - value);

  // adjust if value is within threshold distance of endpoint
  return l < r && l <= t ? left : r <= t ? right : center;
}

function inherits(child, parent) {
  var proto = (child.prototype = Object.create(parent.prototype));
  proto.constructor = child;
  return proto;
}

/**
 * Predicate that returns true if the value lies within the span
 * of the given range. The left and right flags control the use
 * of inclusive (true) or exclusive (false) comparisons.
 */
function inrange(value, range, left, right) {
  var r0 = range[0], r1 = range[range.length-1], t;
  if (r0 > r1) {
    t = r0;
    r0 = r1;
    r1 = t;
  }
  left = left === undefined || left;
  right = right === undefined || right;

  return (left ? r0 <= value : r0 < value) &&
    (right ? value <= r1 : value < r1);
}

function isBoolean(_) {
  return typeof _ === 'boolean';
}

function isDate(_) {
  return Object.prototype.toString.call(_) === '[object Date]';
}

function isNumber(_) {
  return typeof _ === 'number';
}

function isRegExp(_) {
  return Object.prototype.toString.call(_) === '[object RegExp]';
}

function key(fields, flat) {
  if (fields) {
    fields = flat
      ? array(fields).map(function(f) { return f.replace(/\\(.)/g, '$1'); })
      : array(fields);
  }

  var fn = !(fields && fields.length)
    ? function() { return ''; }
    : Function('_', 'return \'\'+' +
        fields.map(function(f) {
          return '_[' + (flat
              ? $(f)
              : splitAccessPath(f).map($).join('][')
            ) + ']';
        }).join('+\'|\'+') + ';');

  return accessor(fn, fields, 'key');
}

function lerp(array, frac) {
  const lo = array[0],
        hi = peek(array),
        f = +frac;
  return !f ? lo : f === 1 ? hi : lo + f * (hi - lo);
}

function merge(compare, array0, array1, output) {
  var n0 = array0.length,
      n1 = array1.length;

  if (!n1) return array0;
  if (!n0) return array1;

  var merged = output || new array0.constructor(n0 + n1),
      i0 = 0, i1 = 0, i = 0;

  for (; i0<n0 && i1<n1; ++i) {
    merged[i] = compare(array0[i0], array1[i1]) > 0
       ? array1[i1++]
       : array0[i0++];
  }

  for (; i0<n0; ++i0, ++i) {
    merged[i] = array0[i0];
  }

  for (; i1<n1; ++i1, ++i) {
    merged[i] = array1[i1];
  }

  return merged;
}

function repeat(str, reps) {
  var s = '';
  while (--reps >= 0) s += str;
  return s;
}

function pad(str, length, padchar, align) {
  var c = padchar || ' ',
      s = str + '',
      n = length - s.length;

  return n <= 0 ? s
    : align === 'left' ? repeat(c, n) + s
    : align === 'center' ? repeat(c, ~~(n/2)) + s + repeat(c, Math.ceil(n/2))
    : s + repeat(c, n);
}

/**
 * Return the numerical span of an array: the difference between
 * the last and first values.
 */
function span(array) {
  return array && (peek(array) - array[0]) || 0;
}

function toBoolean(_) {
  return _ == null || _ === '' ? null : !_ || _ === 'false' || _ === '0' ? false : !!_;
}

function defaultParser(_) {
  return isNumber(_) ? _ : isDate(_) ? _ : Date.parse(_);
}

function toDate(_, parser) {
  parser = parser || defaultParser;
  return _ == null || _ === '' ? null : parser(_);
}

function toString(_) {
  return _ == null || _ === '' ? null : _ + '';
}

function toSet(_) {
  for (var s={}, i=0, n=_.length; i<n; ++i) s[_[i]] = true;
  return s;
}

function truncate(str, length, align, ellipsis) {
  var e = ellipsis != null ? ellipsis : '\u2026',
      s = str + '',
      n = s.length,
      l = Math.max(0, length - e.length);

  return n <= length ? s
    : align === 'left' ? e + s.slice(n - l)
    : align === 'center' ? s.slice(0, Math.ceil(l/2)) + e + s.slice(n - ~~(l/2))
    : s.slice(0, l) + e;
}

function visitArray(array, filter, visitor) {
  if (array) {
    var i = 0, n = array.length, t;
    if (filter) {
      for (; i<n; ++i) {
        if (t = filter(array[i])) visitor(t, i, array);
      }
    } else {
      array.forEach(visitor);
    }
  }
}

function UniqueList(idFunc) {
  var $ = idFunc || identity,
      list = [],
      ids = {};

  list.add = function(_) {
    var id = $(_);
    if (!ids[id]) {
      ids[id] = 1;
      list.push(_);
    }
    return list;
  };

  list.remove = function(_) {
    var id = $(_), idx;
    if (ids[id]) {
      ids[id] = 0;
      if ((idx = list.indexOf(_)) >= 0) {
        list.splice(idx, 1);
      }
    }
    return list;
  };

  return list;
}

/**
 * Invoke and await a potentially async callback function. If
 * an error occurs, trap it and route to Dataflow.error.
 * @param {Dataflow} df - The dataflow instance
 * @param {function} callback - A callback function to invoke
 *   and then await. The dataflow will be passed as the single
 *   argument to the function.
 */
async function asyncCallback(df, callback) {
  try { await callback(df); } catch (err) { df.error(err); }
}

var TUPLE_ID_KEY = Symbol('vega_id'),
    TUPLE_ID = 1;

/**
 * Checks if an input value is a registered tuple.
 * @param {*} t - The value to check.
 * @return {boolean} True if the input is a tuple, false otherwise.
 */
function isTuple(t) {
  return !!(t && tupleid(t));
}

/**
 * Returns the id of a tuple.
 * @param {object} t - The input tuple.
 * @return {*} the tuple id.
 */
function tupleid(t) {
  return t[TUPLE_ID_KEY];
}

/**
 * Sets the id of a tuple.
 * @param {object} t - The input tuple.
 * @param {*} id - The id value to set.
 * @return {object} the input tuple.
 */
function setid(t, id) {
  t[TUPLE_ID_KEY] = id;
  return t;
}

/**
 * Ingest an object or value as a data tuple.
 * If the input value is an object, an id field will be added to it. For
 * efficiency, the input object is modified directly. A copy is not made.
 * If the input value is a literal, it will be wrapped in a new object
 * instance, with the value accessible as the 'data' property.
 * @param datum - The value to ingest.
 * @return {object} The ingested data tuple.
 */
function ingest(datum) {
  var t = (datum === Object(datum)) ? datum : {data: datum};
  return tupleid(t) ? t : setid(t, TUPLE_ID++);
}

/**
 * Given a source tuple, return a derived copy.
 * @param {object} t - The source tuple.
 * @return {object} The derived tuple.
 */
function derive(t) {
  return rederive(t, ingest({}));
}

/**
 * Rederive a derived tuple by copying values from the source tuple.
 * @param {object} t - The source tuple.
 * @param {object} d - The derived tuple.
 * @return {object} The derived tuple.
 */
function rederive(t, d) {
  for (var k in t) d[k] = t[k];
  return d;
}

/**
 * Replace an existing tuple with a new tuple.
 * @param {object} t - The existing data tuple.
 * @param {object} d - The new tuple that replaces the old.
 * @return {object} The new tuple.
 */
function replace(t, d) {
  return setid(d, tupleid(t));
}

/**
 * Generate an augmented comparator function that provides stable
 * sorting by tuple id when the given comparator produces ties.
 * @param {function} cmp - The comparator to augment.
 * @param {function} [f] - Optional tuple accessor function.
 * @return {function} An augmented comparator function.
 */
function stableCompare(cmp, f) {
  return !cmp ? null
    : f ? (a, b) => cmp(a, b) || (tupleid(f(a)) - tupleid(f(b)))
    : (a, b) => cmp(a, b) || (tupleid(a) - tupleid(b));
}

function isChangeSet(v) {
  return v && v.constructor === changeset;
}

function changeset() {
  var add = [],  // insert tuples
      rem = [],  // remove tuples
      mod = [],  // modify tuples
      remp = [], // remove by predicate
      modp = [], // modify by predicate
      reflow = false;

  return {
    constructor: changeset,
    insert: function(t) {
      var d = array(t), i = 0, n = d.length;
      for (; i<n; ++i) add.push(d[i]);
      return this;
    },
    remove: function(t) {
      var a = isFunction(t) ? remp : rem,
          d = array(t), i = 0, n = d.length;
      for (; i<n; ++i) a.push(d[i]);
      return this;
    },
    modify: function(t, field, value) {
      var m = {field: field, value: constant(value)};
      if (isFunction(t)) {
        m.filter = t;
        modp.push(m);
      } else {
        m.tuple = t;
        mod.push(m);
      }
      return this;
    },
    encode: function(t, set) {
      if (isFunction(t)) modp.push({filter: t, field: set});
      else mod.push({tuple: t, field: set});
      return this;
    },
    reflow: function() {
      reflow = true;
      return this;
    },
    pulse: function(pulse, tuples) {
      var cur = {}, out = {}, i, n, m, f, t, id;

      // build lookup table of current tuples
      for (i=0, n=tuples.length; i<n; ++i) {
        cur[tupleid(tuples[i])] = 1;
      }

      // process individual tuples to remove
      for (i=0, n=rem.length; i<n; ++i) {
        t = rem[i];
        cur[tupleid(t)] = -1;
      }

      // process predicate-based removals
      for (i=0, n=remp.length; i<n; ++i) {
        f = remp[i];
        tuples.forEach(function(t) {
          if (f(t)) cur[tupleid(t)] = -1;
        });
      }

      // process all add tuples
      for (i=0, n=add.length; i<n; ++i) {
        t = add[i];
        id = tupleid(t);
        if (cur[id]) {
          // tuple already resides in dataset
          // if flagged for both add and remove, cancel
          cur[id] = 1;
        } else {
          // tuple does not reside in dataset, add
          pulse.add.push(ingest(add[i]));
        }
      }

      // populate pulse rem list
      for (i=0, n=tuples.length; i<n; ++i) {
        t = tuples[i];
        if (cur[tupleid(t)] < 0) pulse.rem.push(t);
      }

      // modify helper method
      function modify(t, f, v) {
        if (v) {
          t[f] = v(t);
        } else {
          pulse.encode = f;
        }
        if (!reflow) out[tupleid(t)] = t;
      }

      // process individual tuples to modify
      for (i=0, n=mod.length; i<n; ++i) {
        m = mod[i];
        t = m.tuple;
        f = m.field;
        id = cur[tupleid(t)];
        if (id > 0) {
          modify(t, f, m.value);
          pulse.modifies(f);
        }
      }

      // process predicate-based modifications
      for (i=0, n=modp.length; i<n; ++i) {
        m = modp[i];
        f = m.filter;
        tuples.forEach(function(t) {
          if (f(t) && cur[tupleid(t)] > 0) {
            modify(t, m.field, m.value);
          }
        });
        pulse.modifies(m.field);
      }

      // upon reflow request, populate mod with all non-removed tuples
      // otherwise, populate mod with modified tuples only
      if (reflow) {
        pulse.mod = rem.length || remp.length
          ? tuples.filter(function(t) { return cur[tupleid(t)] > 0; })
          : tuples.slice();
      } else {
        for (id in out) pulse.mod.push(out[id]);
      }

      return pulse;
    }
  };
}

var CACHE = '_:mod:_';

/**
 * Hash that tracks modifications to assigned values.
 * Callers *must* use the set method to update values.
 */
function Parameters() {
  Object.defineProperty(this, CACHE, {writable: true, value: {}});
}

var prototype = Parameters.prototype;

/**
 * Set a parameter value. If the parameter value changes, the parameter
 * will be recorded as modified.
 * @param {string} name - The parameter name.
 * @param {number} index - The index into an array-value parameter. Ignored if
 *   the argument is undefined, null or less than zero.
 * @param {*} value - The parameter value to set.
 * @param {boolean} [force=false] - If true, records the parameter as modified
 *   even if the value is unchanged.
 * @return {Parameters} - This parameter object.
 */
prototype.set = function(name, index, value, force) {
  var o = this,
      v = o[name],
      mod = o[CACHE];

  if (index != null && index >= 0) {
    if (v[index] !== value || force) {
      v[index] = value;
      mod[index + ':' + name] = -1;
      mod[name] = -1;
    }
  } else if (v !== value || force) {
    o[name] = value;
    mod[name] = isArray(value) ? 1 + value.length : -1;
  }

  return o;
};

/**
 * Tests if one or more parameters has been modified. If invoked with no
 * arguments, returns true if any parameter value has changed. If the first
 * argument is array, returns trues if any parameter name in the array has
 * changed. Otherwise, tests if the given name and optional array index has
 * changed.
 * @param {string} name - The parameter name to test.
 * @param {number} [index=undefined] - The parameter array index to test.
 * @return {boolean} - Returns true if a queried parameter was modified.
 */
prototype.modified = function(name, index) {
  var mod = this[CACHE], k;
  if (!arguments.length) {
    for (k in mod) { if (mod[k]) return true; }
    return false;
  } else if (isArray(name)) {
    for (k=0; k<name.length; ++k) {
      if (mod[name[k]]) return true;
    }
    return false;
  }
  return (index != null && index >= 0)
    ? (index + 1 < mod[name] || !!mod[index + ':' + name])
    : !!mod[name];
};

/**
 * Clears the modification records. After calling this method,
 * all parameters are considered unmodified.
 */
prototype.clear = function() {
  this[CACHE] = {};
  return this;
};

var OP_ID = 0;
var PULSE = 'pulse';
var NO_PARAMS = new Parameters();

// Boolean Flags
var SKIP     = 1,
    MODIFIED = 2;

/**
 * An Operator is a processing node in a dataflow graph.
 * Each operator stores a value and an optional value update function.
 * Operators can accept a hash of named parameters. Parameter values can
 * either be direct (JavaScript literals, arrays, objects) or indirect
 * (other operators whose values will be pulled dynamically). Operators
 * included as parameters will have this operator added as a dependency.
 * @constructor
 * @param {*} [init] - The initial value for this operator.
 * @param {function(object, Pulse)} [update] - An update function. Upon
 *   evaluation of this operator, the update function will be invoked and the
 *   return value will be used as the new value of this operator.
 * @param {object} [params] - The parameters for this operator.
 * @param {boolean} [react=true] - Flag indicating if this operator should
 *   listen for changes to upstream operators included as parameters.
 * @see parameters
 */
function Operator(init, update, params, react) {
  this.id = ++OP_ID;
  this.value = init;
  this.stamp = -1;
  this.rank = -1;
  this.qrank = -1;
  this.flags = 0;

  if (update) {
    this._update = update;
  }
  if (params) this.parameters(params, react);
}

var prototype$1 = Operator.prototype;

/**
 * Returns a list of target operators dependent on this operator.
 * If this list does not exist, it is created and then returned.
 * @return {UniqueList}
 */
prototype$1.targets = function() {
  return this._targets || (this._targets = UniqueList(id));
};

/**
 * Sets the value of this operator.
 * @param {*} value - the value to set.
 * @return {Number} Returns 1 if the operator value has changed
 *   according to strict equality, returns 0 otherwise.
 */
prototype$1.set = function(value) {
  if (this.value !== value) {
    this.value = value;
    return 1;
  } else {
    return 0;
  }
};

function flag(bit) {
  return function(state) {
    var f = this.flags;
    if (arguments.length === 0) return !!(f & bit);
    this.flags = state ? (f | bit) : (f & ~bit);
    return this;
  };
}

/**
 * Indicates that operator evaluation should be skipped on the next pulse.
 * This operator will still propagate incoming pulses, but its update function
 * will not be invoked. The skip flag is reset after every pulse, so calling
 * this method will affect processing of the next pulse only.
 */
prototype$1.skip = flag(SKIP);

/**
 * Indicates that this operator's value has been modified on its most recent
 * pulse. Normally modification is checked via strict equality; however, in
 * some cases it is more efficient to update the internal state of an object.
 * In those cases, the modified flag can be used to trigger propagation. Once
 * set, the modification flag persists across pulses until unset. The flag can
 * be used with the last timestamp to test if a modification is recent.
 */
prototype$1.modified = flag(MODIFIED);

/**
 * Sets the parameters for this operator. The parameter values are analyzed for
 * operator instances. If found, this operator will be added as a dependency
 * of the parameterizing operator. Operator values are dynamically marshalled
 * from each operator parameter prior to evaluation. If a parameter value is
 * an array, the array will also be searched for Operator instances. However,
 * the search does not recurse into sub-arrays or object properties.
 * @param {object} params - A hash of operator parameters.
 * @param {boolean} [react=true] - A flag indicating if this operator should
 *   automatically update (react) when parameter values change. In other words,
 *   this flag determines if the operator registers itself as a listener on
 *   any upstream operators included in the parameters.
 * @param {boolean} [initonly=false] - A flag indicating if this operator
 *   should calculate an update only upon its initiatal evaluation, then
 *   deregister dependencies and suppress all future update invocations.
 * @return {Operator[]} - An array of upstream dependencies.
 */
prototype$1.parameters = function(params, react, initonly) {
  react = react !== false;
  var self = this,
      argval = (self._argval = self._argval || new Parameters()),
      argops = (self._argops = self._argops || []),
      deps = [],
      name, value, n, i;

  function add(name, index, value) {
    if (value instanceof Operator) {
      if (value !== self) {
        if (react) value.targets().add(self);
        deps.push(value);
      }
      argops.push({op:value, name:name, index:index});
    } else {
      argval.set(name, index, value);
    }
  }

  for (name in params) {
    value = params[name];

    if (name === PULSE) {
      array(value).forEach(function(op) {
        if (!(op instanceof Operator)) {
          error('Pulse parameters must be operator instances.');
        } else if (op !== self) {
          op.targets().add(self);
          deps.push(op);
        }
      });
      self.source = value;
    } else if (isArray(value)) {
      argval.set(name, -1, Array(n = value.length));
      for (i=0; i<n; ++i) add(name, i, value[i]);
    } else {
      add(name, -1, value);
    }
  }

  this.marshall().clear(); // initialize values
  if (initonly) argops.initonly = true;

  return deps;
};

/**
 * Internal method for marshalling parameter values.
 * Visits each operator dependency to pull the latest value.
 * @return {Parameters} A Parameters object to pass to the update function.
 */
prototype$1.marshall = function(stamp) {
  var argval = this._argval || NO_PARAMS,
      argops = this._argops, item, i, n, op, mod;

  if (argops) {
    for (i=0, n=argops.length; i<n; ++i) {
      item = argops[i];
      op = item.op;
      mod = op.modified() && op.stamp === stamp;
      argval.set(item.name, item.index, op.value, mod);
    }

    if (argops.initonly) {
      for (i=0; i<n; ++i) {
        item = argops[i];
        item.op.targets().remove(this);
      }
      this._argops = null;
      this._update = null;
    }
  }
  return argval;
};

/**
 * Delegate method to perform operator processing.
 * Subclasses can override this method to perform custom processing.
 * By default, it marshalls parameters and calls the update function
 * if that function is defined. If the update function does not
 * change the operator value then StopPropagation is returned.
 * If no update function is defined, this method does nothing.
 * @param {Pulse} pulse - the current dataflow pulse.
 * @return The output pulse or StopPropagation. A falsy return value
 *   (including undefined) will let the input pulse pass through.
 */
prototype$1.evaluate = function(pulse) {
  var update = this._update;
  if (update) {
    var params = this.marshall(pulse.stamp),
        v = update.call(this, params, pulse);

    params.clear();
    if (v !== this.value) {
      this.value = v;
    } else if (!this.modified()) {
      return pulse.StopPropagation;
    }
  }
};

/**
 * Run this operator for the current pulse. If this operator has already
 * been run at (or after) the pulse timestamp, returns StopPropagation.
 * Internally, this method calls {@link evaluate} to perform processing.
 * If {@link evaluate} returns a falsy value, the input pulse is returned.
 * This method should NOT be overridden, instead overrride {@link evaluate}.
 * @param {Pulse} pulse - the current dataflow pulse.
 * @return the output pulse for this operator (or StopPropagation)
 */
prototype$1.run = function(pulse) {
  if (pulse.stamp < this.stamp) return pulse.StopPropagation;
  var rv;
  if (this.skip()) {
    this.skip(false);
    rv = 0;
  } else {
    rv = this.evaluate(pulse);
  }
  return (this.pulse = rv || pulse);
};

/**
 * Add an operator to the dataflow graph. This function accepts a
 * variety of input argument types. The basic signature supports an
 * initial value, update function and parameters. If the first parameter
 * is an Operator instance, it will be added directly. If it is a
 * constructor for an Operator subclass, a new instance will be instantiated.
 * Otherwise, if the first parameter is a function instance, it will be used
 * as the update function and a null initial value is assumed.
 * @param {*} init - One of: the operator to add, the initial value of
 *   the operator, an operator class to instantiate, or an update function.
 * @param {function} [update] - The operator update function.
 * @param {object} [params] - The operator parameters.
 * @param {boolean} [react=true] - Flag indicating if this operator should
 *   listen for changes to upstream operators included as parameters.
 * @return {Operator} - The added operator.
 */
function add(init, update, params, react) {
  var shift = 1,
    op;

  if (init instanceof Operator) {
    op = init;
  } else if (init && init.prototype instanceof Operator) {
    op = new init();
  } else if (isFunction(init)) {
    op = new Operator(null, init);
  } else {
    shift = 0;
    op = new Operator(init, update);
  }

  this.rank(op);
  if (shift) {
    react = params;
    params = update;
  }
  if (params) this.connect(op, op.parameters(params, react));
  this.touch(op);

  return op;
}

/**
 * Connect a target operator as a dependent of source operators.
 * If necessary, this method will rerank the target operator and its
 * dependents to ensure propagation proceeds in a topologically sorted order.
 * @param {Operator} target - The target operator.
 * @param {Array<Operator>} - The source operators that should propagate
 *   to the target operator.
 */
function connect(target, sources) {
  var targetRank = target.rank, i, n;

  for (i=0, n=sources.length; i<n; ++i) {
    if (targetRank < sources[i].rank) {
      this.rerank(target);
      return;
    }
  }
}

var STREAM_ID = 0;

/**
 * Models an event stream.
 * @constructor
 * @param {function(Object, number): boolean} [filter] - Filter predicate.
 *   Events pass through when truthy, events are suppressed when falsy.
 * @param {function(Object): *} [apply] - Applied to input events to produce
 *   new event values.
 * @param {function(Object)} [receive] - Event callback function to invoke
 *   upon receipt of a new event. Use to override standard event processing.
 */
function EventStream(filter, apply, receive) {
  this.id = ++STREAM_ID;
  this.value = null;
  if (receive) this.receive = receive;
  if (filter) this._filter = filter;
  if (apply) this._apply = apply;
}

/**
 * Creates a new event stream instance with the provided
 * (optional) filter, apply and receive functions.
 * @param {function(Object, number): boolean} [filter] - Filter predicate.
 *   Events pass through when truthy, events are suppressed when falsy.
 * @param {function(Object): *} [apply] - Applied to input events to produce
 *   new event values.
 * @see EventStream
 */
function stream(filter, apply, receive) {
  return new EventStream(filter, apply, receive);
}

var prototype$2 = EventStream.prototype;

prototype$2._filter = truthy;

prototype$2._apply = identity;

prototype$2.targets = function() {
  return this._targets || (this._targets = UniqueList(id));
};

prototype$2.consume = function(_) {
  if (!arguments.length) return !!this._consume;
  this._consume = !!_;
  return this;
};

prototype$2.receive = function(evt) {
  if (this._filter(evt)) {
    var val = (this.value = this._apply(evt)),
        trg = this._targets,
        n = trg ? trg.length : 0,
        i = 0;

    for (; i<n; ++i) trg[i].receive(val);

    if (this._consume) {
      evt.preventDefault();
      evt.stopPropagation();
    }
  }
};

prototype$2.filter = function(filter) {
  var s = stream(filter);
  this.targets().add(s);
  return s;
};

prototype$2.apply = function(apply) {
  var s = stream(null, apply);
  this.targets().add(s);
  return s;
};

prototype$2.merge = function() {
  var s = stream();

  this.targets().add(s);
  for (var i=0, n=arguments.length; i<n; ++i) {
    arguments[i].targets().add(s);
  }

  return s;
};

prototype$2.throttle = function(pause) {
  var t = -1;
  return this.filter(function() {
    var now = Date.now();
    if ((now - t) > pause) {
      t = now;
      return 1;
    } else {
      return 0;
    }
  });
};

prototype$2.debounce = function(delay) {
  var s = stream();

  this.targets().add(stream(null, null,
    debounce(delay, function(e) {
      var df = e.dataflow;
      s.receive(e);
      if (df && df.run) df.run();
    })
  ));

  return s;
};

prototype$2.between = function(a, b) {
  var active = false;
  a.targets().add(stream(null, null, function() { active = true; }));
  b.targets().add(stream(null, null, function() { active = false; }));
  return this.filter(function() { return active; });
};

/**
 * Create a new event stream from an event source.
 * @param {object} source - The event source to monitor. The input must
 *  support the addEventListener method.
 * @param {string} type - The event type.
 * @param {function(object): boolean} [filter] - Event filter function.
 * @param {function(object): *} [apply] - Event application function.
 *   If provided, this function will be invoked and the result will be
 *   used as the downstream event value.
 * @return {EventStream}
 */
function events(source, type, filter, apply) {
  var df = this,
      s = stream(filter, apply),
      send = function(e) {
        e.dataflow = df;
        try {
          s.receive(e);
        } catch (error) {
          df.error(error);
        } finally {
          df.run();
        }
      },
      sources;

  if (typeof source === 'string' && typeof document !== 'undefined') {
    sources = document.querySelectorAll(source);
  } else {
    sources = array(source);
  }

  for (var i=0, n=sources.length; i<n; ++i) {
    sources[i].addEventListener(type, send);
  }

  return s;
}

// Matches absolute URLs with optional protocol
//   https://...    file://...    //...
const protocol_re = /^([A-Za-z]+:)?\/\//;

// Matches allowed URIs. From https://github.com/cure53/DOMPurify/blob/master/src/regexp.js with added file://
const allowed_re = /^(?:(?:(?:f|ht)tps?|mailto|tel|callto|cid|xmpp|file):|[^a-z]|[a-z+.\-]+(?:[^a-z+.\-:]|$))/i; // eslint-disable-line no-useless-escape
const whitespace_re = /[\u0000-\u0020\u00A0\u1680\u180E\u2000-\u2029\u205f\u3000]/g; // eslint-disable-line no-control-regex


// Special treatment in node.js for the file: protocol
const fileProtocol = 'file://';

/**
 * Factory for a loader constructor that provides methods for requesting
 * files from either the network or disk, and for sanitizing request URIs.
 * @param {function} fetch - The Fetch API for HTTP network requests.
 *   If null or undefined, HTTP loading will be disabled.
 * @param {object} fs - The file system interface for file loading.
 *   If null or undefined, local file loading will be disabled.
 * @return {function} A loader constructor with the following signature:
 *   param {object} [options] - Optional default loading options to use.
 *   return {object} - A new loader instance.
 */
function loaderFactory(fetch, fs) {
  return function(options) {
    return {
      options: options || {},
      sanitize: sanitize,
      load: load,
      fileAccess: !!fs,
      file: fileLoader(fs),
      http: httpLoader(fetch)
    };
  };
}

/**
 * Load an external resource, typically either from the web or from the local
 * filesystem. This function uses {@link sanitize} to first sanitize the uri,
 * then calls either {@link http} (for web requests) or {@link file} (for
 * filesystem loading).
 * @param {string} uri - The resource indicator (e.g., URL or filename).
 * @param {object} [options] - Optional loading options. These options will
 *   override any existing default options.
 * @return {Promise} - A promise that resolves to the loaded content.
 */
async function load(uri, options) {
  const opt = await this.sanitize(uri, options),
        url = opt.href;

  return opt.localFile
    ? this.file(url)
    : this.http(url, options);
}

/**
 * URI sanitizer function.
 * @param {string} uri - The uri (url or filename) to sanity check.
 * @param {object} options - An options hash.
 * @return {Promise} - A promise that resolves to an object containing
 *  sanitized uri data, or rejects it the input uri is deemed invalid.
 *  The properties of the resolved object are assumed to be
 *  valid attributes for an HTML 'a' tag. The sanitized uri *must* be
 *  provided by the 'href' property of the returned object.
 */
async function sanitize(uri, options) {
  options = extend({}, this.options, options);

  const fileAccess = this.fileAccess,
        result = {href: null};

  let isFile, loadFile, base;

  const isAllowed = allowed_re.test(uri.replace(whitespace_re, ''));

  if (uri == null || typeof uri !== 'string' || !isAllowed) {
    error('Sanitize failure, invalid URI: ' + $(uri));
  }

  const hasProtocol = protocol_re.test(uri);

  // if relative url (no protocol/host), prepend baseURL
  if ((base = options.baseURL) && !hasProtocol) {
    // Ensure that there is a slash between the baseURL (e.g. hostname) and url
    if (!uri.startsWith('/') && base[base.length-1] !== '/') {
      uri = '/' + uri;
    }
    uri = base + uri;
  }

  // should we load from file system?
  loadFile = (isFile = uri.startsWith(fileProtocol))
    || options.mode === 'file'
    || options.mode !== 'http' && !hasProtocol && fileAccess;

  if (isFile) {
    // strip file protocol
    uri = uri.slice(fileProtocol.length);
  } else if (uri.startsWith('//')) {
    if (options.defaultProtocol === 'file') {
      // if is file, strip protocol and set loadFile flag
      uri = uri.slice(2);
      loadFile = true;
    } else {
      // if relative protocol (starts with '//'), prepend default protocol
      uri = (options.defaultProtocol || 'http') + ':' + uri;
    }
  }

  // set non-enumerable mode flag to indicate local file load
  Object.defineProperty(result, 'localFile', {value: !!loadFile});

  // set uri
  result.href = uri;

  // set default result target, if specified
  if (options.target) {
    result.target = options.target + '';
  }

  // set default result rel, if specified (#1542)
  if (options.rel) {
    result.rel = options.rel + '';
  }

  // return
  return result;
}

/**
 * File system loader factory.
 * @param {object} fs - The file system interface.
 * @return {function} - A file loader with the following signature:
 *   param {string} filename - The file system path to load.
 *   param {string} filename - The file system path to load.
 *   return {Promise} A promise that resolves to the file contents.
 */
function fileLoader(fs) {
  return fs
    ? function(filename) {
        return new Promise(function(accept, reject) {
          fs.readFile(filename, function(error, data) {
            if (error) reject(error);
            else accept(data);
          });
        });
      }
    : fileReject;
}

/**
 * Default file system loader that simply rejects.
 */
async function fileReject() {
  error('No file system access.');
}

/**
 * HTTP request handler factory.
 * @param {function} fetch - The Fetch API method.
 * @return {function} - An http loader with the following signature:
 *   param {string} url - The url to request.
 *   param {object} options - An options hash.
 *   return {Promise} - A promise that resolves to the file contents.
 */
function httpLoader(fetch) {
  return fetch
    ? async function(url, options) {
        const opt = extend({}, this.options.http, options),
              type = options && options.response,
              response = await fetch(url, opt);

        return !response.ok
          ? error(response.status + '' + response.statusText)
          : isFunction(response[type]) ? response[type]()
          : response.text();
      }
    : httpReject;
}

/**
 * Default http request handler that simply rejects.
 */
async function httpReject() {
  error('No HTTP fetch method available.');
}

var typeParsers = {
  boolean: toBoolean,
  integer: toNumber,
  number:  toNumber,
  date:    toDate,
  string:  toString,
  unknown: identity
};

var typeTests = [
  isBoolean$1,
  isInteger,
  isNumber$1,
  isDate$1
];

var typeList = [
  'boolean',
  'integer',
  'number',
  'date'
];

function inferType(values, field) {
  if (!values || !values.length) return 'unknown';

  var value, i, j, t = 0,
      n = values.length,
      m = typeTests.length,
      a = typeTests.map(function(_, i) { return i + 1; });

  for (i=0, n=values.length; i<n; ++i) {
    value = field ? values[i][field] : values[i];
    for (j=0; j<m; ++j) {
      if (a[j] && isValid(value) && !typeTests[j](value)) {
        a[j] = 0;
        ++t;
        if (t === typeTests.length) return 'string';
      }
    }
  }

  t = a.reduce(function(u, v) { return u === 0 ? v : u; }, 0) - 1;
  return typeList[t];
}

function inferTypes(data, fields) {
  return fields.reduce(function(types, field) {
    types[field] = inferType(data, field);
    return types;
  }, {});
}

// -- Type Checks ----

function isValid(_) {
  return _ != null && _ === _;
}

function isBoolean$1(_) {
  return _ === 'true' || _ === 'false' || _ === true || _ === false;
}

function isDate$1(_) {
  return !Number.isNaN(Date.parse(_));
}

function isNumber$1(_) {
  return !Number.isNaN(+_) && !(_ instanceof Date);
}

function isInteger(_) {
  return isNumber$1(_) && Number.isInteger(+_);
}

function delimitedFormat(delimiter) {
  const parse = function(data, format) {
    const delim = {delimiter: delimiter};
    return dsv(data, format ? extend(format, delim) : delim);
  };

  parse.responseType = 'text';

  return parse;
}

function dsv(data, format) {
  if (format.header) {
    data = format.header
      .map($)
      .join(format.delimiter) + '\n' + data;
  }
  return dsvFormat(format.delimiter).parse(data + '');
}

dsv.responseType = 'text';

function isBuffer(_) {
  return (typeof Buffer === 'function' && isFunction(Buffer.isBuffer))
    ? Buffer.isBuffer(_) : false;
}

function json(data, format) {
  const prop = (format && format.property) ? field(format.property) : identity;
  return isObject(data) && !isBuffer(data)
    ? parseJSON(prop(data))
    : prop(JSON.parse(data));
}

json.responseType = 'json';

function parseJSON(data, format) {
  return (format && format.copy)
    ? JSON.parse(JSON.stringify(data))
    : data;
}

const filters = {
  interior: (a, b) => a !== b,
  exterior: (a, b) => a === b
};

function topojson(data, format) {
  let method, object, property, filter;
  data = json(data, format);

  if (format && format.feature) {
    method = feature;
    property = format.feature;
  } else if (format && format.mesh) {
    method = mesh;
    property = format.mesh;
    filter = filters[format.filter];
  } else {
    error('Missing TopoJSON feature or mesh parameter.');
  }

  object = (object = data.objects[property])
    ? method(data, object, filter)
    : error('Invalid TopoJSON object: ' + property);

  return object && object.features || [object];
}

topojson.responseType = 'json';

const format = {
  dsv: dsv,
  csv: delimitedFormat(','),
  tsv: delimitedFormat('\t'),
  json: json,
  topojson: topojson
};

function formats(name, reader) {
  if (arguments.length > 1) {
    format[name] = reader;
    return this;
  } else {
    return hasOwnProperty(format, name) ? format[name] : null;
  }
}

function responseType(type) {
  const f = formats(type);
  return f && f.responseType || 'text';
}

function read(data, schema, dateParse) {
  schema = schema || {};

  const reader = formats(schema.type || 'json');
  if (!reader) error('Unknown data format type: ' + schema.type);

  data = reader(data, schema);
  if (schema.parse) parse(data, schema.parse, dateParse);

  if (hasOwnProperty(data, 'columns')) delete data.columns;
  return data;
}

function parse(data, types, dateParse) {
  if (!data.length) return; // early exit for empty data

  dateParse = dateParse || timeParse$1;

  var fields = data.columns || Object.keys(data[0]),
      parsers, datum, field, i, j, n, m;

  if (types === 'auto') types = inferTypes(data, fields);

  fields = Object.keys(types);
  parsers = fields.map(function(field) {
    var type = types[field],
        parts, pattern;

    if (type && (type.indexOf('date:') === 0 || type.indexOf('utc:') === 0)) {
      parts = type.split(/:(.+)?/, 2);  // split on first :
      pattern = parts[1];

      if ((pattern[0] === '\'' && pattern[pattern.length-1] === '\'') ||
          (pattern[0] === '"'  && pattern[pattern.length-1] === '"')) {
        pattern = pattern.slice(1, -1);
      }

      return parts[0] === 'utc' ? utcParse$1(pattern) : dateParse(pattern);
    }

    if (!typeParsers[type]) {
      throw Error('Illegal format pattern: ' + field + ':' + type);
    }

    return typeParsers[type];
  });

  for (i=0, n=data.length, m=fields.length; i<n; ++i) {
    datum = data[i];
    for (j=0; j<m; ++j) {
      field = fields[j];
      datum[field] = parsers[j](datum[field]);
    }
  }
}

var loader = loaderFactory(
  typeof fetch !== 'undefined' && fetch, // use built-in fetch API
  null // no file system access
);

const parse$1 = read;

/**
 * Ingests new data into the dataflow. First parses the data using the
 * vega-loader read method, then pulses a changeset to the target operator.
 * @param {Operator} target - The Operator to target with ingested data,
 *   typically a Collect transform instance.
 * @param {*} data - The input data, prior to parsing. For JSON this may
 *   be a string or an object. For CSV, TSV, etc should be a string.
 * @param {object} format - The data format description for parsing
 *   loaded data. This object is passed to the vega-loader read method.
 * @returns {Dataflow}
 */
function ingest$1(target, data, format) {
  return this.pulse(target, this.changeset().insert(parse$1(data, format)));
}

/**
 * Request data from an external source, parse it, and return a Promise.
 * @param {string} url - The URL from which to load the data. This string
 *   is passed to the vega-loader load method.
 * @param {object} [format] - The data format description for parsing
 *   loaded data. This object is passed to the vega-loader read method.
 * @return {Promise} A Promise that resolves upon completion of the request.
 *   The resolved object contains the following properties:
 *   - data: an array of parsed data (or null upon error)
 *   - status: a code for success (0), load fail (-1), or parse fail (-2)
 */
async function request(url, format) {
  const df = this;
  let status = 0, data;

  try {
    data = await df.loader().load(url, {
      context: 'dataflow',
      response: responseType(format && format.type)
    });
    try {
      data = parse$1(data, format);
    } catch (err) {
      status = -2;
      df.warn('Data ingestion failed', url, err);
    }
  } catch (err) {
    status = -1;
    df.warn('Loading failed', url, err);
  }

  return {data, status};
}

async function preload(target, url, format) {
  const df = this,
        pending = df._pending || loadPending(df);

  pending.requests += 1;

  const res = await df.request(url, format);
  df.pulse(target, df.changeset().remove(truthy).insert(res.data || []));

  pending.done();
  return res;
}

function loadPending(df) {
  var pending = new Promise(function(a) { accept = a; }),
      accept;

  pending.requests = 0;

  pending.done = function() {
    if (--pending.requests === 0) {
      df._pending = null;
      accept(df);
    }
  };

  return (df._pending = pending);
}

var SKIP$1 = {skip: true};

/**
 * Perform operator updates in response to events. Applies an
 * update function to compute a new operator value. If the update function
 * returns a {@link ChangeSet}, the operator will be pulsed with those tuple
 * changes. Otherwise, the operator value will be updated to the return value.
 * @param {EventStream|Operator} source - The event source to react to.
 *   This argument can be either an EventStream or an Operator.
 * @param {Operator|function(object):Operator} target - The operator to update.
 *   This argument can either be an Operator instance or (if the source
 *   argument is an EventStream), a function that accepts an event object as
 *   input and returns an Operator to target.
 * @param {function(Parameters,Event): *} [update] - Optional update function
 *   to compute the new operator value, or a literal value to set. Update
 *   functions expect to receive a parameter object and event as arguments.
 *   This function can either return a new operator value or (if the source
 *   argument is an EventStream) a {@link ChangeSet} instance to pulse
 *   the target operator with tuple changes.
 * @param {object} [params] - The update function parameters.
 * @param {object} [options] - Additional options hash. If not overridden,
 *   updated operators will be skipped by default.
 * @param {boolean} [options.skip] - If true, the operator will
 *  be skipped: it will not be evaluated, but its dependents will be.
 * @param {boolean} [options.force] - If true, the operator will
 *   be re-evaluated even if its value has not changed.
 * @return {Dataflow}
 */
function on(source, target, update, params, options) {
  var fn = source instanceof Operator ? onOperator : onStream;
  fn(this, source, target, update, params, options);
  return this;
}

function onStream(df, stream, target, update, params, options) {
  var opt = extend({}, options, SKIP$1), func, op;

  if (!isFunction(target)) target = constant(target);

  if (update === undefined) {
    func = e => df.touch(target(e));
  } else if (isFunction(update)) {
    op = new Operator(null, update, params, false);
    func = e => {
      op.evaluate(e);
      const t = target(e), v = op.value;
      isChangeSet(v) ? df.pulse(t, v, options) : df.update(t, v, opt);
    };
  } else {
    func = e => df.update(target(e), update, opt);
  }

  stream.apply(func);
}

function onOperator(df, source, target, update, params, options) {
  if (update === undefined) {
    source.targets().add(target);
  } else {
    const opt = options || {},
          op = new Operator(null, updater(target, update), params, false);
    op.modified(opt.force);
    op.rank = source.rank;       // immediately follow source
    source.targets().add(op);    // add dependency

    if (target) {
      op.skip(true);             // skip first invocation
      op.value = target.value;   // initialize value
      op.targets().add(target);  // chain dependencies
      df.connect(target, [op]);  // rerank as needed, #1672
    }
  }
}

function updater(target, update) {
  update = isFunction(update) ? update : constant(update);
  return target
    ? function(_, pulse) {
        const value = update(_, pulse);
        if (!target.skip()) {
          target.skip(value !== this.value).value = value;
        }
        return value;
      }
    : update;
}

/**
 * Assigns a rank to an operator. Ranks are assigned in increasing order
 * by incrementing an internal rank counter.
 * @param {Operator} op - The operator to assign a rank.
 */
function rank(op) {
  op.rank = ++this._rank;
}

/**
 * Re-ranks an operator and all downstream target dependencies. This
 * is necessary when upstream dependencies of higher rank are added to
 * a target operator.
 * @param {Operator} op - The operator to re-rank.
 */
function rerank(op) {
  var queue = [op],
      cur, list, i;

  while (queue.length) {
    this.rank(cur = queue.pop());
    if (list = cur._targets) {
      for (i=list.length; --i >= 0;) {
        queue.push(cur = list[i]);
        if (cur === op) error('Cycle detected in dataflow graph.');
      }
    }
  }
}

/**
 * Sentinel value indicating pulse propagation should stop.
 */
var StopPropagation = {};

// Pulse visit type flags
var ADD       = (1 << 0),
    REM       = (1 << 1),
    MOD       = (1 << 2),
    ADD_REM   = ADD | REM,
    ADD_MOD   = ADD | MOD,
    ALL       = ADD | REM | MOD,
    REFLOW    = (1 << 3),
    SOURCE    = (1 << 4),
    NO_SOURCE = (1 << 5),
    NO_FIELDS = (1 << 6);

/**
 * A Pulse enables inter-operator communication during a run of the
 * dataflow graph. In addition to the current timestamp, a pulse may also
 * contain a change-set of added, removed or modified data tuples, as well as
 * a pointer to a full backing data source. Tuple change sets may not
 * be fully materialized; for example, to prevent needless array creation
 * a change set may include larger arrays and corresponding filter functions.
 * The pulse provides a {@link visit} method to enable proper and efficient
 * iteration over requested data tuples.
 *
 * In addition, each pulse can track modification flags for data tuple fields.
 * Responsible transform operators should call the {@link modifies} method to
 * indicate changes to data fields. The {@link modified} method enables
 * querying of this modification state.
 *
 * @constructor
 * @param {Dataflow} dataflow - The backing dataflow instance.
 * @param {number} stamp - The current propagation timestamp.
 * @param {string} [encode] - An optional encoding set name, which is then
 *   accessible as Pulse.encode. Operators can respond to (or ignore) this
 *   setting as appropriate. This parameter can be used in conjunction with
 *   the Encode transform in the vega-encode module.
 */
function Pulse(dataflow, stamp, encode) {
  this.dataflow = dataflow;
  this.stamp = stamp == null ? -1 : stamp;
  this.add = [];
  this.rem = [];
  this.mod = [];
  this.fields = null;
  this.encode = encode || null;
}

var prototype$3 = Pulse.prototype;

/**
 * Sentinel value indicating pulse propagation should stop.
 */
prototype$3.StopPropagation = StopPropagation;

/**
 * Boolean flag indicating ADD (added) tuples.
 */
prototype$3.ADD = ADD;

/**
 * Boolean flag indicating REM (removed) tuples.
 */
prototype$3.REM = REM;

/**
 * Boolean flag indicating MOD (modified) tuples.
 */
prototype$3.MOD = MOD;

/**
 * Boolean flag indicating ADD (added) and REM (removed) tuples.
 */
prototype$3.ADD_REM = ADD_REM;

/**
 * Boolean flag indicating ADD (added) and MOD (modified) tuples.
 */
prototype$3.ADD_MOD = ADD_MOD;

/**
 * Boolean flag indicating ADD, REM and MOD tuples.
 */
prototype$3.ALL = ALL;

/**
 * Boolean flag indicating all tuples in a data source
 * except for the ADD, REM and MOD tuples.
 */
prototype$3.REFLOW = REFLOW;

/**
 * Boolean flag indicating a 'pass-through' to a
 * backing data source, ignoring ADD, REM and MOD tuples.
 */
prototype$3.SOURCE = SOURCE;

/**
 * Boolean flag indicating that source data should be
 * suppressed when creating a forked pulse.
 */
prototype$3.NO_SOURCE = NO_SOURCE;

/**
 * Boolean flag indicating that field modifications should be
 * suppressed when creating a forked pulse.
 */
prototype$3.NO_FIELDS = NO_FIELDS;

/**
 * Creates a new pulse based on the values of this pulse.
 * The dataflow, time stamp and field modification values are copied over.
 * By default, new empty ADD, REM and MOD arrays are created.
 * @param {number} flags - Integer of boolean flags indicating which (if any)
 *   tuple arrays should be copied to the new pulse. The supported flag values
 *   are ADD, REM and MOD. Array references are copied directly: new array
 *   instances are not created.
 * @return {Pulse} - The forked pulse instance.
 * @see init
 */
prototype$3.fork = function(flags) {
  return new Pulse(this.dataflow).init(this, flags);
};

/**
 * Creates a copy of this pulse with new materialized array
 * instances for the ADD, REM, MOD, and SOURCE arrays.
 * The dataflow, time stamp and field modification values are copied over.
 * @return {Pulse} - The cloned pulse instance.
 * @see init
 */
prototype$3.clone = function() {
  var p = this.fork(ALL);
  p.add = p.add.slice();
  p.rem = p.rem.slice();
  p.mod = p.mod.slice();
  if (p.source) p.source = p.source.slice();
  return p.materialize(ALL | SOURCE);
};

/**
 * Returns a pulse that adds all tuples from a backing source. This is
 * useful for cases where operators are added to a dataflow after an
 * upstream data pipeline has already been processed, ensuring that
 * new operators can observe all tuples within a stream.
 * @return {Pulse} - A pulse instance with all source tuples included
 *   in the add array. If the current pulse already has all source
 *   tuples in its add array, it is returned directly. If the current
 *   pulse does not have a backing source, it is returned directly.
 */
prototype$3.addAll = function() {
  var p = this;
  if (!this.source || this.source.length === this.add.length) {
    return p;
  } else {
    p = new Pulse(this.dataflow).init(this);
    p.add = p.source;
    return p;
  }
};

/**
 * Initialize this pulse based on the values of another pulse. This method
 * is used internally by {@link fork} to initialize a new forked tuple.
 * The dataflow, time stamp and field modification values are copied over.
 * By default, new empty ADD, REM and MOD arrays are created.
 * @param {Pulse} src - The source pulse to copy from.
 * @param {number} flags - Integer of boolean flags indicating which (if any)
 *   tuple arrays should be copied to the new pulse. The supported flag values
 *   are ADD, REM and MOD. Array references are copied directly: new array
 *   instances are not created. By default, source data arrays are copied
 *   to the new pulse. Use the NO_SOURCE flag to enforce a null source.
 * @return {Pulse} - Returns this Pulse instance.
 */
prototype$3.init = function(src, flags) {
  var p = this;
  p.stamp = src.stamp;
  p.encode = src.encode;

  if (src.fields && !(flags & NO_FIELDS)) {
    p.fields = src.fields;
  }

  if (flags & ADD) {
    p.addF = src.addF;
    p.add = src.add;
  } else {
    p.addF = null;
    p.add = [];
  }

  if (flags & REM) {
    p.remF = src.remF;
    p.rem = src.rem;
  } else {
    p.remF = null;
    p.rem = [];
  }

  if (flags & MOD) {
    p.modF = src.modF;
    p.mod = src.mod;
  } else {
    p.modF = null;
    p.mod = [];
  }

  if (flags & NO_SOURCE) {
    p.srcF = null;
    p.source = null;
  } else {
    p.srcF = src.srcF;
    p.source = src.source;
  }

  return p;
};

/**
 * Schedules a function to run after pulse propagation completes.
 * @param {function} func - The function to run.
 */
prototype$3.runAfter = function(func) {
  this.dataflow.runAfter(func);
};

/**
 * Indicates if tuples have been added, removed or modified.
 * @param {number} [flags] - The tuple types (ADD, REM or MOD) to query.
 *   Defaults to ALL, returning true if any tuple type has changed.
 * @return {boolean} - Returns true if one or more queried tuple types have
 *   changed, false otherwise.
 */
prototype$3.changed = function(flags) {
  var f = flags || ALL;
  return ((f & ADD) && this.add.length)
      || ((f & REM) && this.rem.length)
      || ((f & MOD) && this.mod.length);
};

/**
 * Forces a "reflow" of tuple values, such that all tuples in the backing
 * source are added to the MOD set, unless already present in the ADD set.
 * @param {boolean} [fork=false] - If true, returns a forked copy of this
 *   pulse, and invokes reflow on that derived pulse.
 * @return {Pulse} - The reflowed pulse instance.
 */
prototype$3.reflow = function(fork) {
  if (fork) return this.fork(ALL).reflow();

  var len = this.add.length,
      src = this.source && this.source.length;
  if (src && src !== len) {
    this.mod = this.source;
    if (len) this.filter(MOD, filter(this, ADD));
  }
  return this;
};

/**
 * Marks one or more data field names as modified to assist dependency
 * tracking and incremental processing by transform operators.
 * @param {string|Array<string>} _ - The field(s) to mark as modified.
 * @return {Pulse} - This pulse instance.
 */
prototype$3.modifies = function(_) {
  var hash = this.fields || (this.fields = {});
  if (isArray(_)) {
    _.forEach(f => hash[f] = true);
  } else {
    hash[_] = true;
  }
  return this;
};

/**
 * Checks if one or more data fields have been modified during this pulse
 * propagation timestamp.
 * @param {string|Array<string>} _ - The field(s) to check for modified.
 * @param {boolean} nomod - If true, will check the modified flag even if
 *   no mod tuples exist. If false (default), mod tuples must be present.
 * @return {boolean} - Returns true if any of the provided fields has been
 *   marked as modified, false otherwise.
 */
prototype$3.modified = function(_, nomod) {
  var fields = this.fields;
  return !((nomod || this.mod.length) && fields) ? false
    : !arguments.length ? !!fields
    : isArray(_) ? _.some(function(f) { return fields[f]; })
    : fields[_];
};

/**
 * Adds a filter function to one more tuple sets. Filters are applied to
 * backing tuple arrays, to determine the actual set of tuples considered
 * added, removed or modified. They can be used to delay materialization of
 * a tuple set in order to avoid expensive array copies. In addition, the
 * filter functions can serve as value transformers: unlike standard predicate
 * function (which return boolean values), Pulse filters should return the
 * actual tuple value to process. If a tuple set is already filtered, the
 * new filter function will be appended into a conjuntive ('and') query.
 * @param {number} flags - Flags indicating the tuple set(s) to filter.
 * @param {function(*):object} filter - Filter function that will be applied
 *   to the tuple set array, and should return a data tuple if the value
 *   should be included in the tuple set, and falsy (or null) otherwise.
 * @return {Pulse} - Returns this pulse instance.
 */
prototype$3.filter = function(flags, filter) {
  var p = this;
  if (flags & ADD) p.addF = addFilter(p.addF, filter);
  if (flags & REM) p.remF = addFilter(p.remF, filter);
  if (flags & MOD) p.modF = addFilter(p.modF, filter);
  if (flags & SOURCE) p.srcF = addFilter(p.srcF, filter);
  return p;
};

function addFilter(a, b) {
  return a ? function(t,i) { return a(t,i) && b(t,i); } : b;
}

/**
 * Materialize one or more tuple sets in this pulse. If the tuple set(s) have
 * a registered filter function, it will be applied and the tuple set(s) will
 * be replaced with materialized tuple arrays.
 * @param {number} flags - Flags indicating the tuple set(s) to materialize.
 * @return {Pulse} - Returns this pulse instance.
 */
prototype$3.materialize = function(flags) {
  flags = flags || ALL;
  var p = this;
  if ((flags & ADD) && p.addF) {
    p.add = materialize(p.add, p.addF);
    p.addF = null;
  }
  if ((flags & REM) && p.remF) {
    p.rem = materialize(p.rem, p.remF);
    p.remF = null;
  }
  if ((flags & MOD) && p.modF) {
    p.mod = materialize(p.mod, p.modF);
    p.modF = null;
  }
  if ((flags & SOURCE) && p.srcF) {
    p.source = p.source.filter(p.srcF);
    p.srcF = null;
  }
  return p;
};

function materialize(data, filter) {
  var out = [];
  visitArray(data, filter, function(_) { out.push(_); });
  return out;
}

function filter(pulse, flags) {
  var map = {};
  pulse.visit(flags, function(t) { map[tupleid(t)] = 1; });
  return function(t) { return map[tupleid(t)] ? null : t; };
}

/**
 * Visit one or more tuple sets in this pulse.
 * @param {number} flags - Flags indicating the tuple set(s) to visit.
 *   Legal values are ADD, REM, MOD and SOURCE (if a backing data source
 *   has been set).
 * @param {function(object):*} - Visitor function invoked per-tuple.
 * @return {Pulse} - Returns this pulse instance.
 */
prototype$3.visit = function(flags, visitor) {
  var p = this, v = visitor, src, sum;

  if (flags & SOURCE) {
    visitArray(p.source, p.srcF, v);
    return p;
  }

  if (flags & ADD) visitArray(p.add, p.addF, v);
  if (flags & REM) visitArray(p.rem, p.remF, v);
  if (flags & MOD) visitArray(p.mod, p.modF, v);

  if ((flags & REFLOW) && (src = p.source)) {
    sum = p.add.length + p.mod.length;
    if (sum === src.length) ; else if (sum) {
      visitArray(src, filter(p, ADD_MOD), v);
    } else {
      // if no add/rem/mod tuples, visit source
      visitArray(src, p.srcF, v);
    }
  }

  return p;
};

/**
 * Represents a set of multiple pulses. Used as input for operators
 * that accept multiple pulses at a time. Contained pulses are
 * accessible via the public "pulses" array property. This pulse doe
 * not carry added, removed or modified tuples directly. However,
 * the visit method can be used to traverse all such tuples contained
 * in sub-pulses with a timestamp matching this parent multi-pulse.
 * @constructor
 * @param {Dataflow} dataflow - The backing dataflow instance.
 * @param {number} stamp - The timestamp.
 * @param {Array<Pulse>} pulses - The sub-pulses for this multi-pulse.
 */
function MultiPulse(dataflow, stamp, pulses, encode) {
  var p = this,
      c = 0,
      pulse, hash, i, n, f;

  this.dataflow = dataflow;
  this.stamp = stamp;
  this.fields = null;
  this.encode = encode || null;
  this.pulses = pulses;

  for (i=0, n=pulses.length; i<n; ++i) {
    pulse = pulses[i];
    if (pulse.stamp !== stamp) continue;

    if (pulse.fields) {
      hash = p.fields || (p.fields = {});
      for (f in pulse.fields) { hash[f] = 1; }
    }

    if (pulse.changed(p.ADD)) c |= p.ADD;
    if (pulse.changed(p.REM)) c |= p.REM;
    if (pulse.changed(p.MOD)) c |= p.MOD;
  }

  this.changes = c;
}

var prototype$4 = inherits(MultiPulse, Pulse);

/**
 * Creates a new pulse based on the values of this pulse.
 * The dataflow, time stamp and field modification values are copied over.
 * @return {Pulse}
 */
prototype$4.fork = function(flags) {
  var p = new Pulse(this.dataflow).init(this, flags & this.NO_FIELDS);
  if (flags !== undefined) {
    if (flags & p.ADD) {
      this.visit(p.ADD, function(t) { return p.add.push(t); });
    }
    if (flags & p.REM) {
      this.visit(p.REM, function(t) { return p.rem.push(t); });
    }
    if (flags & p.MOD) {
      this.visit(p.MOD, function(t) { return p.mod.push(t); });
    }
  }
  return p;
};

prototype$4.changed = function(flags) {
  return this.changes & flags;
};

prototype$4.modified = function(_) {
  var p = this, fields = p.fields;
  return !(fields && (p.changes & p.MOD)) ? 0
    : isArray(_) ? _.some(function(f) { return fields[f]; })
    : fields[_];
};

prototype$4.filter = function() {
  error('MultiPulse does not support filtering.');
};

prototype$4.materialize = function() {
  error('MultiPulse does not support materialization.');
};

prototype$4.visit = function(flags, visitor) {
  var p = this,
      pulses = p.pulses,
      n = pulses.length,
      i = 0;

  if (flags & p.SOURCE) {
    for (; i<n; ++i) {
      pulses[i].visit(flags, visitor);
    }
  } else {
    for (; i<n; ++i) {
      if (pulses[i].stamp === p.stamp) {
        pulses[i].visit(flags, visitor);
      }
    }
  }

  return p;
};

/* eslint-disable require-atomic-updates */

/**
 * Evaluates the dataflow and returns a Promise that resolves when pulse
 * propagation completes. This method will increment the current timestamp
 * and process all updated, pulsed and touched operators. When invoked for
 * the first time, all registered operators will be processed. This method
 * should not be invoked by third-party clients, use {@link runAsync} or
 * {@link run} instead.
 * @param {string} [encode] - The name of an encoding set to invoke during
 *   propagation. This value is added to generated Pulse instances;
 *   operators can then respond to (or ignore) this setting as appropriate.
 *   This parameter can be used in conjunction with the Encode transform in
 *   the vega-encode package.
 * @param {function} [prerun] - An optional callback function to invoke
 *   immediately before dataflow evaluation commences.
 * @param {function} [postrun] - An optional callback function to invoke
 *   after dataflow evaluation completes. The callback will be invoked
 *   after those registered via {@link runAfter}.
 * @return {Promise} - A promise that resolves to this dataflow after
 *   evaluation completes.
 */
async function evaluate(encode, prerun, postrun) {
  const df = this,
        level = df.logLevel(),
        async = [];

  // if the pulse value is set, this is a re-entrant call
  if (df._pulse) return reentrant(df);

  // wait for pending datasets to load
  if (df._pending) {
    await df._pending;
  }

  // invoke prerun function, if provided
  if (prerun) await asyncCallback(df, prerun);

  // exit early if there are no updates
  if (!df._touched.length) {
    df.info('Dataflow invoked, but nothing to do.');
    return df;
  }

  // increment timestamp clock
  let stamp = ++df._clock,
      count = 0, op, next, dt, error;

  // set the current pulse
  df._pulse = new Pulse(df, stamp, encode);

  if (level >= Info) {
    dt = Date.now();
    df.debug('-- START PROPAGATION (' + stamp + ') -----');
  }

  // initialize priority queue, reset touched operators
  df._touched.forEach(op => df._enqueue(op, true));
  df._touched = UniqueList(id);

  try {
    while (df._heap.size() > 0) {
      // dequeue operator with highest priority
      op = df._heap.pop();

      // re-queue if rank changed
      if (op.rank !== op.qrank) { df._enqueue(op, true); continue; }

      // otherwise, evaluate the operator
      next = op.run(df._getPulse(op, encode));

      if (next.then) {
        // await if operator returns a promise directly
        next = await next;
      } else if (next.async) {
        // queue parallel asynchronous execution
        async.push(next.async);
        next = StopPropagation;
      }

      if (level >= Debug) {
        df.debug(op.id, next === StopPropagation ? 'STOP' : next, op);
      }

      // propagate evaluation, enqueue dependent operators
      if (next !== StopPropagation) {
        if (op._targets) op._targets.forEach(op => df._enqueue(op));
      }

      // increment visit counter
      ++count;
    }
  } catch (err) {
    df._heap.clear();
    error = err;
  }

  // reset pulse map
  df._input = {};
  df._pulse = null;

  if (level >= Info) {
    dt = Date.now() - dt;
    df.info('> Pulse ' + stamp + ': ' + count + ' operators; ' + dt + 'ms');
  }

  if (error) {
    df._postrun = [];
    df.error(error);
  }

  // invoke callbacks queued via runAfter
  if (df._postrun.length) {
    const pr = df._postrun.sort((a, b) => b.priority - a.priority);
    df._postrun = [];
    for (let i=0; i<pr.length; ++i) {
      await asyncCallback(df, pr[i].callback);
    }
  }

  // invoke postrun function, if provided
  if (postrun) await asyncCallback(df, postrun);

  // handle non-blocking asynchronous callbacks
  if (async.length) {
    Promise.all(async).then(cb => df.runAsync(null, () => {
      cb.forEach(f => { try { f(df); } catch (err) { df.error(err); } });
    }));
  }

  return df;
}

/**
 * Queues dataflow evaluation to run once any other queued evaluations have
 * completed and returns a Promise that resolves when the queued pulse
 * propagation completes. If provided, a callback function will be invoked
 * immediately before evaluation commences. This method will ensure a
 * separate evaluation is invoked for each time it is called.
 * @param {string} [encode] - The name of an encoding set to invoke during
 *   propagation. This value is added to generated Pulse instances;
 *   operators can then respond to (or ignore) this setting as appropriate.
 *   This parameter can be used in conjunction with the Encode transform in
 *   the vega-encode package.
 * @param {function} [prerun] - An optional callback function to invoke
 *   immediately before dataflow evaluation commences.
 * @param {function} [postrun] - An optional callback function to invoke
 *   after dataflow evaluation completes. The callback will be invoked
 *   after those registered via {@link runAfter}.
 * @return {Promise} - A promise that resolves to this dataflow after
 *   evaluation completes.
 */
async function runAsync(encode, prerun, postrun) {
  // await previously queued functions
  while (this._running) await this._running;

  // run dataflow, manage running promise
  const clear = () => this._running = null;
  (this._running = this.evaluate(encode, prerun, postrun))
    .then(clear, clear);

  return this._running;
}

/**
 * Requests dataflow evaluation and the immediately returns this dataflow
 * instance. If there are pending data loading or other asynchronous
 * operations, the dataflow will evaluate asynchronously after this method
 * has been invoked. To track when dataflow evaluation completes, use the
 * {@link runAsync} method instead. This method will raise an error if
 * invoked while the dataflow is already in the midst of evaluation.
 * @param {string} [encode] - The name of an encoding set to invoke during
 *   propagation. This value is added to generated Pulse instances;
 *   operators can then respond to (or ignore) this setting as appropriate.
 *   This parameter can be used in conjunction with the Encode transform in
 *   the vega-encode module.
 * @param {function} [prerun] - An optional callback function to invoke
 *   immediately before dataflow evaluation commences.
 * @param {function} [postrun] - An optional callback function to invoke
 *   after dataflow evaluation completes. The callback will be invoked
 *   after those registered via {@link runAfter}.
 * @return {Dataflow} - This dataflow instance.
 */
function run(encode, prerun, postrun) {
  return this._pulse ? reentrant(this)
    : (this.evaluate(encode, prerun, postrun), this);
}

/**
 * Schedules a callback function to be invoked after the current pulse
 * propagation completes. If no propagation is currently occurring,
 * the function is invoked immediately. Callbacks scheduled via runAfter
 * are invoked immediately upon completion of the current cycle, before
 * any request queued via runAsync. This method is primarily intended for
 * internal use. Third-party callers using runAfter to schedule a callback
 * that invokes {@link run} or {@link runAsync} should not use this method,
 * but instead use {@link runAsync} with prerun or postrun arguments.
 * @param {function(Dataflow)} callback - The callback function to run.
 *   The callback will be invoked with this Dataflow instance as its
 *   sole argument.
 * @param {boolean} enqueue - A boolean flag indicating that the
 *   callback should be queued up to run after the next propagation
 *   cycle, suppressing immediate invocation when propagation is not
 *   currently occurring.
 * @param {number} [priority] - A priority value used to sort registered
 *   callbacks to determine execution order. This argument is intended
 *   for internal Vega use only.
 */
function runAfter(callback, enqueue, priority) {
  if (this._pulse || enqueue) {
    // pulse propagation is currently running, queue to run after
    this._postrun.push({
      priority: priority || 0,
      callback: callback
    });
  } else {
    // pulse propagation already complete, invoke immediately
    try { callback(this); } catch (err) { this.error(err); }
  }
}

/**
 * Raise an error for re-entrant dataflow evaluation.
 */
function reentrant(df) {
  df.error('Dataflow already running. Use runAsync() to chain invocations.');
  return df;
}

/**
 * Enqueue an operator into the priority queue for evaluation. The operator
 * will be enqueued if it has no registered pulse for the current cycle, or if
 * the force argument is true. Upon enqueue, this method also sets the
 * operator's qrank to the current rank value.
 * @param {Operator} op - The operator to enqueue.
 * @param {boolean} [force] - A flag indicating if the operator should be
 *   forceably added to the queue, even if it has already been previously
 *   enqueued during the current pulse propagation. This is useful when the
 *   dataflow graph is dynamically modified and the operator rank changes.
 */
function enqueue(op, force) {
  var q = op.stamp < this._clock;
  if (q) op.stamp = this._clock;
  if (q || force) {
    op.qrank = op.rank;
    this._heap.push(op);
  }
}

/**
 * Provide a correct pulse for evaluating an operator. If the operator has an
 * explicit source operator, we will try to pull the pulse(s) from it.
 * If there is an array of source operators, we build a multi-pulse.
 * Otherwise, we return a current pulse with correct source data.
 * If the pulse is the pulse map has an explicit target set, we use that.
 * Else if the pulse on the upstream source operator is current, we use that.
 * Else we use the pulse from the pulse map, but copy the source tuple array.
 * @param {Operator} op - The operator for which to get an input pulse.
 * @param {string} [encode] - An (optional) encoding set name with which to
 *   annotate the returned pulse. See {@link run} for more information.
 */
function getPulse(op, encode) {
  var s = op.source,
      stamp = this._clock;

  return s && isArray(s)
    ? new MultiPulse(this, stamp, s.map(_ => _.pulse), encode)
    : this._input[op.id] || singlePulse(this._pulse, s && s.pulse);
}

function singlePulse(p, s) {
  if (s && s.stamp === p.stamp) {
    return s;
  }

  p = p.fork();
  if (s && s !== StopPropagation) {
    p.source = s.source;
  }
  return p;
}

var NO_OPT = {skip: false, force: false};

/**
 * Touches an operator, scheduling it to be evaluated. If invoked outside of
 * a pulse propagation, the operator will be evaluated the next time this
 * dataflow is run. If invoked in the midst of pulse propagation, the operator
 * will be queued for evaluation if and only if the operator has not yet been
 * evaluated on the current propagation timestamp.
 * @param {Operator} op - The operator to touch.
 * @param {object} [options] - Additional options hash.
 * @param {boolean} [options.skip] - If true, the operator will
 *   be skipped: it will not be evaluated, but its dependents will be.
 * @return {Dataflow}
 */
function touch(op, options) {
  var opt = options || NO_OPT;
  if (this._pulse) {
    // if in midst of propagation, add to priority queue
    this._enqueue(op);
  } else {
    // otherwise, queue for next propagation
    this._touched.add(op);
  }
  if (opt.skip) op.skip(true);
  return this;
}

/**
 * Updates the value of the given operator.
 * @param {Operator} op - The operator to update.
 * @param {*} value - The value to set.
 * @param {object} [options] - Additional options hash.
 * @param {boolean} [options.force] - If true, the operator will
 *   be re-evaluated even if its value has not changed.
 * @param {boolean} [options.skip] - If true, the operator will
 *   be skipped: it will not be evaluated, but its dependents will be.
 * @return {Dataflow}
 */
function update(op, value, options) {
  var opt = options || NO_OPT;
  if (op.set(value) || opt.force) {
    this.touch(op, opt);
  }
  return this;
}

/**
 * Pulses an operator with a changeset of tuples. If invoked outside of
 * a pulse propagation, the pulse will be applied the next time this
 * dataflow is run. If invoked in the midst of pulse propagation, the pulse
 * will be added to the set of active pulses and will be applied if and
 * only if the target operator has not yet been evaluated on the current
 * propagation timestamp.
 * @param {Operator} op - The operator to pulse.
 * @param {ChangeSet} value - The tuple changeset to apply.
 * @param {object} [options] - Additional options hash.
 * @param {boolean} [options.skip] - If true, the operator will
 *   be skipped: it will not be evaluated, but its dependents will be.
 * @return {Dataflow}
 */
function pulse(op, changeset, options) {
  this.touch(op, options || NO_OPT);

  var p = new Pulse(this, this._clock + (this._pulse ? 0 : 1)),
      t = op.pulse && op.pulse.source || [];

  p.target = op;
  this._input[op.id] = changeset.pulse(p, t);

  return this;
}

function Heap(cmp) {
  var nodes = [];
  return {
    clear: () => nodes = [],
    size: () => nodes.length,
    peek: () => nodes[0],
    push: x => {
      nodes.push(x);
      return siftdown(nodes, 0, nodes.length - 1, cmp);
    },
    pop: () => {
      var last = nodes.pop(), item;
      if (nodes.length) {
        item = nodes[0];
        nodes[0] = last;
        siftup(nodes, 0, cmp);
      } else {
        item = last;
      }
      return item;
    }
  };
}

function siftdown(array, start, idx, cmp) {
  var item, parent, pidx;

  item = array[idx];
  while (idx > start) {
    pidx = (idx - 1) >> 1;
    parent = array[pidx];
    if (cmp(item, parent) < 0) {
      array[idx] = parent;
      idx = pidx;
      continue;
    }
    break;
  }
  return (array[idx] = item);
}

function siftup(array, idx, cmp) {
  var start = idx,
      end = array.length,
      item = array[idx],
      cidx = (idx << 1) + 1, ridx;

  while (cidx < end) {
    ridx = cidx + 1;
    if (ridx < end && cmp(array[cidx], array[ridx]) >= 0) {
      cidx = ridx;
    }
    array[idx] = array[cidx];
    idx = cidx;
    cidx = (idx << 1) + 1;
  }
  array[idx] = item;
  return siftdown(array, start, idx, cmp);
}

/**
 * A dataflow graph for reactive processing of data streams.
 * @constructor
 */
function Dataflow() {
  this.logger(logger());
  this.logLevel(Error$1);

  this._clock = 0;
  this._rank = 0;
  try {
    this._loader = loader();
  } catch (e) {
    // do nothing if loader module is unavailable
  }

  this._touched = UniqueList(id);
  this._input = {};
  this._pulse = null;

  this._heap = Heap((a, b) => a.qrank - b.qrank);
  this._postrun = [];
}

var prototype$5 = Dataflow.prototype;

/**
 * The current timestamp of this dataflow. This value reflects the
 * timestamp of the previous dataflow run. The dataflow is initialized
 * with a stamp value of 0. The initial run of the dataflow will have
 * a timestap of 1, and so on. This value will match the
 * {@link Pulse.stamp} property.
 * @return {number} - The current timestamp value.
 */
prototype$5.stamp = function() {
  return this._clock;
};

/**
 * Gets or sets the loader instance to use for data file loading. A
 * loader object must provide a "load" method for loading files and a
 * "sanitize" method for checking URL/filename validity. Both methods
 * should accept a URI and options hash as arguments, and return a Promise
 * that resolves to the loaded file contents (load) or a hash containing
 * sanitized URI data with the sanitized url assigned to the "href" property
 * (sanitize).
 * @param {object} _ - The loader instance to use.
 * @return {object|Dataflow} - If no arguments are provided, returns
 *   the current loader instance. Otherwise returns this Dataflow instance.
 */
prototype$5.loader = function(_) {
  if (arguments.length) {
    this._loader = _;
    return this;
  } else {
    return this._loader;
  }
};

/**
 * Empty entry threshold for garbage cleaning. Map data structures will
 * perform cleaning once the number of empty entries exceeds this value.
 */
prototype$5.cleanThreshold = 1e4;

// OPERATOR REGISTRATION
prototype$5.add = add;
prototype$5.connect = connect;
prototype$5.rank = rank;
prototype$5.rerank = rerank;

// OPERATOR UPDATES
prototype$5.pulse = pulse;
prototype$5.touch = touch;
prototype$5.update = update;
prototype$5.changeset = changeset;

// DATA LOADING
prototype$5.ingest = ingest$1;
prototype$5.parse  = parse$1;
prototype$5.preload = preload;
prototype$5.request = request;

// EVENT HANDLING
prototype$5.events = events;
prototype$5.on = on;

// PULSE PROPAGATION
prototype$5.evaluate = evaluate;
prototype$5.run = run;
prototype$5.runAsync = runAsync;
prototype$5.runAfter = runAfter;
prototype$5._enqueue = enqueue;
prototype$5._getPulse = getPulse;

// LOGGING AND ERROR HANDLING

function logMethod(method) {
  return function() {
    return this._log[method].apply(this, arguments);
  };
}

/**
 * Get or set the logger instance used to log messages. If no arguments are
 * provided, returns the current logger instance. Otherwise, sets the logger
 * and return this Dataflow instance. Provided loggers must support the full
 * API of logger objects generated by the vega-util logger method. Note that
 * by default the log level of the new logger will be used; use the logLevel
 * method to adjust the log level as needed.
 */
prototype$5.logger = function(logger) {
  if (arguments.length) {
    this._log = logger;
    return this;
  } else {
    return this._log;
  }
};

/**
 * Logs an error message. By default, logged messages are written to console
 * output. The message will only be logged if the current log level is high
 * enough to permit error messages.
 */
prototype$5.error = logMethod('error');

/**
 * Logs a warning message. By default, logged messages are written to console
 * output. The message will only be logged if the current log level is high
 * enough to permit warning messages.
 */
prototype$5.warn = logMethod('warn');

/**
 * Logs a information message. By default, logged messages are written to
 * console output. The message will only be logged if the current log level is
 * high enough to permit information messages.
 */
prototype$5.info = logMethod('info');

/**
 * Logs a debug message. By default, logged messages are written to console
 * output. The message will only be logged if the current log level is high
 * enough to permit debug messages.
 */
prototype$5.debug = logMethod('debug');

/**
 * Get or set the current log level. If an argument is provided, it
 * will be used as the new log level.
 * @param {number} [level] - Should be one of None, Warn, Info
 * @return {number} - The current log level.
 */
prototype$5.logLevel = logMethod('level');

/**
 * Abstract class for operators that process data tuples.
 * Subclasses must provide a {@link transform} method for operator processing.
 * @constructor
 * @param {*} [init] - The initial value for this operator.
 * @param {object} [params] - The parameters for this operator.
 * @param {Operator} [source] - The operator from which to receive pulses.
 */
function Transform(init, params) {
  Operator.call(this, init, null, params);
}

var prototype$6 = inherits(Transform, Operator);

/**
 * Overrides {@link Operator.evaluate} for transform operators.
 * Internally, this method calls {@link evaluate} to perform processing.
 * If {@link evaluate} returns a falsy value, the input pulse is returned.
 * This method should NOT be overridden, instead overrride {@link evaluate}.
 * @param {Pulse} pulse - the current dataflow pulse.
 * @return the output pulse for this operator (or StopPropagation)
 */
prototype$6.run = function(pulse) {
  if (pulse.stamp < this.stamp) return pulse.StopPropagation;

  var rv;
  if (this.skip()) {
    this.skip(false);
  } else {
    rv = this.evaluate(pulse);
  }
  rv = rv || pulse;

  if (rv.then) {
    rv = rv.then(_ => this.pulse =_);
  } else if (rv !== pulse.StopPropagation) {
    this.pulse = rv;
  }

  return rv;
};

/**
 * Overrides {@link Operator.evaluate} for transform operators.
 * Marshalls parameter values and then invokes {@link transform}.
 * @param {Pulse} pulse - the current dataflow pulse.
 * @return {Pulse} The output pulse (or StopPropagation). A falsy return
     value (including undefined) will let the input pulse pass through.
 */
prototype$6.evaluate = function(pulse) {
  var params = this.marshall(pulse.stamp),
      out = this.transform(params, pulse);
  params.clear();
  return out;
};

/**
 * Process incoming pulses.
 * Subclasses should override this method to implement transforms.
 * @param {Parameters} _ - The operator parameter values.
 * @param {Pulse} pulse - The current dataflow pulse.
 * @return {Pulse} The output pulse (or StopPropagation). A falsy return
 *   value (including undefined) will let the input pulse pass through.
 */
prototype$6.transform = function() {};

var transforms = {};

function definition(type) {
  var t = transform(type);
  return t && t.Definition || null;
}

function transform(type) {
  type = type && type.toLowerCase();
  return hasOwnProperty(transforms, type) ? transforms[type] : null;
}

function multikey(f) {
  return function(x) {
    var n = f.length,
        i = 1,
        k = String(f[0](x));

    for (; i<n; ++i) {
      k += '|' + f[i](x);
    }

    return k;
  };
}

function groupkey(fields) {
  return !fields || !fields.length ? function() { return ''; }
    : fields.length === 1 ? fields[0]
    : multikey(fields);
}

function measureName(op, field, as) {
  return as || (op + (!field ? '' : '_' + field));
}

var AggregateOps = {
  'values': measure({
    name: 'values',
    init: 'cell.store = true;',
    set:  'cell.data.values()', idx: -1
  }),
  'count': measure({
    name: 'count',
    set:  'cell.num'
  }),
  '__count__': measure({
    name: 'count',
    set:  'this.missing + this.valid'
  }),
  'missing': measure({
    name: 'missing',
    set:  'this.missing'
  }),
  'valid': measure({
    name: 'valid',
    set:  'this.valid'
  }),
  'sum': measure({
    name: 'sum',
    init: 'this.sum = 0;',
    add:  'this.sum += +v;',
    rem:  'this.sum -= v;',
    set:  'this.sum'
  }),
  'mean': measure({
    name: 'mean',
    init: 'this.mean = 0;',
    add:  'var d = v - this.mean; this.mean += d / this.valid;',
    rem:  'var d = v - this.mean; this.mean -= this.valid ? d / this.valid : this.mean;',
    set:  'this.valid ? this.mean : undefined'
  }),
  'average': measure({
    name: 'average',
    set:  'this.valid ? this.mean : undefined',
    req:  ['mean'], idx: 1
  }),
  'variance': measure({
    name: 'variance',
    init: 'this.dev = 0;',
    add:  'this.dev += d * (v - this.mean);',
    rem:  'this.dev -= d * (v - this.mean);',
    set:  'this.valid > 1 ? this.dev / (this.valid-1) : undefined',
    req:  ['mean'], idx: 1
  }),
  'variancep': measure({
    name: 'variancep',
    set:  'this.valid > 1 ? this.dev / this.valid : undefined',
    req:  ['variance'], idx: 2
  }),
  'stdev': measure({
    name: 'stdev',
    set:  'this.valid > 1 ? Math.sqrt(this.dev / (this.valid-1)) : undefined',
    req:  ['variance'], idx: 2
  }),
  'stdevp': measure({
    name: 'stdevp',
    set:  'this.valid > 1 ? Math.sqrt(this.dev / this.valid) : undefined',
    req:  ['variance'], idx: 2
  }),
  'stderr': measure({
    name: 'stderr',
    set:  'this.valid > 1 ? Math.sqrt(this.dev / (this.valid * (this.valid-1))) : undefined',
    req:  ['variance'], idx: 2
  }),
  'distinct': measure({
    name: 'distinct',
    set:  'cell.data.distinct(this.get)',
    req:  ['values'], idx: 3
  }),
  'ci0': measure({
    name: 'ci0',
    set:  'cell.data.ci0(this.get)',
    req:  ['values'], idx: 3
  }),
  'ci1': measure({
    name: 'ci1',
    set:  'cell.data.ci1(this.get)',
    req:  ['values'], idx: 3
  }),
  'median': measure({
    name: 'median',
    set:  'cell.data.q2(this.get)',
    req:  ['values'], idx: 3
  }),
  'q1': measure({
    name: 'q1',
    set:  'cell.data.q1(this.get)',
    req:  ['values'], idx: 3
  }),
  'q3': measure({
    name: 'q3',
    set:  'cell.data.q3(this.get)',
    req:  ['values'], idx: 3
  }),
  'argmin': measure({
    name: 'argmin',
    init: 'this.argmin = undefined;',
    add:  'if (v < this.min) this.argmin = t;',
    rem:  'if (v <= this.min) this.argmin = undefined;',
    set:  'this.argmin || cell.data.argmin(this.get)',
    req:  ['min'], str: ['values'], idx: 3
  }),
  'argmax': measure({
    name: 'argmax',
    init: 'this.argmax = undefined;',
    add:  'if (v > this.max) this.argmax = t;',
    rem:  'if (v >= this.max) this.argmax = undefined;',
    set:  'this.argmax || cell.data.argmax(this.get)',
    req:  ['max'], str: ['values'], idx: 3
  }),
  'min': measure({
    name: 'min',
    init: 'this.min = undefined;',
    add:  'if (v < this.min || this.min === undefined) this.min = v;',
    rem:  'if (v <= this.min) this.min = NaN;',
    set:  'this.min = (Number.isNaN(this.min) ? cell.data.min(this.get) : this.min)',
    str:  ['values'], idx: 4
  }),
  'max': measure({
    name: 'max',
    init: 'this.max = undefined;',
    add:  'if (v > this.max || this.max === undefined) this.max = v;',
    rem:  'if (v >= this.max) this.max = NaN;',
    set:  'this.max = (Number.isNaN(this.max) ? cell.data.max(this.get) : this.max)',
    str:  ['values'], idx: 4
  })
};

var ValidAggregateOps = Object.keys(AggregateOps);

function createMeasure(op, name) {
  return AggregateOps[op](name);
}

function measure(base) {
  return function(out) {
    var m = extend({init:'', add:'', rem:'', idx:0}, base);
    m.out = out || base.name;
    return m;
  };
}

function compareIndex(a, b) {
  return a.idx - b.idx;
}

function resolve(agg, stream) {
  function collect(m, a) {
    function helper(r) { if (!m[r]) collect(m, m[r] = AggregateOps[r]()); }
    if (a.req) a.req.forEach(helper);
    if (stream && a.str) a.str.forEach(helper);
    return m;
  }
  var map = agg.reduce(
    collect,
    agg.reduce(function(m, a) {
      m[a.name] = a;
      return m;
    }, {})
  );
  var values = [], key;
  for (key in map) values.push(map[key]);
  return values.sort(compareIndex);
}

function compileMeasures(agg, field) {
  var get = field || identity,
      all = resolve(agg, true), // assume streaming removes may occur
      init = 'var cell = this.cell; this.valid = 0; this.missing = 0;',
      ctr = 'this.cell = cell; this.init();',
      add = 'if(v==null){++this.missing; return;} if(v!==v) return; ++this.valid;',
      rem = 'if(v==null){--this.missing; return;} if(v!==v) return; --this.valid;',
      set = 'var cell = this.cell;';

  all.forEach(function(a) {
    init += a.init;
    add += a.add;
    rem += a.rem;
  });
  agg.slice().sort(compareIndex).forEach(function(a) {
    set += 't[' + $(a.out) + ']=' + a.set + ';';
  });
  set += 'return t;';

  ctr = Function('cell', ctr);
  ctr.prototype.init = Function(init);
  ctr.prototype.add = Function('v', 't', add);
  ctr.prototype.rem = Function('v', 't', rem);
  ctr.prototype.set = Function('t', set);
  ctr.prototype.get = get;
  ctr.fields = agg.map(function(_) { return _.out; });
  return ctr;
}

function* numbers(values, valueof) {
  if (valueof === undefined) {
    for (let value of values) {
      if (value != null && (value = +value) >= value) {
        yield value;
      }
    }
  } else {
    let index = -1;
    for (let value of values) {
      if ((value = valueof(value, ++index, values)) != null && (value = +value) >= value) {
        yield value;
      }
    }
  }
}

function ascending(a, b) {
  return a < b ? -1 : a > b ? 1 : a >= b ? 0 : NaN;
}

function bisector(compare) {
  if (compare.length === 1) compare = ascendingComparator(compare);
  return {
    left: function(a, x, lo, hi) {
      if (lo == null) lo = 0;
      if (hi == null) hi = a.length;
      while (lo < hi) {
        var mid = lo + hi >>> 1;
        if (compare(a[mid], x) < 0) lo = mid + 1;
        else hi = mid;
      }
      return lo;
    },
    right: function(a, x, lo, hi) {
      if (lo == null) lo = 0;
      if (hi == null) hi = a.length;
      while (lo < hi) {
        var mid = lo + hi >>> 1;
        if (compare(a[mid], x) > 0) hi = mid;
        else lo = mid + 1;
      }
      return lo;
    }
  };
}

function ascendingComparator(f) {
  return function(d, x) {
    return ascending(f(d), x);
  };
}

var ascendingBisect = bisector(ascending);
var bisectRight = ascendingBisect.right;
var bisectLeft = ascendingBisect.left;

function variance(values, valueof) {
  let count = 0;
  let delta;
  let mean = 0;
  let sum = 0;
  if (valueof === undefined) {
    for (let value of values) {
      if (value != null && (value = +value) >= value) {
        delta = value - mean;
        mean += delta / ++count;
        sum += delta * (value - mean);
      }
    }
  } else {
    let index = -1;
    for (let value of values) {
      if ((value = valueof(value, ++index, values)) != null && (value = +value) >= value) {
        delta = value - mean;
        mean += delta / ++count;
        sum += delta * (value - mean);
      }
    }
  }
  if (count > 1) return sum / (count - 1);
}

function deviation(values, valueof) {
  const v = variance(values, valueof);
  return v ? Math.sqrt(v) : v;
}

function sequence(start, stop, step) {
  start = +start, stop = +stop, step = (n = arguments.length) < 2 ? (stop = start, start = 0, 1) : n < 3 ? 1 : +step;

  var i = -1,
      n = Math.max(0, Math.ceil((stop - start) / step)) | 0,
      range = new Array(n);

  while (++i < n) {
    range[i] = start + i * step;
  }

  return range;
}

var e10 = Math.sqrt(50),
    e5 = Math.sqrt(10),
    e2 = Math.sqrt(2);

function ticks(start, stop, count) {
  var reverse,
      i = -1,
      n,
      ticks,
      step;

  stop = +stop, start = +start, count = +count;
  if (start === stop && count > 0) return [start];
  if (reverse = stop < start) n = start, start = stop, stop = n;
  if ((step = tickIncrement(start, stop, count)) === 0 || !isFinite(step)) return [];

  if (step > 0) {
    start = Math.ceil(start / step);
    stop = Math.floor(stop / step);
    ticks = new Array(n = Math.ceil(stop - start + 1));
    while (++i < n) ticks[i] = (start + i) * step;
  } else {
    start = Math.floor(start * step);
    stop = Math.ceil(stop * step);
    ticks = new Array(n = Math.ceil(start - stop + 1));
    while (++i < n) ticks[i] = (start - i) / step;
  }

  if (reverse) ticks.reverse();

  return ticks;
}

function tickIncrement(start, stop, count) {
  var step = (stop - start) / Math.max(0, count),
      power = Math.floor(Math.log(step) / Math.LN10),
      error = step / Math.pow(10, power);
  return power >= 0
      ? (error >= e10 ? 10 : error >= e5 ? 5 : error >= e2 ? 2 : 1) * Math.pow(10, power)
      : -Math.pow(10, -power) / (error >= e10 ? 10 : error >= e5 ? 5 : error >= e2 ? 2 : 1);
}

function tickStep(start, stop, count) {
  var step0 = Math.abs(stop - start) / Math.max(0, count),
      step1 = Math.pow(10, Math.floor(Math.log(step0) / Math.LN10)),
      error = step0 / step1;
  if (error >= e10) step1 *= 10;
  else if (error >= e5) step1 *= 5;
  else if (error >= e2) step1 *= 2;
  return stop < start ? -step1 : step1;
}

function max(values, valueof) {
  let max;
  if (valueof === undefined) {
    for (const value of values) {
      if (value != null
          && (max < value || (max === undefined && value >= value))) {
        max = value;
      }
    }
  } else {
    let index = -1;
    for (let value of values) {
      if ((value = valueof(value, ++index, values)) != null
          && (max < value || (max === undefined && value >= value))) {
        max = value;
      }
    }
  }
  return max;
}

function min(values, valueof) {
  let min;
  if (valueof === undefined) {
    for (const value of values) {
      if (value != null
          && (min > value || (min === undefined && value >= value))) {
        min = value;
      }
    }
  } else {
    let index = -1;
    for (let value of values) {
      if ((value = valueof(value, ++index, values)) != null
          && (min > value || (min === undefined && value >= value))) {
        min = value;
      }
    }
  }
  return min;
}

// Based on https://github.com/mourner/quickselect
// ISC license, Copyright 2018 Vladimir Agafonkin.
function quickselect(array, k, left = 0, right = array.length - 1, compare = ascending) {
  while (right > left) {
    if (right - left > 600) {
      const n = right - left + 1;
      const m = k - left + 1;
      const z = Math.log(n);
      const s = 0.5 * Math.exp(2 * z / 3);
      const sd = 0.5 * Math.sqrt(z * s * (n - s) / n) * (m - n / 2 < 0 ? -1 : 1);
      const newLeft = Math.max(left, Math.floor(k - m * s / n + sd));
      const newRight = Math.min(right, Math.floor(k + (n - m) * s / n + sd));
      quickselect(array, k, newLeft, newRight, compare);
    }

    const t = array[k];
    let i = left;
    let j = right;

    swap(array, left, k);
    if (compare(array[right], t) > 0) swap(array, left, right);

    while (i < j) {
      swap(array, i, j), ++i, --j;
      while (compare(array[i], t) < 0) ++i;
      while (compare(array[j], t) > 0) --j;
    }

    if (compare(array[left], t) === 0) swap(array, left, j);
    else ++j, swap(array, j, right);

    if (j <= k) left = j + 1;
    if (k <= j) right = j - 1;
  }
  return array;
}

function swap(array, i, j) {
  const t = array[i];
  array[i] = array[j];
  array[j] = t;
}

function number(x) {
  return x === null ? NaN : +x;
}

function* numbers$1(values, valueof) {
  if (valueof === undefined) {
    for (let value of values) {
      if (value != null && (value = +value) >= value) {
        yield value;
      }
    }
  } else {
    let index = -1;
    for (let value of values) {
      if ((value = valueof(value, ++index, values)) != null && (value = +value) >= value) {
        yield value;
      }
    }
  }
}

function quantile(values, p, valueof) {
  values = Float64Array.from(numbers$1(values, valueof));
  if (!(n = values.length)) return;
  if ((p = +p) <= 0 || n < 2) return min(values);
  if (p >= 1) return max(values);
  var n,
      i = (n - 1) * p,
      i0 = Math.floor(i),
      value0 = max(quickselect(values, i0).subarray(0, i0 + 1)),
      value1 = min(values.subarray(i0 + 1));
  return value0 + (value1 - value0) * (i - i0);
}

function quantileSorted(values, p, valueof = number) {
  if (!(n = values.length)) return;
  if ((p = +p) <= 0 || n < 2) return +valueof(values[0], 0, values);
  if (p >= 1) return +valueof(values[n - 1], n - 1, values);
  var n,
      i = (n - 1) * p,
      i0 = Math.floor(i),
      value0 = +valueof(values[i0], i0, values),
      value1 = +valueof(values[i0 + 1], i0 + 1, values);
  return value0 + (value1 - value0) * (i - i0);
}

function mean(values, valueof) {
  let count = 0;
  let sum = 0;
  if (valueof === undefined) {
    for (let value of values) {
      if (value != null && (value = +value) >= value) {
        ++count, sum += value;
      }
    }
  } else {
    let index = -1;
    for (let value of values) {
      if ((value = valueof(value, ++index, values)) != null && (value = +value) >= value) {
        ++count, sum += value;
      }
    }
  }
  if (count) return sum / count;
}

function median(values, valueof) {
  return quantile(values, 0.5, valueof);
}

function permute(source, keys) {
  return Array.from(keys, key => source[key]);
}

function sum(values, valueof) {
  let sum = 0;
  if (valueof === undefined) {
    for (let value of values) {
      if (value = +value) {
        sum += value;
      }
    }
  } else {
    let index = -1;
    for (let value of values) {
      if (value = +valueof(value, ++index, values)) {
        sum += value;
      }
    }
  }
  return sum;
}

function quantiles(array, p, f) {
  var values = Float64Array.from(numbers(array, f));

  // don't depend on return value from typed array sort call
  // protects against undefined sort results in Safari (vega/vega-lite#4964)
  values.sort(ascending);

  return p.map(_ => quantileSorted(values, _));
}

function quartiles(array, f) {
  return quantiles(array, [0.25, 0.50, 0.75], f);
}

// Scott, D. W. (1992) Multivariate Density Estimation:
// Theory, Practice, and Visualization. Wiley.
function bandwidthNRD(array, f) {
  var n = array.length,
      v = deviation(array, f),
      q = quartiles(array, f),
      h = (q[2] - q[0]) / 1.34;

  v = Math.min(v, h) || v || Math.abs(q[0]) || 1;

  return 1.06 * v * Math.pow(n, -0.2);
}

function bin(_) {
  // determine range
  var maxb = _.maxbins || 20,
      base = _.base || 10,
      logb = Math.log(base),
      div  = _.divide || [5, 2],
      min  = _.extent[0],
      max  = _.extent[1],
      span = _.span || (max - min) || Math.abs(min) || 1,
      step, level, minstep, precision, v, i, n, eps;

  if (_.step) {
    // if step size is explicitly given, use that
    step = _.step;
  } else if (_.steps) {
    // if provided, limit choice to acceptable step sizes
    v = span / maxb;
    for (i=0, n=_.steps.length; i < n && _.steps[i] < v; ++i);
    step = _.steps[Math.max(0, i-1)];
  } else {
    // else use span to determine step size
    level = Math.ceil(Math.log(maxb) / logb);
    minstep = _.minstep || 0;
    step = Math.max(
      minstep,
      Math.pow(base, Math.round(Math.log(span) / logb) - level)
    );

    // increase step size if too many bins
    while (Math.ceil(span/step) > maxb) { step *= base; }

    // decrease step size if allowed
    for (i=0, n=div.length; i<n; ++i) {
      v = step / div[i];
      if (v >= minstep && span / v <= maxb) step = v;
    }
  }

  // update precision, min and max
  v = Math.log(step);
  precision = v >= 0 ? 0 : ~~(-v / logb) + 1;
  eps = Math.pow(base, -precision - 1);
  if (_.nice || _.nice === undefined) {
    v = Math.floor(min / step + eps) * step;
    min = min < v ? v - step : v;
    max = Math.ceil(max / step) * step;
  }

  return {
    start: min,
    stop:  max === min ? min + step : max,
    step:  step
  };
}

var random = Math.random;

function setRandom(r) {
  random = r;
}

function bootstrapCI(array, samples, alpha, f) {
  if (!array.length) return [undefined, undefined];

  var values = Float64Array.from(numbers(array, f)),
      n = values.length,
      m = samples,
      a, i, j, mu;

  for (j=0, mu=Array(m); j<m; ++j) {
    for (a=0, i=0; i<n; ++i) {
      a += values[~~(random() * n)];
    }
    mu[j] = a / n;
  }

  mu.sort(ascending);

  return [
    quantile(mu, alpha/2),
    quantile(mu, 1-(alpha/2))
  ];
}

// Dot density binning for dot plot construction.
// Based on Leland Wilkinson, Dot Plots, The American Statistician, 1999.
// https://www.cs.uic.edu/~wilkinson/Publications/dotplots.pdf
function dotbin(array, step, smooth, f) {
  f = f || (_ => _);

  let i = 0, j = 1,
      n = array.length,
      v = new Float64Array(n),
      a = f(array[0]),
      b = a,
      w = a + step,
      x;

  for (; j<n; ++j) {
    x = f(array[j]);
    if (x >= w) {
      b = (a + b) / 2;
      for (; i<j; ++i) v[i] = b;
      w = x + step;
      a = x;
    }
    b = x;
  }

  b = (a + b) / 2;
  for (; i<j; ++i) v[i] = b;

  return smooth ? smoothing(v, step + step / 4) : v;
}

// perform smoothing to reduce variance
// swap points between "adjacent" stacks
// Wilkinson defines adjacent as within step/4 units
function smoothing(v, thresh) {
  let n = v.length,
      a = 0,
      b = 1,
      c, d;

  // get left stack
  while (v[a] === v[b]) ++b;

  while (b < n) {
    // get right stack
    c = b + 1;
    while (v[b] === v[c]) ++c;

    // are stacks adjacent?
    // if so, compare sizes and swap as needed
    if (v[b] - v[b-1] < thresh) {
      d = b + ((a + c - b - b) >> 1);
      while (d < b) v[d++] = v[b];
      while (d > b) v[d--] = v[a];
    }

    // update left stack indices
    a = b;
    b = c;
  }

  return v;
}

function lcg(seed) {
  // Random numbers using a Linear Congruential Generator with seed value
  // Uses glibc values from https://en.wikipedia.org/wiki/Linear_congruential_generator
  return function() {
    seed = (1103515245 * seed + 12345) % 2147483647;
    return seed / 2147483647;
  };
}

function integer(min, max) {
  if (max == null) {
    max = min;
    min = 0;
  }

  var dist = {},
      a, b, d;

  dist.min = function(_) {
    if (arguments.length) {
      a = _ || 0;
      d = b - a;
      return dist;
    } else {
      return a;
    }
  };

  dist.max = function(_) {
    if (arguments.length) {
      b = _ || 0;
      d = b - a;
      return dist;
    } else {
      return b;
    }
  };

  dist.sample = function() {
    return a + Math.floor(d * random());
  };

  dist.pdf = function(x) {
    return (x === Math.floor(x) && x >= a && x < b) ? 1 / d : 0;
  };

  dist.cdf = function(x) {
    var v = Math.floor(x);
    return v < a ? 0 : v >= b ? 1 : (v - a + 1) / d;
  };

  dist.icdf = function(p) {
    return (p >= 0 && p <= 1) ? a - 1 + Math.floor(p * d) : NaN;
  };

  return dist.min(min).max(max);
}

const SQRT2PI = Math.sqrt(2 * Math.PI);
const SQRT2 = Math.SQRT2;

let nextSample = NaN;

function sampleNormal(mean, stdev) {
  mean = mean || 0;
  stdev = stdev == null ? 1 : stdev;

  let x = 0, y = 0, rds, c;
  if (nextSample === nextSample) {
    x = nextSample;
    nextSample = NaN;
  } else {
    do {
      x = random() * 2 - 1;
      y = random() * 2 - 1;
      rds = x * x + y * y;
    } while (rds === 0 || rds > 1);
    c = Math.sqrt(-2 * Math.log(rds) / rds); // Box-Muller transform
    x *= c;
    nextSample = y * c;
  }
  return mean + x * stdev;
}

function densityNormal(value, mean, stdev) {
  stdev = stdev == null ? 1 : stdev;
  const z = (value - (mean || 0)) / stdev;
  return Math.exp(-0.5 * z * z) / (stdev * SQRT2PI);
}

// Approximation from West (2009)
// Better Approximations to Cumulative Normal Functions
function cumulativeNormal(value, mean, stdev) {
  mean = mean || 0;
  stdev = stdev == null ? 1 : stdev;

  let cd,
      z = (value - mean) / stdev,
      Z = Math.abs(z);

  if (Z > 37) {
    cd = 0;
  } else {
    let sum, exp = Math.exp(-Z * Z / 2);
    if (Z < 7.07106781186547) {
      sum = 3.52624965998911e-02 * Z + 0.700383064443688;
      sum = sum * Z + 6.37396220353165;
      sum = sum * Z + 33.912866078383;
      sum = sum * Z + 112.079291497871;
      sum = sum * Z + 221.213596169931;
      sum = sum * Z + 220.206867912376;
      cd = exp * sum;
      sum = 8.83883476483184e-02 * Z + 1.75566716318264;
      sum = sum * Z + 16.064177579207;
      sum = sum * Z + 86.7807322029461;
      sum = sum * Z + 296.564248779674;
      sum = sum * Z + 637.333633378831;
      sum = sum * Z + 793.826512519948;
      sum = sum * Z + 440.413735824752;
      cd = cd / sum;
    } else {
      sum = Z + 0.65;
      sum = Z + 4 / sum;
      sum = Z + 3 / sum;
      sum = Z + 2 / sum;
      sum = Z + 1 / sum;
      cd = exp / sum / 2.506628274631;
    }
  }
  return z > 0 ? 1 - cd : cd;
}

// Approximation of Probit function using inverse error function.
function quantileNormal(p, mean, stdev) {
  if (p < 0 || p > 1) return NaN;
  return (mean || 0) + (stdev == null ? 1 : stdev) * SQRT2 * erfinv(2 * p - 1);
}

// Approximate inverse error function. Implementation from "Approximating
// the erfinv function" by Mike Giles, GPU Computing Gems, volume 2, 2010.
// Ported from Apache Commons Math, http://www.apache.org/licenses/LICENSE-2.0
function erfinv(x) {
  // beware that the logarithm argument must be
  // commputed as (1.0 - x) * (1.0 + x),
  // it must NOT be simplified as 1.0 - x * x as this
  // would induce rounding errors near the boundaries +/-1
  let w = - Math.log((1 - x) * (1 + x)), p;

  if (w < 6.25) {
      w -= 3.125;
      p =  -3.6444120640178196996e-21;
      p =   -1.685059138182016589e-19 + p * w;
      p =   1.2858480715256400167e-18 + p * w;
      p =    1.115787767802518096e-17 + p * w;
      p =   -1.333171662854620906e-16 + p * w;
      p =   2.0972767875968561637e-17 + p * w;
      p =   6.6376381343583238325e-15 + p * w;
      p =  -4.0545662729752068639e-14 + p * w;
      p =  -8.1519341976054721522e-14 + p * w;
      p =   2.6335093153082322977e-12 + p * w;
      p =  -1.2975133253453532498e-11 + p * w;
      p =  -5.4154120542946279317e-11 + p * w;
      p =    1.051212273321532285e-09 + p * w;
      p =  -4.1126339803469836976e-09 + p * w;
      p =  -2.9070369957882005086e-08 + p * w;
      p =   4.2347877827932403518e-07 + p * w;
      p =  -1.3654692000834678645e-06 + p * w;
      p =  -1.3882523362786468719e-05 + p * w;
      p =    0.0001867342080340571352 + p * w;
      p =  -0.00074070253416626697512 + p * w;
      p =   -0.0060336708714301490533 + p * w;
      p =      0.24015818242558961693 + p * w;
      p =       1.6536545626831027356 + p * w;
  } else if (w < 16.0) {
      w = Math.sqrt(w) - 3.25;
      p =   2.2137376921775787049e-09;
      p =   9.0756561938885390979e-08 + p * w;
      p =  -2.7517406297064545428e-07 + p * w;
      p =   1.8239629214389227755e-08 + p * w;
      p =   1.5027403968909827627e-06 + p * w;
      p =   -4.013867526981545969e-06 + p * w;
      p =   2.9234449089955446044e-06 + p * w;
      p =   1.2475304481671778723e-05 + p * w;
      p =  -4.7318229009055733981e-05 + p * w;
      p =   6.8284851459573175448e-05 + p * w;
      p =   2.4031110387097893999e-05 + p * w;
      p =   -0.0003550375203628474796 + p * w;
      p =   0.00095328937973738049703 + p * w;
      p =   -0.0016882755560235047313 + p * w;
      p =    0.0024914420961078508066 + p * w;
      p =   -0.0037512085075692412107 + p * w;
      p =     0.005370914553590063617 + p * w;
      p =       1.0052589676941592334 + p * w;
      p =       3.0838856104922207635 + p * w;
  } else if (Number.isFinite(w)) {
      w = Math.sqrt(w) - 5.0;
      p =  -2.7109920616438573243e-11;
      p =  -2.5556418169965252055e-10 + p * w;
      p =   1.5076572693500548083e-09 + p * w;
      p =  -3.7894654401267369937e-09 + p * w;
      p =   7.6157012080783393804e-09 + p * w;
      p =  -1.4960026627149240478e-08 + p * w;
      p =   2.9147953450901080826e-08 + p * w;
      p =  -6.7711997758452339498e-08 + p * w;
      p =   2.2900482228026654717e-07 + p * w;
      p =  -9.9298272942317002539e-07 + p * w;
      p =   4.5260625972231537039e-06 + p * w;
      p =  -1.9681778105531670567e-05 + p * w;
      p =   7.5995277030017761139e-05 + p * w;
      p =  -0.00021503011930044477347 + p * w;
      p =  -0.00013871931833623122026 + p * w;
      p =       1.0103004648645343977 + p * w;
      p =       4.8499064014085844221 + p * w;
  } else {
      p = Infinity;
  }

  return p * x;
}

function randomNormal(mean, stdev) {
  var mu,
      sigma,
      dist = {
        mean: function(_) {
          if (arguments.length) {
            mu = _ || 0;
            return dist;
          } else {
            return mu;
          }
        },
        stdev: function(_) {
          if (arguments.length) {
            sigma = _ == null ? 1 : _;
            return dist;
          } else {
            return sigma;
          }
        },
        sample: () => sampleNormal(mu, sigma),
        pdf: value => densityNormal(value, mu, sigma),
        cdf: value => cumulativeNormal(value, mu, sigma),
        icdf: p => quantileNormal(p, mu, sigma)
      };

  return dist.mean(mean).stdev(stdev);
}

// TODO: support for additional kernels?
function randomKDE(support, bandwidth) {
  var kernel = randomNormal(),
      dist = {},
      n = 0;

  dist.data = function(_) {
    if (arguments.length) {
      support = _;
      n = _ ? _.length : 0;
      return dist.bandwidth(bandwidth);
    } else {
      return support;
    }
  };

  dist.bandwidth = function(_) {
    if (!arguments.length) return bandwidth;
    bandwidth = _;
    if (!bandwidth && support) bandwidth = bandwidthNRD(support);
    return dist;
  };

  dist.sample = function() {
    return support[~~(random() * n)] + bandwidth * kernel.sample();
  };

  dist.pdf = function(x) {
    for (var y=0, i=0; i<n; ++i) {
      y += kernel.pdf((x - support[i]) / bandwidth);
    }
    return y / bandwidth / n;
  };

  dist.cdf = function(x) {
    for (var y=0, i=0; i<n; ++i) {
      y += kernel.cdf((x - support[i]) / bandwidth);
    }
    return y / n;
  };

  dist.icdf = function() {
    throw Error('KDE icdf not supported.');
  };

  return dist.data(support);
}

function sampleLogNormal(mean, stdev) {
  mean = mean || 0;
  stdev = stdev == null ? 1 : stdev;
  return Math.exp(mean + sampleNormal() * stdev);
}

function densityLogNormal(value, mean, stdev) {
  if (value <= 0) return 0;
  mean = mean || 0;
  stdev = stdev == null ? 1 : stdev;
  const z = (Math.log(value) - mean) / stdev;
  return Math.exp(-0.5 * z * z) / (stdev * SQRT2PI * value);
}

function cumulativeLogNormal(value, mean, stdev) {
  return cumulativeNormal(Math.log(value), mean, stdev);
}

function quantileLogNormal(p, mean, stdev) {
  return Math.exp(quantileNormal(p, mean, stdev));
}

function randomLogNormal(mean, stdev) {
  var mu,
      sigma,
      dist = {
        mean: function(_) {
          if (arguments.length) {
            mu = _ || 0;
            return dist;
          } else {
            return mu;
          }
        },
        stdev: function(_) {
          if (arguments.length) {
            sigma = _ == null ? 1 : _;
            return dist;
          } else {
            return sigma;
          }
        },
        sample: () => sampleLogNormal(mu, sigma),
        pdf: value => densityLogNormal(value, mu, sigma),
        cdf: value => cumulativeLogNormal(value, mu, sigma),
        icdf: p => quantileLogNormal(p, mu, sigma)
      };

  return dist.mean(mean).stdev(stdev);
}

function randomMixture(dists, weights) {
  var dist = {}, m = 0, w;

  function normalize(x) {
    var w = [], sum = 0, i;
    for (i=0; i<m; ++i) { sum += (w[i] = (x[i]==null ? 1 : +x[i])); }
    for (i=0; i<m; ++i) { w[i] /= sum; }
    return w;
  }

  dist.weights = function(_) {
    if (arguments.length) {
      w = normalize(weights = (_ || []));
      return dist;
    }
    return weights;
  };

  dist.distributions = function(_) {
    if (arguments.length) {
      if (_) {
        m = _.length;
        dists = _;
      } else {
        m = 0;
        dists = [];
      }
      return dist.weights(weights);
    }
    return dists;
  };

  dist.sample = function() {
    var r = random(),
        d = dists[m-1],
        v = w[0],
        i = 0;

    // first select distribution
    for (; i<m-1; v += w[++i]) {
      if (r < v) { d = dists[i]; break; }
    }
    // then sample from it
    return d.sample();
  };

  dist.pdf = function(x) {
    for (var p=0, i=0; i<m; ++i) {
      p += w[i] * dists[i].pdf(x);
    }
    return p;
  };

  dist.cdf = function(x) {
    for (var p=0, i=0; i<m; ++i) {
      p += w[i] * dists[i].cdf(x);
    }
    return p;
  };

  dist.icdf = function() {
    throw Error('Mixture icdf not supported.');
  };

  return dist.distributions(dists).weights(weights);
}

function sampleUniform(min, max) {
  if (max == null) {
    max = (min == null ? 1 : min);
    min = 0;
  }
  return min + (max - min) * random();
}

function densityUniform(value, min, max) {
  if (max == null) {
    max = (min == null ? 1 : min);
    min = 0;
  }
  return (value >= min && value <= max) ? 1 / (max - min) : 0;
}

function cumulativeUniform(value, min, max) {
  if (max == null) {
    max = (min == null ? 1 : min);
    min = 0;
  }
  return value < min ? 0 : value > max ? 1 : (value - min) / (max - min);
}

function quantileUniform(p, min, max) {
  if (max == null) {
    max = (min == null ? 1 : min);
    min = 0;
  }
  return (p >= 0 && p <= 1) ? min + p * (max - min) : NaN;
}

function randomUniform(min, max) {
  var a, b,
      dist = {
        min: function(_) {
          if (arguments.length) {
            a = _ || 0;
            return dist;
          } else {
            return a;
          }
        },
        max: function(_) {
          if (arguments.length) {
            b = _ == null ? 1 : _;
            return dist;
          } else {
            return b;
          }
        },
        sample: () => sampleUniform(a, b),
        pdf: value => densityUniform(value, a, b),
        cdf: value => cumulativeUniform(value, a, b),
        icdf: p => quantileUniform(p, a, b)
      };

  if (max == null) {
    max = (min == null ? 1 : min);
    min = 0;
  }
  return dist.min(min).max(max);
}

// Ordinary Least Squares
function ols(uX, uY, uXY, uX2) {
  const delta = uX2 - uX * uX,
        slope = Math.abs(delta) < 1e-24 ? 0 : (uXY - uX * uY) / delta,
        intercept = uY - slope * uX;

  return [intercept, slope];
}

function points(data, x, y, sort) {
  data = data.filter(d => {
    let u = x(d), v = y(d);
    return u != null && (u = +u) >= u && v != null && (v = +v) >= v;
  });

  if (sort) {
    data.sort((a, b) => x(a) - x(b));
  }

  const n = data.length,
        X = new Float64Array(n),
        Y = new Float64Array(n);

  // extract values, calculate means
  let i = 0, ux = 0, uy = 0, xv, yv, d;
  for (d of data) {
    X[i] = xv = +x(d);
    Y[i] = yv = +y(d);
    ++i;
    ux += (xv - ux) / i;
    uy += (yv - uy) / i;
  }

  // mean center the data
  for (i=0; i<n; ++i) {
    X[i] -= ux;
    Y[i] -= uy;
  }

  return [X, Y, ux, uy];
}

function visitPoints(data, x, y, callback) {
  let i = -1, u, v;

  for (let d of data) {
    u = x(d);
    v = y(d);
    if (u != null && (u = +u) >= u && v != null && (v = +v) >= v) {
      callback(u, v, ++i);
    }
  }
}

// Adapted from d3-regression by Harry Stevens
// License: https://github.com/HarryStevens/d3-regression/blob/master/LICENSE
function rSquared(data, x, y, uY, predict) {
  let SSE = 0, SST = 0;

  visitPoints(data, x, y, (dx, dy) => {
    const sse = dy - predict(dx),
          sst = dy - uY;

    SSE += sse * sse;
    SST += sst * sst;
  });

  return 1 - SSE / SST;
}

// Adapted from d3-regression by Harry Stevens
// License: https://github.com/HarryStevens/d3-regression/blob/master/LICENSE
function regressionLinear(data, x, y) {
  let X = 0, Y = 0, XY = 0, X2 = 0, n = 0;

  visitPoints(data, x, y, (dx, dy) => {
    ++n;
    X += (dx - X) / n;
    Y += (dy - Y) / n;
    XY += (dx * dy - XY) / n;
    X2 += (dx * dx - X2) / n;
  });

  const coef = ols(X, Y, XY, X2),
        predict = x => coef[0] + coef[1] * x;

  return {
    coef: coef,
    predict: predict,
    rSquared: rSquared(data, x, y, Y, predict)
  };
}

// Adapted from d3-regression by Harry Stevens
// License: https://github.com/HarryStevens/d3-regression/blob/master/LICENSE
function regressionLog(data, x, y) {
  let X = 0, Y = 0, XY = 0, X2 = 0, n = 0;

  visitPoints(data, x, y, (dx, dy) => {
    ++n;
    dx = Math.log(dx);
    X += (dx - X) / n;
    Y += (dy - Y) / n;
    XY += (dx * dy - XY) / n;
    X2 += (dx * dx - X2) / n;
  });

  const coef = ols(X, Y, XY, X2),
        predict = x => coef[0] + coef[1] * Math.log(x);

  return {
    coef: coef,
    predict: predict,
    rSquared: rSquared(data, x, y, Y, predict)
  };
}

function regressionExp(data, x, y) {
  let Y = 0, YL = 0, XY = 0, XYL = 0, X2Y = 0, n = 0;

  visitPoints(data, x, y, (dx, dy) => {
    const ly = Math.log(dy),
          xy = dx * dy;
    ++n;
    Y += (dy - Y) / n;
    XY += (xy - XY) / n;
    X2Y += (dx * xy - X2Y) / n;
    YL += (dy * ly - YL) / n;
    XYL += (xy * ly - XYL) / n;
  });

  const coef = ols(XY / Y, YL / Y, XYL / Y, X2Y / Y),
        predict = x => coef[0] * Math.exp(coef[1] * x);

  coef[0] = Math.exp(coef[0]);

  return {
    coef: coef,
    predict: predict,
    rSquared: rSquared(data, x, y, Y, predict)
  };
}

// Adapted from d3-regression by Harry Stevens
// License: https://github.com/HarryStevens/d3-regression/blob/master/LICENSE
function regressionPow(data, x, y) {
  let X = 0, Y = 0, XY = 0, X2 = 0, YS = 0, n = 0;

  visitPoints(data, x, y, (dx, dy) => {
    const lx = Math.log(dx),
          ly = Math.log(dy);
    ++n;
    X += (lx - X) / n;
    Y += (ly - Y) / n;
    XY += (lx * ly - XY) / n;
    X2 += (lx * lx - X2) / n;
    YS += (dy - YS) / n;
  });

  const coef = ols(X, Y, XY, X2),
        predict = x => coef[0] * Math.pow(x, coef[1]);

  coef[0] = Math.exp(coef[0]);

  return {
    coef: coef,
    predict: predict,
    rSquared: rSquared(data, x, y, YS, predict)
  };
}

function regressionQuad(data, x, y) {

  const [xv, yv, ux, uy] = points(data, x, y),
        n = xv.length;

  let X2 = 0, X3 = 0, X4 = 0, XY = 0, X2Y = 0,
      i, dx, dy, x2;

  for (i=0; i<n;) {
    dx = xv[i];
    dy = yv[i++];
    x2 = dx * dx;
    X2 += (x2 - X2) / i;
    X3 += (x2 * dx - X3) / i;
    X4 += (x2 * x2 - X4) / i;
    XY += (dx * dy - XY) / i;
    X2Y += (x2 * dy - X2Y) / i;
  }

  const X2X2 = X4 - (X2 * X2),
        d = (X2 * X2X2 - X3 * X3),
        a = (X2Y * X2 - XY * X3) / d,
        b = (XY * X2X2 - X2Y * X3) / d,
        c = -a * X2,
        predict = x => {
          x = x - ux;
          return a * x * x + b * x + c + uy;
        };

  // transform coefficients back from mean-centered space
  return {
    coef: [
      c - b * ux + a * ux * ux + uy,
      b - 2 * a * ux,
      a
    ],
    predict: predict,
    rSquared: rSquared(data, x, y, uy, predict)
  };
}

// Adapted from d3-regression by Harry Stevens
// License: https://github.com/HarryStevens/d3-regression/blob/master/LICENSE
// ... which was adapted from regression-js by Tom Alexander
// Source: https://github.com/Tom-Alexander/regression-js/blob/master/src/regression.js#L246
// License: https://github.com/Tom-Alexander/regression-js/blob/master/LICENSE
function regressionPoly(data, x, y, order) {
  // use more efficient methods for lower orders
  if (order === 1) return regressionLinear(data, x, y);
  if (order === 2) return regressionQuad(data, x, y);

  const [xv, yv, ux, uy] = points(data, x, y),
        n = xv.length,
        lhs = [],
        rhs = [],
        k = order + 1;

  let i, j, l, v, c;

  for (i=0; i<k; ++i) {
    for (l=0, v=0; l<n; ++l) {
      v += Math.pow(xv[l], i) * yv[l];
    }
    lhs.push(v);

    c = new Float64Array(k);
    for (j=0; j<k; ++j) {
      for (l=0, v=0; l<n; ++l) {
        v += Math.pow(xv[l], i + j);
      }
      c[j] = v;
    }
    rhs.push(c);
  }
  rhs.push(lhs);

  const coef = gaussianElimination(rhs),
        predict = x => {
          x -= ux;
          let y = uy + coef[0] + coef[1] * x + coef[2] * x * x;
          for (i=3; i<k; ++i) y += coef[i] * Math.pow(x, i);
          return y;
        };

  return {
    coef: uncenter(k, coef, -ux, uy),
    predict: predict,
    rSquared: rSquared(data, x, y, uy, predict)
  };
}

function uncenter(k, a, x, y) {
  const z = Array(k);
  let i, j, v, c;

  // initialize to zero
  for (i=0; i<k; ++i) z[i] = 0;

  // polynomial expansion
  for (i=k-1; i>=0; --i) {
    v = a[i];
    c = 1;
    z[i] += v;
    for (j=1; j<=i; ++j) {
      c *= (i + 1 - j) / j; // binomial coefficent
      z[i-j] += v * Math.pow(x, j) * c;
    }
  }

  // bias term
  z[0] += y;

  return z;
}

// Given an array for a two-dimensional matrix and the polynomial order,
// solve A * x = b using Gaussian elimination.
function gaussianElimination(matrix) {
  const n = matrix.length - 1,
        coef = [];

  let i, j, k, r, t;

  for (i = 0; i < n; ++i) {
    r = i; // max row
    for (j = i + 1; j < n; ++j) {
      if (Math.abs(matrix[i][j]) > Math.abs(matrix[i][r])) {
        r = j;
      }
    }

    for (k = i; k < n + 1; ++k) {
      t = matrix[k][i];
      matrix[k][i] = matrix[k][r];
      matrix[k][r] = t;
    }

    for (j = i + 1; j < n; ++j) {
      for (k = n; k >= i; k--) {
        matrix[k][j] -= (matrix[k][i] * matrix[i][j]) / matrix[i][i];
      }
    }
  }

  for (j = n - 1; j >= 0; --j) {
    t = 0;
    for (k = j + 1; k < n; ++k) {
      t += matrix[k][j] * coef[k];
    }
    coef[j] = (matrix[n][j] - t) / matrix[j][j];
  }

  return coef;
}

const maxiters = 2,
      epsilon = 1e-12;

// Adapted from science.js by Jason Davies
// Source: https://github.com/jasondavies/science.js/blob/master/src/stats/loess.js
// License: https://github.com/jasondavies/science.js/blob/master/LICENSE
function regressionLoess(data, x, y, bandwidth) {
  const [xv, yv, ux, uy] = points(data, x, y, true),
        n = xv.length,
        bw = Math.max(2, ~~(bandwidth * n)), // # nearest neighbors
        yhat = new Float64Array(n),
        residuals = new Float64Array(n),
        robustWeights = new Float64Array(n).fill(1);

  for (let iter = -1; ++iter <= maxiters; ) {
    const interval = [0, bw - 1];

    for (let i = 0; i < n; ++i) {
      const dx = xv[i],
            i0 = interval[0],
            i1 = interval[1],
            edge = (dx - xv[i0]) > (xv[i1] - dx) ? i0 : i1;

      let W = 0, X = 0, Y = 0, XY = 0, X2 = 0,
          denom = 1 / Math.abs(xv[edge] - dx || 1); // avoid singularity!

      for (let k = i0; k <= i1; ++k) {
        const xk = xv[k],
              yk = yv[k],
              w = tricube(Math.abs(dx - xk) * denom) * robustWeights[k],
              xkw = xk * w;

        W += w;
        X += xkw;
        Y += yk * w;
        XY += yk * xkw;
        X2 += xk * xkw;
      }

      // linear regression fit
      const [a, b] = ols(X / W, Y / W, XY / W, X2 / W);
      yhat[i] = a + b * dx;
      residuals[i] = Math.abs(yv[i] - yhat[i]);

      updateInterval(xv, i + 1, interval);
    }

    if (iter === maxiters) {
      break;
    }

    const medianResidual = median(residuals);
    if (Math.abs(medianResidual) < epsilon) break;

    for (let i = 0, arg, w; i < n; ++i){
      arg = residuals[i] / (6 * medianResidual);
      // default to epsilon (rather than zero) for large deviations
      // keeping weights tiny but non-zero prevents singularites
      robustWeights[i] = (arg >= 1) ? epsilon : ((w = 1 - arg * arg) * w);
    }
  }

  return output(xv, yhat, ux, uy);
}

// weighting kernel for local regression
function tricube(x) {
  return (x = 1 - x * x * x) * x * x;
}

// advance sliding window interval of nearest neighbors
function updateInterval(xv, i, interval) {
  let val = xv[i],
      left = interval[0],
      right = interval[1] + 1;

  if (right >= xv.length) return;

  // step right if distance to new right edge is <= distance to old left edge
  // step when distance is equal to ensure movement over duplicate x values
  while (i > left && (xv[right] - val) <= (val - xv[left])) {
    interval[0] = ++left;
    interval[1] = right;
    ++right;
  }
}

// generate smoothed output points
// average points with repeated x values
function output(xv, yhat, ux, uy) {
  const n = xv.length, out = [];
  let i = 0, cnt = 0, prev = [], v;

  for (; i<n; ++i) {
    v = xv[i] + ux;
    if (prev[0] === v) {
      // average output values via online update
      prev[1] += (yhat[i] - prev[1]) / (++cnt);
    } else {
      // add new output point
      cnt = 0;
      prev[1] += uy;
      prev = [v, yhat[i]];
      out.push(prev);
    }
  }
  prev[1] += uy;

  return out;
}

// subdivide up to accuracy of 0.1 degrees
const MIN_RADIANS = 0.1 * Math.PI / 180;

// Adaptively sample an interpolated function over a domain extent
function sampleCurve(f, extent, minSteps, maxSteps) {
  minSteps = minSteps || 25;
  maxSteps = Math.max(minSteps, maxSteps || 200);

  const point = x => [x, f(x)],
        minX = extent[0],
        maxX = extent[1],
        span = maxX - minX,
        stop = span / maxSteps,
        prev = [point(minX)],
        next = [];

  if (minSteps === maxSteps) {
    // no adaptation, sample uniform grid directly and return
    for (let i = 1; i < maxSteps; ++i) {
      prev.push(point(minX + (i / minSteps) * span));
    }
    prev.push(point(maxX));
    return prev;
  } else {
    // sample minimum points on uniform grid
    // then move on to perform adaptive refinement
    next.push(point(maxX));
    for (let i = minSteps; --i > 0;) {
      next.push(point(minX + (i / minSteps) * span));
    }
  }

  let p0 = prev[0],
      p1 = next[next.length - 1];

  while (p1) {
    // midpoint for potential curve subdivision
    const pm = point((p0[0] + p1[0]) / 2);

    if (pm[0] - p0[0] >= stop && angleDelta(p0, pm, p1) > MIN_RADIANS) {
      // maximum resolution has not yet been met, and
      // subdivision midpoint sufficiently different from endpoint
      // save subdivision, push midpoint onto the visitation stack
      next.push(pm);
    } else {
      // subdivision midpoint sufficiently similar to endpoint
      // skip subdivision, store endpoint, move to next point on the stack
      p0 = p1;
      prev.push(p1);
      next.pop();
    }
    p1 = next[next.length - 1];
  }

  return prev;
}

function angleDelta(p, q, r) {
  const a0 = Math.atan2(r[1] - p[1], r[0] - p[0]),
        a1 = Math.atan2(q[1] - p[1], q[0] - p[0]);
  return Math.abs(a0 - a1);
}

function TupleStore(key) {
  this._key = key ? field(key) : tupleid;
  this.reset();
}

var prototype$7 = TupleStore.prototype;

prototype$7.reset = function() {
  this._add = [];
  this._rem = [];
  this._ext = null;
  this._get = null;
  this._q = null;
};

prototype$7.add = function(v) {
  this._add.push(v);
};

prototype$7.rem = function(v) {
  this._rem.push(v);
};

prototype$7.values = function() {
  this._get = null;
  if (this._rem.length === 0) return this._add;

  var a = this._add,
      r = this._rem,
      k = this._key,
      n = a.length,
      m = r.length,
      x = Array(n - m),
      map = {}, i, j, v;

  // use unique key field to clear removed values
  for (i=0; i<m; ++i) {
    map[k(r[i])] = 1;
  }
  for (i=0, j=0; i<n; ++i) {
    if (map[k(v = a[i])]) {
      map[k(v)] = 0;
    } else {
      x[j++] = v;
    }
  }

  this._rem = [];
  return (this._add = x);
};

// memoizing statistics methods

prototype$7.distinct = function(get) {
  var v = this.values(),
      n = v.length,
      map = {},
      count = 0, s;

  while (--n >= 0) {
    s = get(v[n]) + '';
    if (!hasOwnProperty(map, s)) {
      map[s] = 1;
      ++count;
    }
  }

  return count;
};

prototype$7.extent = function(get) {
  if (this._get !== get || !this._ext) {
    var v = this.values(),
        i = extentIndex(v, get);
    this._ext = [v[i[0]], v[i[1]]];
    this._get = get;
  }
  return this._ext;
};

prototype$7.argmin = function(get) {
  return this.extent(get)[0] || {};
};

prototype$7.argmax = function(get) {
  return this.extent(get)[1] || {};
};

prototype$7.min = function(get) {
  var m = this.extent(get)[0];
  return m != null ? get(m) : undefined;
};

prototype$7.max = function(get) {
  var m = this.extent(get)[1];
  return m != null ? get(m) : undefined;
};

prototype$7.quartile = function(get) {
  if (this._get !== get || !this._q) {
    this._q = quartiles(this.values(), get);
    this._get = get;
  }
  return this._q;
};

prototype$7.q1 = function(get) {
  return this.quartile(get)[0];
};

prototype$7.q2 = function(get) {
  return this.quartile(get)[1];
};

prototype$7.q3 = function(get) {
  return this.quartile(get)[2];
};

prototype$7.ci = function(get) {
  if (this._get !== get || !this._ci) {
    this._ci = bootstrapCI(this.values(), 1000, 0.05, get);
    this._get = get;
  }
  return this._ci;
};

prototype$7.ci0 = function(get) {
  return this.ci(get)[0];
};

prototype$7.ci1 = function(get) {
  return this.ci(get)[1];
};

/**
 * Group-by aggregation operator.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors to groupby.
 * @param {Array<function(object): *>} [params.fields] - An array of accessors to aggregate.
 * @param {Array<string>} [params.ops] - An array of strings indicating aggregation operations.
 * @param {Array<string>} [params.as] - An array of output field names for aggregated values.
 * @param {boolean} [params.cross=false] - A flag indicating that the full
 *   cross-product of groupby values should be generated, including empty cells.
 *   If true, the drop parameter is ignored and empty cells are retained.
 * @param {boolean} [params.drop=true] - A flag indicating if empty cells should be removed.
 */
function Aggregate(params) {
  Transform.call(this, null, params);

  this._adds = []; // array of added output tuples
  this._mods = []; // array of modified output tuples
  this._alen = 0;  // number of active added tuples
  this._mlen = 0;  // number of active modified tuples
  this._drop = true;   // should empty aggregation cells be removed
  this._cross = false; // produce full cross-product of group-by values

  this._dims = [];   // group-by dimension accessors
  this._dnames = []; // group-by dimension names

  this._measures = []; // collection of aggregation monoids
  this._countOnly = false; // flag indicating only count aggregation
  this._counts = null; // collection of count fields
  this._prev = null;   // previous aggregation cells

  this._inputs = null;  // array of dependent input tuple field names
  this._outputs = null; // array of output tuple field names
}

Aggregate.Definition = {
  "type": "Aggregate",
  "metadata": {"generates": true, "changes": true},
  "params": [
    { "name": "groupby", "type": "field", "array": true },
    { "name": "ops", "type": "enum", "array": true, "values": ValidAggregateOps },
    { "name": "fields", "type": "field", "null": true, "array": true },
    { "name": "as", "type": "string", "null": true, "array": true },
    { "name": "drop", "type": "boolean", "default": true },
    { "name": "cross", "type": "boolean", "default": false },
    { "name": "key", "type": "field" }
  ]
};

var prototype$8 = inherits(Aggregate, Transform);

prototype$8.transform = function(_, pulse) {
  var aggr = this,
      out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS),
      mod = _.modified();

  aggr.stamp = out.stamp;

  if (aggr.value && (mod || pulse.modified(aggr._inputs, true))) {
    aggr._prev = aggr.value;
    aggr.value = mod ? aggr.init(_) : {};
    pulse.visit(pulse.SOURCE, t => aggr.add(t));
  } else {
    aggr.value = aggr.value || aggr.init(_);
    pulse.visit(pulse.REM, t => aggr.rem(t));
    pulse.visit(pulse.ADD, t => aggr.add(t));
  }

  // Indicate output fields and return aggregate tuples.
  out.modifies(aggr._outputs);

  // Should empty cells be dropped?
  aggr._drop = _.drop !== false;

  // If domain cross-product requested, generate empty cells as needed
  // and ensure that empty cells are not dropped
  if (_.cross && aggr._dims.length > 1) {
    aggr._drop = false;
    aggr.cross();
  }

  return aggr.changes(out);
};

prototype$8.cross = function() {
  var aggr = this,
      curr = aggr.value,
      dims = aggr._dnames,
      vals = dims.map(function() { return {}; }),
      n = dims.length;

  // collect all group-by domain values
  function collect(cells) {
    var key, i, t, v;
    for (key in cells) {
      t = cells[key].tuple;
      for (i=0; i<n; ++i) {
        vals[i][(v = t[dims[i]])] = v;
      }
    }
  }
  collect(aggr._prev);
  collect(curr);

  // iterate over key cross-product, create cells as needed
  function generate(base, tuple, index) {
    var name = dims[index],
        v = vals[index++],
        k, key;

    for (k in v) {
      tuple[name] = v[k];
      key = base ? base + '|' + k : k;
      if (index < n) generate(key, tuple, index);
      else if (!curr[key]) aggr.cell(key, tuple);
    }
  }
  generate('', {}, 0);
};

prototype$8.init = function(_) {
  // initialize input and output fields
  var inputs = (this._inputs = []),
      outputs = (this._outputs = []),
      inputMap = {};

  function inputVisit(get) {
    var fields = array(accessorFields(get)),
        i = 0, n = fields.length, f;
    for (; i<n; ++i) {
      if (!inputMap[f=fields[i]]) {
        inputMap[f] = 1;
        inputs.push(f);
      }
    }
  }

  // initialize group-by dimensions
  this._dims = array(_.groupby);
  this._dnames = this._dims.map(function(d) {
    var dname = accessorName(d);
    inputVisit(d);
    outputs.push(dname);
    return dname;
  });
  this.cellkey = _.key ? _.key : groupkey(this._dims);

  // initialize aggregate measures
  this._countOnly = true;
  this._counts = [];
  this._measures = [];

  var fields = _.fields || [null],
      ops = _.ops || ['count'],
      as = _.as || [],
      n = fields.length,
      map = {},
      field, op, m, mname, outname, i;

  if (n !== ops.length) {
    error('Unmatched number of fields and aggregate ops.');
  }

  for (i=0; i<n; ++i) {
    field = fields[i];
    op = ops[i];

    if (field == null && op !== 'count') {
      error('Null aggregate field specified.');
    }
    mname = accessorName(field);
    outname = measureName(op, mname, as[i]);
    outputs.push(outname);

    if (op === 'count') {
      this._counts.push(outname);
      continue;
    }

    m = map[mname];
    if (!m) {
      inputVisit(field);
      m = (map[mname] = []);
      m.field = field;
      this._measures.push(m);
    }

    if (op !== 'count') this._countOnly = false;
    m.push(createMeasure(op, outname));
  }

  this._measures = this._measures.map(function(m) {
    return compileMeasures(m, m.field);
  });

  return {}; // aggregation cells (this.value)
};

// -- Cell Management -----

prototype$8.cellkey = groupkey();

prototype$8.cell = function(key, t) {
  var cell = this.value[key];
  if (!cell) {
    cell = this.value[key] = this.newcell(key, t);
    this._adds[this._alen++] = cell;
  } else if (cell.num === 0 && this._drop && cell.stamp < this.stamp) {
    cell.stamp = this.stamp;
    this._adds[this._alen++] = cell;
  } else if (cell.stamp < this.stamp) {
    cell.stamp = this.stamp;
    this._mods[this._mlen++] = cell;
  }
  return cell;
};

prototype$8.newcell = function(key, t) {
  var cell = {
    key:   key,
    num:   0,
    agg:   null,
    tuple: this.newtuple(t, this._prev && this._prev[key]),
    stamp: this.stamp,
    store: false
  };

  if (!this._countOnly) {
    var measures = this._measures,
        n = measures.length, i;

    cell.agg = Array(n);
    for (i=0; i<n; ++i) {
      cell.agg[i] = new measures[i](cell);
    }
  }

  if (cell.store) {
    cell.data = new TupleStore();
  }

  return cell;
};

prototype$8.newtuple = function(t, p) {
  var names = this._dnames,
      dims = this._dims,
      x = {}, i, n;

  for (i=0, n=dims.length; i<n; ++i) {
    x[names[i]] = dims[i](t);
  }

  return p ? replace(p.tuple, x) : ingest(x);
};

// -- Process Tuples -----

prototype$8.add = function(t) {
  var key = this.cellkey(t),
      cell = this.cell(key, t),
      agg, i, n;

  cell.num += 1;
  if (this._countOnly) return;

  if (cell.store) cell.data.add(t);

  agg = cell.agg;
  for (i=0, n=agg.length; i<n; ++i) {
    agg[i].add(agg[i].get(t), t);
  }
};

prototype$8.rem = function(t) {
  var key = this.cellkey(t),
      cell = this.cell(key, t),
      agg, i, n;

  cell.num -= 1;
  if (this._countOnly) return;

  if (cell.store) cell.data.rem(t);

  agg = cell.agg;
  for (i=0, n=agg.length; i<n; ++i) {
    agg[i].rem(agg[i].get(t), t);
  }
};

prototype$8.celltuple = function(cell) {
  var tuple = cell.tuple,
      counts = this._counts,
      agg, i, n;

  // consolidate stored values
  if (cell.store) {
    cell.data.values();
  }

  // update tuple properties
  for (i=0, n=counts.length; i<n; ++i) {
    tuple[counts[i]] = cell.num;
  }
  if (!this._countOnly) {
    agg = cell.agg;
    for (i=0, n=agg.length; i<n; ++i) {
      agg[i].set(tuple);
    }
  }

  return tuple;
};

prototype$8.changes = function(out) {
  var adds = this._adds,
      mods = this._mods,
      prev = this._prev,
      drop = this._drop,
      add = out.add,
      rem = out.rem,
      mod = out.mod,
      cell, key, i, n;

  if (prev) for (key in prev) {
    cell = prev[key];
    if (!drop || cell.num) rem.push(cell.tuple);
  }

  for (i=0, n=this._alen; i<n; ++i) {
    add.push(this.celltuple(adds[i]));
    adds[i] = null; // for garbage collection
  }

  for (i=0, n=this._mlen; i<n; ++i) {
    cell = mods[i];
    (cell.num === 0 && drop ? rem : mod).push(this.celltuple(cell));
    mods[i] = null; // for garbage collection
  }

  this._alen = this._mlen = 0; // reset list of active cells
  this._prev = null;
  return out;
};

// epsilon bias to offset floating point error (#1737)
const EPSILON = 1e-14;

/**
 * Generates a binning function for discretizing data.
 * @constructor
 * @param {object} params - The parameters for this operator. The
 *   provided values should be valid options for the {@link bin} function.
 * @param {function(object): *} params.field - The data field to bin.
 */
function Bin(params) {
  Transform.call(this, null, params);
}

Bin.Definition = {
  "type": "Bin",
  "metadata": {"modifies": true},
  "params": [
    { "name": "field", "type": "field", "required": true },
    { "name": "interval", "type": "boolean", "default": true },
    { "name": "anchor", "type": "number" },
    { "name": "maxbins", "type": "number", "default": 20 },
    { "name": "base", "type": "number", "default": 10 },
    { "name": "divide", "type": "number", "array": true, "default": [5, 2] },
    { "name": "extent", "type": "number", "array": true, "length": 2, "required": true },
    { "name": "span", "type": "number" },
    { "name": "step", "type": "number" },
    { "name": "steps", "type": "number", "array": true },
    { "name": "minstep", "type": "number", "default": 0 },
    { "name": "nice", "type": "boolean", "default": true },
    { "name": "name", "type": "string" },
    { "name": "as", "type": "string", "array": true, "length": 2, "default": ["bin0", "bin1"] }
  ]
};

var prototype$9 = inherits(Bin, Transform);

prototype$9.transform = function(_, pulse) {
  var band = _.interval !== false,
      bins = this._bins(_),
      start = bins.start,
      step = bins.step,
      as = _.as || ['bin0', 'bin1'],
      b0 = as[0],
      b1 = as[1],
      flag;

  if (_.modified()) {
    pulse = pulse.reflow(true);
    flag = pulse.SOURCE;
  } else {
    flag = pulse.modified(accessorFields(_.field)) ? pulse.ADD_MOD : pulse.ADD;
  }

  pulse.visit(flag, band
    ? function(t) {
        var v = bins(t);
        // minimum bin value (inclusive)
        t[b0] = v;
        // maximum bin value (exclusive)
        // use convoluted math for better floating point agreement
        // see https://github.com/vega/vega/issues/830
        // infinite values propagate through this formula! #2227
        t[b1] = v == null ? null : start + step * (1 + (v - start) / step);
      }
    : function(t) { t[b0] = bins(t); }
  );

  return pulse.modifies(band ? as : b0);
};

prototype$9._bins = function(_) {
  if (this.value && !_.modified()) {
    return this.value;
  }

  var field = _.field,
      bins  = bin(_),
      step  = bins.step,
      start = bins.start,
      stop  = start + Math.ceil((bins.stop - start) / step) * step,
      a, d;

  if ((a = _.anchor) != null) {
    d = a - (start + step * Math.floor((a - start) / step));
    start += d;
    stop += d;
  }

  var f = function(t) {
    var v = field(t);
    return v == null ? null
      : v < start ? -Infinity
      : v > stop ? +Infinity
      : (
          v = Math.max(start, Math.min(+v, stop - step)),
          start + step * Math.floor(EPSILON + (v - start) / step)
        );
  };

  f.start = start;
  f.stop = bins.stop;
  f.step = step;

  return this.value = accessor(
    f,
    accessorFields(field),
    _.name || 'bin_' + accessorName(field)
  );
};

function SortedList(idFunc, source, input) {
  var $ = idFunc,
      data = source || [],
      add = input || [],
      rem = {},
      cnt = 0;

  return {
    add: function(t) { add.push(t); },
    remove: function(t) { rem[$(t)] = ++cnt; },
    size: function() { return data.length; },
    data: function(compare, resort) {
      if (cnt) {
        data = data.filter(function(t) { return !rem[$(t)]; });
        rem = {};
        cnt = 0;
      }
      if (resort && compare) {
        data.sort(compare);
      }
      if (add.length) {
        data = compare
          ? merge(compare, data, add.sort(compare))
          : data.concat(add);
        add = [];
      }
      return data;
    }
  }
}

/**
 * Collects all data tuples that pass through this operator.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(*,*): number} [params.sort] - An optional
 *   comparator function for additionally sorting the collected tuples.
 */
function Collect(params) {
  Transform.call(this, [], params);
}

Collect.Definition = {
  "type": "Collect",
  "metadata": {"source": true},
  "params": [
    { "name": "sort", "type": "compare" }
  ]
};

var prototype$a = inherits(Collect, Transform);

prototype$a.transform = function(_, pulse) {
  var out = pulse.fork(pulse.ALL),
      list = SortedList(tupleid, this.value, out.materialize(out.ADD).add),
      sort = _.sort,
      mod = pulse.changed() || (sort &&
            (_.modified('sort') || pulse.modified(sort.fields)));

  out.visit(out.REM, list.remove);

  this.modified(mod);
  this.value = out.source = list.data(stableCompare(sort), mod);

  // propagate tree root if defined
  if (pulse.source && pulse.source.root) {
    this.value.root = pulse.source.root;
  }

  return out;
};

/**
 * Generates a comparator function.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<string|function>} params.fields - The fields to compare.
 * @param {Array<string>} [params.orders] - The sort orders.
 *   Each entry should be one of "ascending" (default) or "descending".
 */
function Compare(params) {
  Operator.call(this, null, update$1, params);
}

inherits(Compare, Operator);

function update$1(_) {
  return (this.value && !_.modified())
    ? this.value
    : compare(_.fields, _.orders);
}

/**
 * Count regexp-defined pattern occurrences in a text field.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - An accessor for the text field.
 * @param {string} [params.pattern] - RegExp string defining the text pattern.
 * @param {string} [params.case] - One of 'lower', 'upper' or null (mixed) case.
 * @param {string} [params.stopwords] - RegExp string of words to ignore.
 */
function CountPattern(params) {
  Transform.call(this, null, params);
}

CountPattern.Definition = {
  "type": "CountPattern",
  "metadata": {"generates": true, "changes": true},
  "params": [
    { "name": "field", "type": "field", "required": true },
    { "name": "case", "type": "enum", "values": ["upper", "lower", "mixed"], "default": "mixed" },
    { "name": "pattern", "type": "string", "default": "[\\w\"]+" },
    { "name": "stopwords", "type": "string", "default": "" },
    { "name": "as", "type": "string", "array": true, "length": 2, "default": ["text", "count"] }
  ]
};

function tokenize(text, tcase, match) {
  switch (tcase) {
    case 'upper': text = text.toUpperCase(); break;
    case 'lower': text = text.toLowerCase(); break;
  }
  return text.match(match);
}

var prototype$b = inherits(CountPattern, Transform);

prototype$b.transform = function(_, pulse) {
  function process(update) {
    return function(tuple) {
      var tokens = tokenize(get(tuple), _.case, match) || [], t;
      for (var i=0, n=tokens.length; i<n; ++i) {
        if (!stop.test(t = tokens[i])) update(t);
      }
    };
  }

  var init = this._parameterCheck(_, pulse),
      counts = this._counts,
      match = this._match,
      stop = this._stop,
      get = _.field,
      as = _.as || ['text', 'count'],
      add = process(function(t) { counts[t] = 1 + (counts[t] || 0); }),
      rem = process(function(t) { counts[t] -= 1; });

  if (init) {
    pulse.visit(pulse.SOURCE, add);
  } else {
    pulse.visit(pulse.ADD, add);
    pulse.visit(pulse.REM, rem);
  }

  return this._finish(pulse, as); // generate output tuples
};

prototype$b._parameterCheck = function(_, pulse) {
  var init = false;

  if (_.modified('stopwords') || !this._stop) {
    this._stop = new RegExp('^' + (_.stopwords || '') + '$', 'i');
    init = true;
  }

  if (_.modified('pattern') || !this._match) {
    this._match = new RegExp((_.pattern || '[\\w\']+'), 'g');
    init = true;
  }

  if (_.modified('field') || pulse.modified(_.field.fields)) {
    init = true;
  }

  if (init) this._counts = {};
  return init;
};

prototype$b._finish = function(pulse, as) {
  var counts = this._counts,
      tuples = this._tuples || (this._tuples = {}),
      text = as[0],
      count = as[1],
      out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS),
      w, t, c;

  for (w in counts) {
    t = tuples[w];
    c = counts[w] || 0;
    if (!t && c) {
      tuples[w] = (t = ingest({}));
      t[text] = w;
      t[count] = c;
      out.add.push(t);
    } else if (c === 0) {
      if (t) out.rem.push(t);
      counts[w] = null;
      tuples[w] = null;
    } else if (t[count] !== c) {
      t[count] = c;
      out.mod.push(t);
    }
  }

  return out.modifies(as);
};

/**
 * Perform a cross-product of a tuple stream with itself.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object):boolean} [params.filter] - An optional filter
 *   function for selectively including tuples in the cross product.
 * @param {Array<string>} [params.as] - The names of the output fields.
 */
function Cross(params) {
  Transform.call(this, null, params);
}

Cross.Definition = {
  "type": "Cross",
  "metadata": {"generates": true},
  "params": [
    { "name": "filter", "type": "expr" },
    { "name": "as", "type": "string", "array": true, "length": 2, "default": ["a", "b"] }
  ]
};

var prototype$c = inherits(Cross, Transform);

prototype$c.transform = function(_, pulse) {
  var out = pulse.fork(pulse.NO_SOURCE),
      data = this.value,
      as = _.as || ['a', 'b'],
      a = as[0], b = as[1],
      reset = !data
          || pulse.changed(pulse.ADD_REM)
          || _.modified('as')
          || _.modified('filter');

  if (reset) {
    if (data) out.rem = data;
    data = pulse.materialize(pulse.SOURCE).source;
    out.add = this.value = cross(data, a, b, _.filter || truthy);
  } else {
    out.mod = data;
  }

  out.source = this.value;
  return out.modifies(as);
};

function cross(input, a, b, filter) {
  var data = [],
      t = {},
      n = input.length,
      i = 0,
      j, left;

  for (; i<n; ++i) {
    t[a] = left = input[i];
    for (j=0; j<n; ++j) {
      t[b] = input[j];
      if (filter(t)) {
        data.push(ingest(t));
        t = {};
        t[a] = left;
      }
    }
  }

  return data;
}

var Distributions = {
  kde:       randomKDE,
  mixture:   randomMixture,
  normal:    randomNormal,
  lognormal: randomLogNormal,
  uniform:   randomUniform
};

var DISTRIBUTIONS = 'distributions',
    FUNCTION = 'function',
    FIELD = 'field';

/**
 * Parse a parameter object for a probability distribution.
 * @param {object} def - The distribution parameter object.
 * @param {function():Array<object>} - A method for requesting
 *   source data. Used for distributions (such as KDE) that
 *   require sample data points. This method will only be
 *   invoked if the 'from' parameter for a target data source
 *   is not provided. Typically this method returns backing
 *   source data for a Pulse object.
 * @return {object} - The output distribution object.
 */
function parse$2(def, data) {
  var func = def[FUNCTION];
  if (!hasOwnProperty(Distributions, func)) {
    error('Unknown distribution function: ' + func);
  }

  var d = Distributions[func]();

  for (var name in def) {
    // if data field, extract values
    if (name === FIELD) {
      d.data((def.from || data()).map(def[name]));
    }

    // if distribution mixture, recurse to parse each definition
    else if (name === DISTRIBUTIONS) {
      d[name](def[name].map(function(_) { return parse$2(_, data); }));
    }

    // otherwise, simply set the parameter
    else if (typeof d[name] === FUNCTION) {
      d[name](def[name]);
    }
  }

  return d;
}

/**
 * Grid sample points for a probability density. Given a distribution and
 * a sampling extent, will generate points suitable for plotting either
 * PDF (probability density function) or CDF (cumulative distribution
 * function) curves.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {object} params.distribution - The probability distribution. This
 *   is an object parameter dependent on the distribution type.
 * @param {string} [params.method='pdf'] - The distribution method to sample.
 *   One of 'pdf' or 'cdf'.
 * @param {Array<number>} [params.extent] - The [min, max] extent over which
 *   to sample the distribution. This argument is required in most cases, but
 *   can be omitted if the distribution (e.g., 'kde') supports a 'data' method
 *   that returns numerical sample points from which the extent can be deduced.
 * @param {number} [params.minsteps=25] - The minimum number of curve samples
 *   for plotting the density.
 * @param {number} [params.maxsteps=200] - The maximum number of curve samples
 *   for plotting the density.
 * @param {number} [params.steps] - The exact number of curve samples for
 *   plotting the density. If specified, overrides both minsteps and maxsteps
 *   to set an exact number of uniform samples. Useful in conjunction with
 *   a fixed extent to ensure consistent sample points for stacked densities.
 */
function Density(params) {
  Transform.call(this, null, params);
}

var distributions = [
  {
    "key": {"function": "normal"},
    "params": [
      { "name": "mean", "type": "number", "default": 0 },
      { "name": "stdev", "type": "number", "default": 1 }
    ]
  },
  {
    "key": {"function": "lognormal"},
    "params": [
      { "name": "mean", "type": "number", "default": 0 },
      { "name": "stdev", "type": "number", "default": 1 }
    ]
  },
  {
    "key": {"function": "uniform"},
    "params": [
      { "name": "min", "type": "number", "default": 0 },
      { "name": "max", "type": "number", "default": 1 }
    ]
  },
  {
    "key": {"function": "kde"},
    "params": [
      { "name": "field", "type": "field", "required": true },
      { "name": "from", "type": "data" },
      { "name": "bandwidth", "type": "number", "default": 0 }
    ]
  }
];

var mixture = {
  "key": {"function": "mixture"},
  "params": [
    { "name": "distributions", "type": "param", "array": true,
      "params": distributions },
    { "name": "weights", "type": "number", "array": true }
  ]
};

Density.Definition = {
  "type": "Density",
  "metadata": {"generates": true},
  "params": [
    { "name": "extent", "type": "number", "array": true, "length": 2 },
    { "name": "steps", "type": "number" },
    { "name": "minsteps", "type": "number", "default": 25 },
    { "name": "maxsteps", "type": "number", "default": 200 },
    { "name": "method", "type": "string", "default": "pdf",
      "values": ["pdf", "cdf"] },
    { "name": "distribution", "type": "param",
      "params": distributions.concat(mixture) },
    { "name": "as", "type": "string", "array": true,
      "default": ["value", "density"] }
  ]
};

var prototype$d = inherits(Density, Transform);

prototype$d.transform = function(_, pulse) {
  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS);

  if (!this.value || pulse.changed() || _.modified()) {
    var dist = parse$2(_.distribution, source(pulse)),
        minsteps = _.steps || _.minsteps || 25,
        maxsteps = _.steps || _.maxsteps || 200,
        method = _.method || 'pdf';

    if (method !== 'pdf' && method !== 'cdf') {
      error('Invalid density method: ' + method);
    }
    if (!_.extent && !dist.data) {
      error('Missing density extent parameter.');
    }
    method = dist[method];

    var as = _.as || ['value', 'density'],
        domain = _.extent || extent(dist.data()),
        values = sampleCurve(method, domain, minsteps, maxsteps).map(v => {
          var tuple = {};
          tuple[as[0]] = v[0];
          tuple[as[1]] = v[1];
          return ingest(tuple);
        });

    if (this.value) out.rem = this.value;
    this.value = out.add = out.source = values;
  }

  return out;
};

function source(pulse) {
  return function() { return pulse.materialize(pulse.SOURCE).source; };
}

// use either provided alias or accessor field name
function fieldNames(fields, as) {
  if (!fields) return null;
  return fields.map(function(f, i) {
    return as[i] || accessorName(f);
  });
}

function partition(data, groupby, field) {
  var groups = [],
      get = function(f) { return f(t); },
      map, i, n, t, k, g;

  // partition data points into groups
  if (groupby == null) {
    groups.push(data.map(field));
  } else {
    for (map={}, i=0, n=data.length; i<n; ++i) {
      t = data[i];
      k = groupby.map(get);
      g = map[k];
      if (!g) {
        map[k] = (g = []);
        g.dims = k;
        groups.push(g);
      }
      g.push(field(t));
    }
  }

  return groups;
}

const Output = 'bin';

/**
 * Dot density binning for dot plot construction.
 * Based on Leland Wilkinson, Dot Plots, The American Statistician, 1999.
 * https://www.cs.uic.edu/~wilkinson/Publications/dotplots.pdf
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The value field to bin.
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors to groupby.
 * @param {number} [params.step] - The step size (bin width) within which dots should be
 *   stacked. Defaults to 1/30 of the extent of the data *field*.
 * @param {boolean} [params.smooth=false] - A boolean flag indicating if dot density
 *   stacks should be smoothed to reduce variance.
 */
function DotBin(params) {
  Transform.call(this, null, params);
}

DotBin.Definition = {
  "type": "DotBin",
  "metadata": {"modifies": true},
  "params": [
    { "name": "field", "type": "field", "required": true },
    { "name": "groupby", "type": "field", "array": true },
    { "name": "step", "type": "number" },
    { "name": "smooth", "type": "boolean", "default": false },
    { "name": "as", "type": "string", "default": Output }
  ]
};

const prototype$e = inherits(DotBin, Transform);

prototype$e.transform = function(_, pulse) {
  if (this.value && !(_.modified() || pulse.changed())) {
    return pulse; // early exit
  }

  const source = pulse.materialize(pulse.SOURCE).source,
        groups = partition(pulse.source, _.groupby, identity),
        smooth = _.smooth || false,
        field = _.field,
        step = _.step || autostep(source, field),
        sort = stableCompare((a, b) => field(a) - field(b)),
        as = _.as || Output,
        n = groups.length;

  // compute dotplot bins per group
  let min = Infinity, max = -Infinity, i = 0, j;
  for (; i<n; ++i) {
    const g = groups[i].sort(sort);
    j = -1;
    for (const v of dotbin(g, step, smooth, field)) {
      if (v < min) min = v;
      if (v > max) max = v;
      g[++j][as] = v;
    }
  }

  this.value = {
    start: min,
    stop: max,
    step: step
  };
  return pulse.reflow(true).modifies(as);
};

function autostep(data, field) {
  return span(extent(data, field)) / 30;
}

/**
 * Wraps an expression function with access to external parameters.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function} params.expr - The expression function. The
 *  function should accept both a datum and a parameter object.
 *  This operator's value will be a new function that wraps the
 *  expression function with access to this operator's parameters.
 */
function Expression(params) {
  Operator.call(this, null, update$2, params);
  this.modified(true);
}

inherits(Expression, Operator);

function update$2(_) {
  var expr = _.expr;
  return this.value && !_.modified('expr')
    ? this.value
    : accessor(
        datum => expr(datum, _),
        accessorFields(expr),
        accessorName(expr)
      );
}

/**
 * Computes extents (min/max) for a data field.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The field over which to compute extends.
 */
function Extent(params) {
  Transform.call(this, [undefined, undefined], params);
}

Extent.Definition = {
  "type": "Extent",
  "metadata": {},
  "params": [
    { "name": "field", "type": "field", "required": true }
  ]
};

var prototype$f = inherits(Extent, Transform);

prototype$f.transform = function(_, pulse) {
  var extent = this.value,
      field = _.field,
      min = extent[0],
      max = extent[1],
      mod;

  mod = pulse.changed()
     || pulse.modified(field.fields)
     || _.modified('field');

  if (mod || min == null) {
    min = +Infinity;
    max = -Infinity;
  }

  pulse.visit(mod ? pulse.SOURCE : pulse.ADD, function(t) {
    var v = field(t);
    if (v != null) {
      // coerce to number
      v = +v;
      // NaNs will fail all comparisons!
      if (v < min) min = v;
      if (v > max) max = v;
    }
  });

  if (!Number.isFinite(min) || !Number.isFinite(max)) {
    let name = accessorName(field);
    if (name) name = ` for field "${name}"`;
    pulse.dataflow.warn(`Infinite extent${name}: [${min}, ${max}]`);
    min = max = undefined;
  }
  this.value = [min, max];
};

/**
 * Provides a bridge between a parent transform and a target subflow that
 * consumes only a subset of the tuples that pass through the parent.
 * @constructor
 * @param {Pulse} pulse - A pulse to use as the value of this operator.
 * @param {Transform} parent - The parent transform (typically a Facet instance).
 * @param {Transform} target - A transform that receives the subflow of tuples.
 */
function Subflow(pulse, parent) {
  Operator.call(this, pulse);
  this.parent = parent;
}

var prototype$g = inherits(Subflow, Operator);

prototype$g.connect = function(target) {
  this.targets().add(target);
  return (target.source = this);
};

/**
 * Add an 'add' tuple to the subflow pulse.
 * @param {Tuple} t - The tuple being added.
 */
prototype$g.add = function(t) {
  this.value.add.push(t);
};

/**
 * Add a 'rem' tuple to the subflow pulse.
 * @param {Tuple} t - The tuple being removed.
 */
prototype$g.rem = function(t) {
  this.value.rem.push(t);
};

/**
 * Add a 'mod' tuple to the subflow pulse.
 * @param {Tuple} t - The tuple being modified.
 */
prototype$g.mod = function(t) {
  this.value.mod.push(t);
};

/**
 * Re-initialize this operator's pulse value.
 * @param {Pulse} pulse - The pulse to copy from.
 * @see Pulse.init
 */
prototype$g.init = function(pulse) {
  this.value.init(pulse, pulse.NO_SOURCE);
};

/**
 * Evaluate this operator. This method overrides the
 * default behavior to simply return the contained pulse value.
 * @return {Pulse}
 */
prototype$g.evaluate = function() {
  // assert: this.value.stamp === pulse.stamp
  return this.value;
};

/**
 * Facets a dataflow into a set of subflows based on a key.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(Dataflow, string): Operator} params.subflow - A function
 *   that generates a subflow of operators and returns its root operator.
 * @param {function(object): *} params.key - The key field to facet by.
 */
function Facet(params) {
  Transform.call(this, {}, params);
  this._keys = fastmap(); // cache previously calculated key values

  // keep track of active subflows, use as targets array for listeners
  // this allows us to limit propagation to only updated subflows
  var a = this._targets = [];
  a.active = 0;
  a.forEach = function(f) {
    for (var i=0, n=a.active; i<n; ++i) f(a[i], i, a);
  };
}

var prototype$h = inherits(Facet, Transform);

prototype$h.activate = function(flow) {
  this._targets[this._targets.active++] = flow;
};

prototype$h.subflow = function(key, flow, pulse, parent) {
  var flows = this.value,
      sf = hasOwnProperty(flows, key) && flows[key],
      df, p;

  if (!sf) {
    p = parent || (p = this._group[key]) && p.tuple;
    df = pulse.dataflow;
    sf = df.add(new Subflow(pulse.fork(pulse.NO_SOURCE), this))
      .connect(flow(df, key, p));
    flows[key] = sf;
    this.activate(sf);
  } else if (sf.value.stamp < pulse.stamp) {
    sf.init(pulse);
    this.activate(sf);
  }

  return sf;
};

prototype$h.transform = function(_, pulse) {
  var df = pulse.dataflow,
      self = this,
      key = _.key,
      flow = _.subflow,
      cache = this._keys,
      rekey = _.modified('key');

  function subflow(key) {
    return self.subflow(key, flow, pulse);
  }

  this._group = _.group || {};
  this._targets.active = 0; // reset list of active subflows

  pulse.visit(pulse.REM, function(t) {
    var id = tupleid(t),
        k = cache.get(id);
    if (k !== undefined) {
      cache.delete(id);
      subflow(k).rem(t);
    }
  });

  pulse.visit(pulse.ADD, function(t) {
    var k = key(t);
    cache.set(tupleid(t), k);
    subflow(k).add(t);
  });

  if (rekey || pulse.modified(key.fields)) {
    pulse.visit(pulse.MOD, function(t) {
      var id = tupleid(t),
          k0 = cache.get(id),
          k1 = key(t);
      if (k0 === k1) {
        subflow(k1).mod(t);
      } else {
        cache.set(id, k1);
        subflow(k0).rem(t);
        subflow(k1).add(t);
      }
    });
  } else if (pulse.changed(pulse.MOD)) {
    pulse.visit(pulse.MOD, function(t) {
      subflow(cache.get(tupleid(t))).mod(t);
    });
  }

  if (rekey) {
    pulse.visit(pulse.REFLOW, function(t) {
      var id = tupleid(t),
          k0 = cache.get(id),
          k1 = key(t);
      if (k0 !== k1) {
        cache.set(id, k1);
        subflow(k0).rem(t);
        subflow(k1).add(t);
      }
    });
  }

  if (cache.empty > df.cleanThreshold) df.runAfter(cache.clean);
  return pulse;
};

/**
 * Generates one or more field accessor functions.
 * If the 'name' parameter is an array, an array of field accessors
 * will be created and the 'as' parameter will be ignored.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {string} params.name - The field name(s) to access.
 * @param {string} params.as - The accessor function name.
 */
function Field(params) {
  Operator.call(this, null, update$3, params);
}

inherits(Field, Operator);

function update$3(_) {
  return (this.value && !_.modified()) ? this.value
    : isArray(_.name) ? array(_.name).map(function(f) { return field(f); })
    : field(_.name, _.as);
}

/**
 * Filters data tuples according to a predicate function.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.expr - The predicate expression function
 *   that determines a tuple's filter status. Truthy values pass the filter.
 */
function Filter(params) {
  Transform.call(this, fastmap(), params);
}

Filter.Definition = {
  "type": "Filter",
  "metadata": {"changes": true},
  "params": [
    { "name": "expr", "type": "expr", "required": true }
  ]
};

var prototype$i = inherits(Filter, Transform);

prototype$i.transform = function(_, pulse) {
  var df = pulse.dataflow,
      cache = this.value, // cache ids of filtered tuples
      output = pulse.fork(),
      add = output.add,
      rem = output.rem,
      mod = output.mod,
      test = _.expr,
      isMod = true;

  pulse.visit(pulse.REM, function(t) {
    var id = tupleid(t);
    if (!cache.has(id)) rem.push(t);
    else cache.delete(id);
  });

  pulse.visit(pulse.ADD, function(t) {
    if (test(t, _)) add.push(t);
    else cache.set(tupleid(t), 1);
  });

  function revisit(t) {
    var id = tupleid(t),
        b = test(t, _),
        s = cache.get(id);
    if (b && s) {
      cache.delete(id);
      add.push(t);
    } else if (!b && !s) {
      cache.set(id, 1);
      rem.push(t);
    } else if (isMod && b && !s) {
      mod.push(t);
    }
  }

  pulse.visit(pulse.MOD, revisit);

  if (_.modified()) {
    isMod = false;
    pulse.visit(pulse.REFLOW, revisit);
  }

  if (cache.empty > df.cleanThreshold) df.runAfter(cache.clean);
  return output;
};

/**
 * Flattens array-typed field values into new data objects.
 * If multiple fields are specified, they are treated as parallel arrays,
 * with output values included for each matching index (or null if missing).
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<function(object): *>} params.fields - An array of field
 *   accessors for the tuple fields that should be flattened.
 * @param {string} [params.index] - Optional output field name for index
 *   value. If unspecified, no index field is included in the output.
 * @param {Array<string>} [params.as] - Output field names for flattened
 *   array fields. Any unspecified fields will use the field name provided
 *   by the fields accessors.
 */
function Flatten(params) {
  Transform.call(this, [], params);
}

Flatten.Definition = {
  "type": "Flatten",
  "metadata": {"generates": true},
  "params": [
    { "name": "fields", "type": "field", "array": true, "required": true },
    { "name": "index", "type": "string" },
    { "name": "as", "type": "string", "array": true }
  ]
};

var prototype$j = inherits(Flatten, Transform);

prototype$j.transform = function(_, pulse) {
  var out = pulse.fork(pulse.NO_SOURCE),
      fields = _.fields,
      as = fieldNames(fields, _.as || []),
      index = _.index || null,
      m = as.length;

  // remove any previous results
  out.rem = this.value;

  // generate flattened tuples
  pulse.visit(pulse.SOURCE, function(t) {
    var arrays = fields.map(f => f(t)),
        maxlen = arrays.reduce((l, a) => Math.max(l, a.length), 0),
        i = 0, j, d, v;

    for (; i<maxlen; ++i) {
      d = derive(t);
      for (j=0; j<m; ++j) {
        d[as[j]] = (v = arrays[j][i]) == null ? null : v;
      }
      if (index) {
        d[index] = i;
      }
      out.add.push(d);
    }
  });

  this.value = out.source = out.add;
  if (index) out.modifies(index);
  return out.modifies(as);
};

/**
 * Folds one more tuple fields into multiple tuples in which the field
 * name and values are available under new 'key' and 'value' fields.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.fields - An array of field accessors
 *   for the tuple fields that should be folded.
 * @param {Array<string>} [params.as] - Output field names for folded key
 *   and value fields, defaults to ['key', 'value'].
 */
function Fold(params) {
  Transform.call(this, [], params);
}

Fold.Definition = {
  "type": "Fold",
  "metadata": {"generates": true},
  "params": [
    { "name": "fields", "type": "field", "array": true, "required": true },
    { "name": "as", "type": "string", "array": true, "length": 2, "default": ["key", "value"] }
  ]
};

var prototype$k = inherits(Fold, Transform);

prototype$k.transform = function(_, pulse) {
  var out = pulse.fork(pulse.NO_SOURCE),
      fields = _.fields,
      fnames = fields.map(accessorName),
      as = _.as || ['key', 'value'],
      k = as[0],
      v = as[1],
      n = fields.length;

  out.rem = this.value;

  pulse.visit(pulse.SOURCE, function(t) {
    for (var i=0, d; i<n; ++i) {
      d = derive(t);
      d[k] = fnames[i];
      d[v] = fields[i](t);
      out.add.push(d);
    }
  });

  this.value = out.source = out.add;
  return out.modifies(as);
};

/**
 * Invokes a function for each data tuple and saves the results as a new field.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.expr - The formula function to invoke for each tuple.
 * @param {string} params.as - The field name under which to save the result.
 * @param {boolean} [params.initonly=false] - If true, the formula is applied to
 *   added tuples only, and does not update in response to modifications.
 */
function Formula(params) {
  Transform.call(this, null, params);
}

Formula.Definition = {
  "type": "Formula",
  "metadata": {"modifies": true},
  "params": [
    { "name": "expr", "type": "expr", "required": true },
    { "name": "as", "type": "string", "required": true },
    { "name": "initonly", "type": "boolean" }
  ]
};

var prototype$l = inherits(Formula, Transform);

prototype$l.transform = function(_, pulse) {
  var func = _.expr,
      as = _.as,
      mod = _.modified(),
      flag = _.initonly ? pulse.ADD
        : mod ? pulse.SOURCE
        : pulse.modified(func.fields) || pulse.modified(as) ? pulse.ADD_MOD
        : pulse.ADD;

  if (mod) {
    // parameters updated, need to reflow
    pulse = pulse.materialize().reflow(true);
  }

  if (!_.initonly) {
    pulse.modifies(as);
  }

  return pulse.visit(flag, t => t[as] = func(t, _));
};

/**
 * Generates data tuples using a provided generator function.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(Parameters): object} params.generator - A tuple generator
 *   function. This function is given the operator parameters as input.
 *   Changes to any additional parameters will not trigger re-calculation
 *   of previously generated tuples. Only future tuples are affected.
 * @param {number} params.size - The number of tuples to produce.
 */
function Generate(params) {
  Transform.call(this, [], params);
}

var prototype$m = inherits(Generate, Transform);

prototype$m.transform = function(_, pulse) {
  var data = this.value,
      out = pulse.fork(pulse.ALL),
      num = _.size - data.length,
      gen = _.generator,
      add, rem, t;

  if (num > 0) {
    // need more tuples, generate and add
    for (add=[]; --num >= 0;) {
      add.push(t = ingest(gen(_)));
      data.push(t);
    }
    out.add = out.add.length
      ? out.materialize(out.ADD).add.concat(add)
      : add;
  } else {
    // need fewer tuples, remove
    rem = data.slice(0, -num);
    out.rem = out.rem.length
      ? out.materialize(out.REM).rem.concat(rem)
      : rem;
    data = data.slice(-num);
  }

  out.source = this.value = data;
  return out;
};

var Methods = {
  value: 'value',
  median: median,
  mean: mean,
  min: min,
  max: max
};

var Empty = [];

/**
 * Impute missing values.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The value field to impute.
 * @param {Array<function(object): *>} [params.groupby] - An array of
 *   accessors to determine series within which to perform imputation.
 * @param {function(object): *} params.key - An accessor for a key value.
 *   Each key value should be unique within a group. New tuples will be
 *   imputed for any key values that are not found within a group.
 * @param {Array<*>} [params.keyvals] - Optional array of required key
 *   values. New tuples will be imputed for any key values that are not
 *   found within a group. In addition, these values will be automatically
 *   augmented with the key values observed in the input data.
 * @param {string} [method='value'] - The imputation method to use. One of
 *   'value', 'mean', 'median', 'max', 'min'.
 * @param {*} [value=0] - The constant value to use for imputation
 *   when using method 'value'.
 */
function Impute(params) {
  Transform.call(this, [], params);
}

Impute.Definition = {
  "type": "Impute",
  "metadata": {"changes": true},
  "params": [
    { "name": "field", "type": "field", "required": true },
    { "name": "key", "type": "field", "required": true },
    { "name": "keyvals", "array": true },
    { "name": "groupby", "type": "field", "array": true },
    { "name": "method", "type": "enum", "default": "value",
      "values": ["value", "mean", "median", "max", "min"] },
    { "name": "value", "default": 0 }
  ]
};

var prototype$n = inherits(Impute, Transform);

function getValue(_) {
  var m = _.method || Methods.value, v;

  if (Methods[m] == null) {
    error('Unrecognized imputation method: ' + m);
  } else if (m === Methods.value) {
    v = _.value !== undefined ? _.value : 0;
    return function() { return v; };
  } else {
    return Methods[m];
  }
}

function getField(_) {
  var f = _.field;
  return function(t) { return t ? f(t) : NaN; };
}

prototype$n.transform = function(_, pulse) {
  var out = pulse.fork(pulse.ALL),
      impute = getValue(_),
      field = getField(_),
      fName = accessorName(_.field),
      kName = accessorName(_.key),
      gNames = (_.groupby || []).map(accessorName),
      groups = partition$1(pulse.source, _.groupby, _.key, _.keyvals),
      curr = [],
      prev = this.value,
      m = groups.domain.length,
      group, value, gVals, kVal, g, i, j, l, n, t;

  for (g=0, l=groups.length; g<l; ++g) {
    group = groups[g];
    gVals = group.values;
    value = NaN;

    // add tuples for missing values
    for (j=0; j<m; ++j) {
      if (group[j] != null) continue;
      kVal = groups.domain[j];

      t = {_impute: true};
      for (i=0, n=gVals.length; i<n; ++i) t[gNames[i]] = gVals[i];
      t[kName] = kVal;
      t[fName] = Number.isNaN(value) ? (value = impute(group, field)) : value;

      curr.push(ingest(t));
    }
  }

  // update pulse with imputed tuples
  if (curr.length) out.add = out.materialize(out.ADD).add.concat(curr);
  if (prev.length) out.rem = out.materialize(out.REM).rem.concat(prev);
  this.value = curr;

  return out;
};

function partition$1(data, groupby, key, keyvals) {
  var get = function(f) { return f(t); },
      groups = [],
      domain = keyvals ? keyvals.slice() : [],
      kMap = {},
      gMap = {}, gVals, gKey,
      group, i, j, k, n, t;

  domain.forEach(function(k, i) { kMap[k] = i + 1; });

  for (i=0, n=data.length; i<n; ++i) {
    t = data[i];
    k = key(t);
    j = kMap[k] || (kMap[k] = domain.push(k));

    gKey = (gVals = groupby ? groupby.map(get) : Empty) + '';
    if (!(group = gMap[gKey])) {
      group = (gMap[gKey] = []);
      groups.push(group);
      group.values = gVals;
    }
    group[j-1] = t;
  }

  groups.domain = domain;
  return groups;
}

/**
 * Extend input tuples with aggregate values.
 * Calcuates aggregate values and joins them with the input stream.
 * @constructor
 */
function JoinAggregate(params) {
  Aggregate.call(this, params);
}

JoinAggregate.Definition = {
  "type": "JoinAggregate",
  "metadata": {"modifies": true},
  "params": [
    { "name": "groupby", "type": "field", "array": true },
    { "name": "fields", "type": "field", "null": true, "array": true },
    { "name": "ops", "type": "enum", "array": true, "values": ValidAggregateOps },
    { "name": "as", "type": "string", "null": true, "array": true },
    { "name": "key", "type": "field" }
  ]
};

var prototype$o = inherits(JoinAggregate, Aggregate);

prototype$o.transform = function(_, pulse) {
  var aggr = this,
      mod = _.modified(),
      cells;

  // process all input tuples to calculate aggregates
  if (aggr.value && (mod || pulse.modified(aggr._inputs, true))) {
    cells = aggr.value = mod ? aggr.init(_) : {};
    pulse.visit(pulse.SOURCE, function(t) { aggr.add(t); });
  } else {
    cells = aggr.value = aggr.value || this.init(_);
    pulse.visit(pulse.REM, function(t) { aggr.rem(t); });
    pulse.visit(pulse.ADD, function(t) { aggr.add(t); });
  }

  // update aggregation cells
  aggr.changes();

  // write aggregate values to input tuples
  pulse.visit(pulse.SOURCE, function(t) {
    extend(t, cells[aggr.cellkey(t)].tuple);
  });

  return pulse.reflow(mod).modifies(this._outputs);
};

prototype$o.changes = function() {
  var adds = this._adds,
      mods = this._mods,
      i, n;

  for (i=0, n=this._alen; i<n; ++i) {
    this.celltuple(adds[i]);
    adds[i] = null; // for garbage collection
  }

  for (i=0, n=this._mlen; i<n; ++i) {
    this.celltuple(mods[i]);
    mods[i] = null; // for garbage collection
  }

  this._alen = this._mlen = 0; // reset list of active cells
};

/**
 * Compute kernel density estimates (KDE) for one or more data groups.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors
 *   to groupby.
 * @param {function(object): *} params.field - An accessor for the data field
 *   to estimate.
 * @param {number} [params.bandwidth=0] - The KDE kernel bandwidth.
 *   If zero or unspecified, the bandwidth is automatically determined.
 * @param {boolean} [params.counts=false] - A boolean flag indicating if the
 *   output values should be probability estimates (false, default) or
 *   smoothed counts (true).
 * @param {string} [params.cumulative=false] - A boolean flag indicating if a
 *   density (false) or cumulative distribution (true) should be generated.
 * @param {Array<number>} [params.extent] - The domain extent over which to
 *   plot the density. If unspecified, the [min, max] data extent is used.
 * @param {string} [params.resolve='independent'] - Indicates how parameters for
 *   multiple densities should be resolved. If "independent" (the default), each
 *   density may have its own domain extent and dynamic number of curve sample
 *   steps. If "shared", the KDE transform will ensure that all densities are
 *   defined over a shared domain and curve steps, enabling stacking.
 * @param {number} [params.minsteps=25] - The minimum number of curve samples
 *   for plotting the density.
 * @param {number} [params.maxsteps=200] - The maximum number of curve samples
 *   for plotting the density.
 * @param {number} [params.steps] - The exact number of curve samples for
 *   plotting the density. If specified, overrides both minsteps and maxsteps
 *   to set an exact number of uniform samples. Useful in conjunction with
 *   a fixed extent to ensure consistent sample points for stacked densities.
 */
function KDE(params) {
  Transform.call(this, null, params);
}

KDE.Definition = {
  "type": "KDE",
  "metadata": {"generates": true},
  "params": [
    { "name": "groupby", "type": "field", "array": true },
    { "name": "field", "type": "field", "required": true },
    { "name": "cumulative", "type": "boolean", "default": false },
    { "name": "counts", "type": "boolean", "default": false },
    { "name": "bandwidth", "type": "number", "default": 0 },
    { "name": "extent", "type": "number", "array": true, "length": 2 },
    { "name": "resolve", "type": "enum", "values": ["shared", "independent"], "default": "independent" },
    { "name": "steps", "type": "number" },
    { "name": "minsteps", "type": "number", "default": 25 },
    { "name": "maxsteps", "type": "number", "default": 200 },
    { "name": "as", "type": "string", "array": true, "default": ["value", "density"] }
  ]
};

var prototype$p = inherits(KDE, Transform);

prototype$p.transform = function(_, pulse) {
  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS);

  if (!this.value || pulse.changed() || _.modified()) {
    const source = pulse.materialize(pulse.SOURCE).source,
          groups = partition(source, _.groupby, _.field),
          names = (_.groupby || []).map(accessorName),
          bandwidth = _.bandwidth,
          method = _.cumulative ? 'cdf' : 'pdf',
          as = _.as || ['value', 'density'],
          values = [];

    let domain = _.extent,
        minsteps = _.steps || _.minsteps || 25,
        maxsteps = _.steps || _.maxsteps || 200;

    if (method !== 'pdf' && method !== 'cdf') {
      error('Invalid density method: ' + method);
    }

    if (_.resolve === 'shared') {
      if (!domain) domain = extent(source, _.field);
      minsteps = maxsteps = _.steps || maxsteps;
    }

    groups.forEach(g => {
      const density = randomKDE(g, bandwidth)[method],
            scale = _.counts ? g.length : 1,
            local = domain || extent(g);

      sampleCurve(density, local, minsteps, maxsteps).forEach(v => {
        const t = {};
        for (let i=0; i<names.length; ++i) {
          t[names[i]] = g.dims[i];
        }
        t[as[0]] = v[0];
        t[as[1]] = v[1] * scale;
        values.push(ingest(t));
      });
    });

    if (this.value) out.rem = this.value;
    this.value = out.add = out.source = values;
  }

  return out;
};

/**
 * Generates a key function.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<string>} params.fields - The field name(s) for the key function.
 * @param {boolean} params.flat - A boolean flag indicating if the field names
 *  should be treated as flat property names, side-stepping nested field
 *  lookups normally indicated by dot or bracket notation.
 */
function Key(params) {
  Operator.call(this, null, update$4, params);
}

inherits(Key, Operator);

function update$4(_) {
  return (this.value && !_.modified()) ? this.value : key(_.fields, _.flat);
}

/**
 * Load and parse data from an external source. Marshalls parameter
 * values and then invokes the Dataflow request method.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {string} params.url - The URL to load from.
 * @param {object} params.format - The data format options.
 */
function Load(params) {
  Transform.call(this, [], params);
  this._pending = null;
}

var prototype$q = inherits(Load, Transform);

prototype$q.transform = function(_, pulse) {
  const df = pulse.dataflow;

  if (this._pending) {
    // update state and return pulse
    return output$1(this, pulse, this._pending);
  }

  if (stop(_)) return pulse.StopPropagation;

  if (_.values) {
    // parse and ingest values, return output pulse
    return output$1(this, pulse, df.parse(_.values, _.format));
  } else if (_.async) {
    // return promise for non-blocking async loading
    const p = df.request(_.url, _.format).then(res => {
      this._pending = array(res.data);
      return df => df.touch(this);
    });
    return {async: p};
  } else {
    // return promise for synchronous loading
    return df.request(_.url, _.format)
      .then(res => output$1(this, pulse, array(res.data)));
  }
};

function stop(_) {
  return _.modified('async') && !(
    _.modified('values') || _.modified('url') || _.modified('format')
  );
}

function output$1(op, pulse, data) {
  data.forEach(ingest);
  const out = pulse.fork(pulse.NO_FIELDS & pulse.NO_SOURCE);
  out.rem = op.value;
  op.value = out.source = out.add = data;
  op._pending = null;
  return out;
}

/**
 * Extend tuples by joining them with values from a lookup table.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Map} params.index - The lookup table map.
 * @param {Array<function(object): *} params.fields - The fields to lookup.
 * @param {Array<string>} params.as - Output field names for each lookup value.
 * @param {*} [params.default] - A default value to use if lookup fails.
 */
function Lookup(params) {
  Transform.call(this, {}, params);
}

Lookup.Definition = {
  "type": "Lookup",
  "metadata": {"modifies": true},
  "params": [
    { "name": "index", "type": "index", "params": [
        {"name": "from", "type": "data", "required": true },
        {"name": "key", "type": "field", "required": true }
      ] },
    { "name": "values", "type": "field", "array": true },
    { "name": "fields", "type": "field", "array": true, "required": true },
    { "name": "as", "type": "string", "array": true },
    { "name": "default", "default": null }
  ]
};

var prototype$r = inherits(Lookup, Transform);

prototype$r.transform = function(_, pulse) {
  var out = pulse,
      as = _.as,
      keys = _.fields,
      index = _.index,
      values = _.values,
      defaultValue = _.default==null ? null : _.default,
      reset = _.modified(),
      flag = reset ? pulse.SOURCE : pulse.ADD,
      n = keys.length,
      set, m, mods;

  if (values) {
    m = values.length;

    if (n > 1 && !as) {
      error('Multi-field lookup requires explicit "as" parameter.');
    }
    if (as && as.length !== n * m) {
      error('The "as" parameter has too few output field names.');
    }
    as = as || values.map(accessorName);

    set = function(t) {
      for (var i=0, k=0, j, v; i<n; ++i) {
        v = index.get(keys[i](t));
        if (v == null) for (j=0; j<m; ++j, ++k) t[as[k]] = defaultValue;
        else for (j=0; j<m; ++j, ++k) t[as[k]] = values[j](v);
      }
    };
  } else {
    if (!as) {
      error('Missing output field names.');
    }

    set = function(t) {
      for (var i=0, v; i<n; ++i) {
        v = index.get(keys[i](t));
        t[as[i]] = v==null ? defaultValue : v;
      }
    };
  }

  if (reset) {
    out = pulse.reflow(true);
  } else {
    mods = keys.some(function(k) { return pulse.modified(k.fields); });
    flag |= (mods ? pulse.MOD : 0);
  }
  pulse.visit(flag, set);

  return out.modifies(as);
};

/**
 * Computes global min/max extents over a collection of extents.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<Array<number>>} params.extents - The input extents.
 */
function MultiExtent(params) {
  Operator.call(this, null, update$5, params);
}

inherits(MultiExtent, Operator);

function update$5(_) {
  if (this.value && !_.modified()) {
    return this.value;
  }

  var min = +Infinity,
      max = -Infinity,
      ext = _.extents,
      i, n, e;

  for (i=0, n=ext.length; i<n; ++i) {
    e = ext[i];
    if (e[0] < min) min = e[0];
    if (e[1] > max) max = e[1];
  }
  return [min, max];
}

/**
 * Merge a collection of value arrays.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<Array<*>>} params.values - The input value arrrays.
 */
function MultiValues(params) {
  Operator.call(this, null, update$6, params);
}

inherits(MultiValues, Operator);

function update$6(_) {
  return (this.value && !_.modified())
    ? this.value
    : _.values.reduce(function(data, _) { return data.concat(_); }, []);
}

/**
 * Operator whose value is simply its parameter hash. This operator is
 * useful for enabling reactive updates to values of nested objects.
 * @constructor
 * @param {object} params - The parameters for this operator.
 */
function Params(params) {
  Transform.call(this, null, params);
}

inherits(Params, Transform);

Params.prototype.transform = function(_, pulse) {
  this.modified(_.modified());
  this.value = _;
  return pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS); // do not pass tuples
};

/**
 * Aggregate and pivot selected field values to become new fields.
 * This operator is useful to construction cross-tabulations.
 * @constructor
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors
 *  to groupby. These fields act just like groupby fields of an Aggregate transform.
 * @param {function(object): *} params.field - The field to pivot on. The unique
 *  values of this field become new field names in the output stream.
 * @param {function(object): *} params.value - The field to populate pivoted fields.
 *  The aggregate values of this field become the values of the new pivoted fields.
 * @param {string} [params.op] - The aggregation operation for the value field,
 *  applied per cell in the output stream. The default is "sum".
 * @param {number} [params.limit] - An optional parameter indicating the maximum
 *  number of pivoted fields to generate. The pivoted field names are sorted in
 *  ascending order prior to enforcing the limit.
 */
function Pivot(params) {
  Aggregate.call(this, params);
}

Pivot.Definition = {
  "type": "Pivot",
  "metadata": {"generates": true, "changes": true},
  "params": [
    { "name": "groupby", "type": "field", "array": true },
    { "name": "field", "type": "field", "required": true },
    { "name": "value", "type": "field", "required": true },
    { "name": "op", "type": "enum", "values": ValidAggregateOps, "default": "sum" },
    { "name": "limit", "type": "number", "default": 0 },
    { "name": "key", "type": "field" }
  ]
};

var prototype$s = inherits(Pivot, Aggregate);

prototype$s._transform = prototype$s.transform;

prototype$s.transform = function(_, pulse) {
  return this._transform(aggregateParams(_, pulse), pulse);
};

// Shoehorn a pivot transform into an aggregate transform!
// First collect all unique pivot field values.
// Then generate aggregate fields for each output pivot field.
function aggregateParams(_, pulse) {
  var key    = _.field,
      value  = _.value,
      op     = (_.op === 'count' ? '__count__' : _.op) || 'sum',
      fields = accessorFields(key).concat(accessorFields(value)),
      keys   = pivotKeys(key, _.limit || 0, pulse);

  // if data stream content changes, pivot fields may change
  // flag parameter modification to ensure re-initialization
  if (pulse.changed()) _.set('__pivot__', null, null, true);

  return {
    key:      _.key,
    groupby:  _.groupby,
    ops:      keys.map(function() { return op; }),
    fields:   keys.map(function(k) { return get(k, key, value, fields); }),
    as:       keys.map(function(k) { return k + ''; }),
    modified: _.modified.bind(_)
  };
}

// Generate aggregate field accessor.
// Output NaN for non-existent values; aggregator will ignore!
function get(k, key, value, fields) {
  return accessor(
    function(d) { return key(d) === k ? value(d) : NaN; },
    fields,
    k + ''
  );
}

// Collect (and optionally limit) all unique pivot values.
function pivotKeys(key, limit, pulse) {
  var map = {},
      list = [];

  pulse.visit(pulse.SOURCE, function(t) {
    var k = key(t);
    if (!map[k]) {
      map[k] = 1;
      list.push(k);
    }
  });

  // TODO? Move this comparator to vega-util?
  list.sort(function(u, v) {
    return (u<v||u==null) && v!=null ? -1
      : (u>v||v==null) && u!=null ? 1
      : ((v=v instanceof Date?+v:v),(u=u instanceof Date?+u:u))!==u && v===v ? -1
      : v!==v && u===u ? 1 : 0;
  });

  return limit ? list.slice(0, limit) : list;
}

/**
 * Partitions pre-faceted data into tuple subflows.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(Dataflow, string): Operator} params.subflow - A function
 *   that generates a subflow of operators and returns its root operator.
 * @param {function(object): Array<object>} params.field - The field
 *   accessor for an array of subflow tuple objects.
 */
function PreFacet(params) {
  Facet.call(this, params);
}

var prototype$t = inherits(PreFacet, Facet);

prototype$t.transform = function(_, pulse) {
  var self = this,
      flow = _.subflow,
      field = _.field;

  if (_.modified('field') || field && pulse.modified(accessorFields(field))) {
    error('PreFacet does not support field modification.');
  }

  this._targets.active = 0; // reset list of active subflows

  pulse.visit(pulse.MOD, function(t) {
    var sf = self.subflow(tupleid(t), flow, pulse, t);
    field ? field(t).forEach(function(_) { sf.mod(_); }) : sf.mod(t);
  });

  pulse.visit(pulse.ADD, function(t) {
    var sf = self.subflow(tupleid(t), flow, pulse, t);
    field ? field(t).forEach(function(_) { sf.add(ingest(_)); }) : sf.add(t);
  });

  pulse.visit(pulse.REM, function(t) {
    var sf = self.subflow(tupleid(t), flow, pulse, t);
    field ? field(t).forEach(function(_) { sf.rem(_); }) : sf.rem(t);
  });

  return pulse;
};

/**
 * Performs a relational projection, copying selected fields from source
 * tuples to a new set of derived tuples.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<function(object): *} params.fields - The fields to project,
 *   as an array of field accessors. If unspecified, all fields will be
 *   copied with names unchanged.
 * @param {Array<string>} [params.as] - Output field names for each projected
 *   field. Any unspecified fields will use the field name provided by
 *   the field accessor.
 */
function Project(params) {
  Transform.call(this, null, params);
}

Project.Definition = {
  "type": "Project",
  "metadata": {"generates": true, "changes": true},
  "params": [
    { "name": "fields", "type": "field", "array": true },
    { "name": "as", "type": "string", "null": true, "array": true }
  ]
};

var prototype$u = inherits(Project, Transform);

prototype$u.transform = function(_, pulse) {
  var fields = _.fields,
      as = fieldNames(_.fields, _.as || []),
      derive = fields
        ? function(s, t) { return project(s, t, fields, as); }
        : rederive,
      out, lut;

  if (this.value) {
    lut = this.value;
  } else {
    pulse = pulse.addAll();
    lut = this.value = {};
  }

  out = pulse.fork(pulse.NO_SOURCE);

  pulse.visit(pulse.REM, function(t) {
    var id = tupleid(t);
    out.rem.push(lut[id]);
    lut[id] = null;
  });

  pulse.visit(pulse.ADD, function(t) {
    var dt = derive(t, ingest({}));
    lut[tupleid(t)] = dt;
    out.add.push(dt);
  });

  pulse.visit(pulse.MOD, function(t) {
    out.mod.push(derive(t, lut[tupleid(t)]));
  });

  return out;
};

function project(s, t, fields, as) {
  for (var i=0, n=fields.length; i<n; ++i) {
    t[as[i]] = fields[i](s);
  }
  return t;
}

/**
 * Proxy the value of another operator as a pure signal value.
 * Ensures no tuples are propagated.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {*} params.value - The value to proxy, becomes the value of this operator.
 */
function Proxy(params) {
  Transform.call(this, null, params);
}

var prototype$v = inherits(Proxy, Transform);

prototype$v.transform = function(_, pulse) {
  this.value = _.value;
  return _.modified('value')
    ? pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS)
    : pulse.StopPropagation;
};

/**
 * Generates sample quantile values from an input data stream.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - An accessor for the data field
 *   over which to calculate quantile values.
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors
 *   to groupby.
 * @param {Array<number>} [params.probs] - An array of probabilities in
 *   the range (0, 1) for which to compute quantile values. If not specified,
 *   the *step* parameter will be used.
 * @param {Array<number>} [params.step=0.01] - A probability step size for
 *   sampling quantile values. All values from one-half the step size up to
 *   1 (exclusive) will be sampled. This parameter is only used if the
 *   *quantiles* parameter is not provided.
 */
function Quantile(params) {
  Transform.call(this, null, params);
}

Quantile.Definition = {
  "type": "Quantile",
  "metadata": {"generates": true, "changes": true},
  "params": [
    { "name": "groupby", "type": "field", "array": true },
    { "name": "field", "type": "field", "required": true },
    { "name": "probs", "type": "number", "array": true },
    { "name": "step", "type": "number", "default": 0.01 },
    { "name": "as", "type": "string", "array": true, "default": ["prob", "value"] }
  ]
};

var prototype$w = inherits(Quantile, Transform);

var EPSILON$1 = 1e-14;

prototype$w.transform = function(_, pulse) {
  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS),
      as = _.as || ['prob', 'value'];

  if (this.value && !_.modified() && !pulse.changed()) {
    out.source = this.value;
    return out;
  }

  const source = pulse.materialize(pulse.SOURCE).source,
        groups = partition(source, _.groupby, _.field),
        names = (_.groupby || []).map(accessorName),
        values = [],
        step = _.step || 0.01,
        p = _.probs || sequence(step/2, 1 - EPSILON$1, step),
        n = p.length;

  groups.forEach(g => {
    const q = quantiles(g, p);

    for (let i=0; i<n; ++i) {
      const t = {};
      for (let i=0; i<names.length; ++i) {
        t[names[i]] = g.dims[i];
      }
      t[as[0]] = p[i];
      t[as[1]] = q[i];
      values.push(ingest(t));
    }
  });

  if (this.value) out.rem = this.value;
  this.value = out.add = out.source = values;

  return out;
};

/**
 * Relays a data stream between data processing pipelines.
 * If the derive parameter is set, this transform will create derived
 * copies of observed tuples. This provides derived data streams in which
 * modifications to the tuples do not pollute an upstream data source.
 * @param {object} params - The parameters for this operator.
 * @param {number} [params.derive=false] - Boolean flag indicating if
 *   the transform should make derived copies of incoming tuples.
 * @constructor
 */
function Relay(params) {
  Transform.call(this, null, params);
}

var prototype$x = inherits(Relay, Transform);

prototype$x.transform = function(_, pulse) {
  var out, lut;

  if (this.value) {
    lut = this.value;
  } else {
    out = pulse = pulse.addAll();
    lut = this.value = {};
  }

  if (_.derive) {
    out = pulse.fork(pulse.NO_SOURCE);

    pulse.visit(pulse.REM, t => {
      var id = tupleid(t);
      out.rem.push(lut[id]);
      lut[id] = null;
    });

    pulse.visit(pulse.ADD, t => {
      var dt = derive(t);
      lut[tupleid(t)] = dt;
      out.add.push(dt);
    });

    pulse.visit(pulse.MOD, t => {
      var dt = lut[tupleid(t)], k;
      for (k in t) {
        dt[k] = t[k];
        // down stream writes may overwrite re-derived tuples
        // conservatively mark all source fields as modified
        out.modifies(k);
      }
      out.mod.push(dt);
    });
  }

  return out;
};

/**
 * Samples tuples passing through this operator.
 * Uses reservoir sampling to maintain a representative sample.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {number} [params.size=1000] - The maximum number of samples.
 */
function Sample(params) {
  Transform.call(this, [], params);
  this.count = 0;
}

Sample.Definition = {
  "type": "Sample",
  "metadata": {},
  "params": [
    { "name": "size", "type": "number", "default": 1000 }
  ]
};

var prototype$y = inherits(Sample, Transform);

prototype$y.transform = function(_, pulse) {
  var out = pulse.fork(pulse.NO_SOURCE),
      mod = _.modified('size'),
      num = _.size,
      res = this.value,
      cnt = this.count,
      cap = 0,
      map = res.reduce(function(m, t) {
        m[tupleid(t)] = 1;
        return m;
      }, {});

  // sample reservoir update function
  function update(t) {
    var p, idx;

    if (res.length < num) {
      res.push(t);
    } else {
      idx = ~~((cnt + 1) * random());
      if (idx < res.length && idx >= cap) {
        p = res[idx];
        if (map[tupleid(p)]) out.rem.push(p); // eviction
        res[idx] = t;
      }
    }
    ++cnt;
  }

  if (pulse.rem.length) {
    // find all tuples that should be removed, add to output
    pulse.visit(pulse.REM, function(t) {
      var id = tupleid(t);
      if (map[id]) {
        map[id] = -1;
        out.rem.push(t);
      }
      --cnt;
    });

    // filter removed tuples out of the sample reservoir
    res = res.filter(function(t) { return map[tupleid(t)] !== -1; });
  }

  if ((pulse.rem.length || mod) && res.length < num && pulse.source) {
    // replenish sample if backing data source is available
    cap = cnt = res.length;
    pulse.visit(pulse.SOURCE, function(t) {
      // update, but skip previously sampled tuples
      if (!map[tupleid(t)]) update(t);
    });
    cap = -1;
  }

  if (mod && res.length > num) {
    for (var i=0, n=res.length-num; i<n; ++i) {
      map[tupleid(res[i])] = -1;
      out.rem.push(res[i]);
    }
    res = res.slice(n);
  }

  if (pulse.mod.length) {
    // propagate modified tuples in the sample reservoir
    pulse.visit(pulse.MOD, function(t) {
      if (map[tupleid(t)]) out.mod.push(t);
    });
  }

  if (pulse.add.length) {
    // update sample reservoir
    pulse.visit(pulse.ADD, update);
  }

  if (pulse.add.length || cap < 0) {
    // output newly added tuples
    out.add = res.filter(function(t) { return !map[tupleid(t)]; });
  }

  this.count = cnt;
  this.value = out.source = res;
  return out;
};

/**
 * Generates data tuples for a specified sequence range of numbers.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {number} params.start - The first number in the sequence.
 * @param {number} params.stop - The last number (exclusive) in the sequence.
 * @param {number} [params.step=1] - The step size between numbers in the sequence.
 */
function Sequence(params) {
  Transform.call(this, null, params);
}

Sequence.Definition = {
  "type": "Sequence",
  "metadata": {"generates": true, "changes": true},
  "params": [
    { "name": "start", "type": "number", "required": true },
    { "name": "stop", "type": "number", "required": true },
    { "name": "step", "type": "number", "default": 1 },
    { "name": "as", "type": "string", "default": "data" }
  ]
};

var prototype$z = inherits(Sequence, Transform);

prototype$z.transform = function(_, pulse) {
  if (this.value && !_.modified()) return;

  var out = pulse.materialize().fork(pulse.MOD),
      as = _.as || 'data';

  out.rem = this.value ? pulse.rem.concat(this.value) : pulse.rem;

  this.value = sequence(_.start, _.stop, _.step || 1).map(function(v) {
    var t = {};
    t[as] = v;
    return ingest(t);
  });

  out.add = pulse.add.concat(this.value);

  return out;
};

/**
 * Propagates a new pulse without any tuples so long as the input
 * pulse contains some added, removed or modified tuples.
 * @param {object} params - The parameters for this operator.
 * @constructor
 */
function Sieve(params) {
  Transform.call(this, null, params);
  this.modified(true); // always treat as modified
}

var prototype$A = inherits(Sieve, Transform);

prototype$A.transform = function(_, pulse) {
  this.value = pulse.source;
  return pulse.changed()
    ? pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS)
    : pulse.StopPropagation;
};

const YEAR = 'year';
const QUARTER = 'quarter';
const MONTH = 'month';
const WEEK = 'week';
const DATE = 'date';
const DAY = 'day';
const HOURS = 'hours';
const MINUTES = 'minutes';
const SECONDS = 'seconds';
const MILLISECONDS = 'milliseconds';

const UNITS = [
  YEAR,
  QUARTER,
  MONTH,
  WEEK,
  DATE,
  DAY,
  HOURS,
  MINUTES,
  SECONDS,
  MILLISECONDS
].reduce((o, u, i) => (o[u] = 1 + i, o), {});

function timeUnits(units) {
  const u = array(units).slice(),
        m = {};

  // check validity
  if (!u.length) error('Missing time unit.');

  u.forEach(unit => {
    if (hasOwnProperty(UNITS, unit)) {
      m[unit] = 1;
    } else {
      error(`Invalid time unit: ${unit}.`);
    }
  });

  if ((m[WEEK] || m[DAY]) && (m[QUARTER] || m[MONTH] || m[DATE])) {
    error(`Incompatible time units: ${units}`);
  }

  // ensure proper sort order
  u.sort((a, b) => UNITS[a] - UNITS[b]);

  return u;
}

const t0 = new Date;

function floor(units, step, get, inv, newDate) {
  const s = step || 1,
        b = peek(units),
        _ = (unit, p, key) => {
          key = key || unit;
          return getUnit(get[key], inv[key], unit === b && s, p);
        };

  const t = new Date,
        u = toSet(units),
        y = u[YEAR] ? _(YEAR) : constant(2012),
        m = u[MONTH] ? _(MONTH)
          : u[QUARTER] ? _(QUARTER)
          : zero,
        d = u[WEEK] && u[DAY] ? _(DAY, 1, WEEK + DAY)
          : u[WEEK] ? _(WEEK, 1)
          : u[DAY] ? _(DAY, 1)
          : u[DATE] ? _(DATE, 1)
          : one,
        H = u[HOURS] ? _(HOURS) : zero,
        M = u[MINUTES] ? _(MINUTES) : zero,
        S = u[SECONDS] ? _(SECONDS) : zero,
        L = u[MILLISECONDS] ? _(MILLISECONDS) : zero;

  return function(v) {
    t.setTime(+v);
    const year = y(t);
    return newDate(year, m(t), d(t, year), H(t), M(t), S(t), L(t));
  };
}

function getUnit(f, inv, step, phase) {
  const u = step <= 1 ? f
    : phase ? (d, y) => phase + step * Math.floor((f(d, y) - phase) / step)
    : (d, y) => step * Math.floor(f(d, y) / step);
  return inv ? (d, y) => inv(u(d, y), y) : u;
}

// returns the day of the year based on week number, day of week,
// and the day of the week for the first day of the year
function weekday(week, day, firstDay) {
  return day + week * 7 - (firstDay + 6) % 7;
}

// -- LOCAL TIME --

const localGet = {
  [YEAR]:         d => d.getFullYear(),
  [QUARTER]:      d => Math.floor(d.getMonth() / 3),
  [MONTH]:        d => d.getMonth(),
  [DATE]:         d => d.getDate(),
  [HOURS]:        d => d.getHours(),
  [MINUTES]:      d => d.getMinutes(),
  [SECONDS]:      d => d.getSeconds(),
  [MILLISECONDS]: d => d.getMilliseconds(),
  [WEEK]:         d => localWeekNum(d),
  [WEEK + DAY]:   (d, y) => weekday(localWeekNum(d), d.getDay(), localFirst(y)),
  [DAY]:          (d, y) => weekday(1, d.getDay(), localFirst(y))
};

const localInv = {
  [QUARTER]: q => 3 * q,
  [WEEK]:    (w, y) => weekday(w, 0, localFirst(y))
};

function localYear(y) {
  t0.setFullYear(y);
  t0.setMonth(0);
  t0.setDate(1);
  t0.setHours(0, 0, 0, 0);
  return t0;
}

function localWeekNum(d) {
  return timeWeek.count(localYear(d.getFullYear()) - 1, d);
}

function localFirst(y) {
  return localYear(y).getDay();
}

function localDate(y, m, d, H, M, S, L) {
  if (0 <= y && y < 100) {
    var date = new Date(-1, m, d, H, M, S, L);
    date.setFullYear(y);
    return date;
  }
  return new Date(y, m, d, H, M, S, L);
}

function timeFloor(units, step) {
  return floor(units, step || 1, localGet, localInv, localDate);
}

// -- UTC TIME --

const utcGet = {
  [YEAR]:         d => d.getUTCFullYear(),
  [QUARTER]:      d => Math.floor(d.getUTCMonth() / 3),
  [MONTH]:        d => d.getUTCMonth(),
  [DATE]:         d => d.getUTCDate(),
  [HOURS]:        d => d.getUTCHours(),
  [MINUTES]:      d => d.getUTCMinutes(),
  [SECONDS]:      d => d.getUTCSeconds(),
  [MILLISECONDS]: d => d.getUTCMilliseconds(),
  [WEEK]:         d => utcWeekNum(d),
  [DAY]:          (d, y) => weekday(1, d.getUTCDay(), utcFirst(y)),
  [WEEK + DAY]:   (d, y) => weekday(utcWeekNum(d), d.getUTCDay(), utcFirst(y))
};

const utcInv = {
  [QUARTER]: q => 3 * q,
  [WEEK]:    (w, y) => weekday(w, 0, utcFirst(y))
};

function utcWeekNum(d) {
  const y = Date.UTC(d.getUTCFullYear(), 0, 1);
  return utcWeek.count(y - 1, d);
}

function utcFirst(y) {
  t0.setTime(Date.UTC(y, 0, 1));
  return t0.getUTCDay();
}

function utcDate(y, m, d, H, M, S, L) {
  if (0 <= y && y < 100) {
    var date = new Date(Date.UTC(-1, m, d, H, M, S, L));
    date.setUTCFullYear(d.y);
    return date;
  }
  return new Date(Date.UTC(y, m, d, H, M, S, L));
}

function utcFloor(units, step) {
  return floor(units, step || 1, utcGet, utcInv, utcDate);
}

const timeIntervals = {
  [YEAR]:         timeYear,
  [QUARTER]:      timeMonth.every(3),
  [MONTH]:        timeMonth,
  [WEEK]:         timeWeek,
  [DATE]:         timeDay,
  [DAY]:          timeDay,
  [HOURS]:        timeHour,
  [MINUTES]:      timeMinute,
  [SECONDS]:      timeSecond,
  [MILLISECONDS]: timeMillisecond
};

const utcIntervals = {
  [YEAR]:         utcYear,
  [QUARTER]:      utcMonth.every(3),
  [MONTH]:        utcMonth,
  [WEEK]:         utcWeek,
  [DATE]:         utcDay,
  [DAY]:          utcDay,
  [HOURS]:        utcHour,
  [MINUTES]:      utcMinute,
  [SECONDS]:      utcSecond,
  [MILLISECONDS]: utcMillisecond
};

function timeInterval(unit) {
  return timeIntervals[unit];
}

function utcInterval(unit) {
  return utcIntervals[unit];
}

function offset(ival, date, step) {
  return ival ? ival.offset(date, step) : undefined;
}

function timeOffset(unit, date, step) {
  return offset(timeInterval(unit), date, step);
}

function utcOffset(unit, date, step) {
  return offset(utcInterval(unit), date, step);
}

function sequence$1(ival, start, stop, step) {
  return ival ? ival.range(start, stop, step) : undefined;
}

function timeSequence(unit, start, stop, step) {
  return sequence$1(timeInterval(unit), start, stop, step);
}

function utcSequence(unit, start, stop, step) {
  return sequence$1(utcInterval(unit), start, stop, step);
}

const defaultSpecifiers = {
  [YEAR]: '%Y ',
  [QUARTER]: 'Q%q ',
  [MONTH]: '%b ',
  [DATE]: '%d ',
  [WEEK]: 'W%U ',
  [DAY]: '%a ',
  [HOURS]: '%H:00',
  [MINUTES]: '00:%M',
  [SECONDS]: ':%S',
  [MILLISECONDS]: '.%L',
  [`${YEAR}-${MONTH}`]: '%Y-%m ',
  [`${YEAR}-${MONTH}-${DATE}`]: '%Y-%m-%d ',
  [`${HOURS}-${MINUTES}`]: '%H:%M'
};

function timeUnitSpecifier(units, specifiers) {
  const s = extend({}, defaultSpecifiers, specifiers),
        u = timeUnits(units),
        n = u.length;

  let fmt = '', start = 0, end, key;

  for (start=0; start<n; ) {
    for (end=u.length; end > start; --end) {
      key = u.slice(start, end).join('-');
      if (s[key] != null) {
        fmt += s[key];
        start = end;
        break;
      }
    }
  }

  return fmt.trim();
}

function timeFormat(specifier) {
  return formatter(timeFormat$2, timeInterval, specifier);
}

function utcFormat(specifier) {
  return formatter(utcFormat$2, utcInterval, specifier);
}

function formatter(format, interval, specifier) {
  return isString(specifier)
    ? format(specifier)
    : multiFormat(format, interval, specifier);
}

function multiFormat(format, interval, spec) {
  spec = spec || {};
  if (!isObject(spec)) {
    error(`Invalid time multi-format specifier: ${spec}`);
  }

  const second = interval(SECONDS),
        minute = interval(MINUTES),
        hour = interval(HOURS),
        day = interval(DATE),
        week = interval(WEEK),
        month = interval(MONTH),
        quarter = interval(QUARTER),
        year = interval(YEAR),
        L = format(spec[MILLISECONDS] || '.%L'),
        S = format(spec[SECONDS] || ':%S'),
        M = format(spec[MINUTES] || '%I:%M'),
        H = format(spec[HOURS] || '%I %p'),
        d = format(spec[DATE] || spec[DAY] || '%a %d'),
        w = format(spec[WEEK] || '%b %d'),
        m = format(spec[MONTH] || '%B'),
        q = format(spec[QUARTER] || '%B'),
        y = format(spec[YEAR] || '%Y');

  return function(date) {
    return (second(date) < date ? L
      : minute(date) < date ? S
      : hour(date) < date ? M
      : day(date) < date ? H
      : month(date) < date ? (week(date) < date ? d : w)
      : year(date) < date ? (quarter(date) < date ? m : q)
      : y)(date);
  };
}

const durationSecond = 1000,
      durationMinute = durationSecond * 60,
      durationHour = durationMinute * 60,
      durationDay = durationHour * 24,
      durationWeek = durationDay * 7,
      durationMonth = durationDay * 30,
      durationYear = durationDay * 365;

const Milli   = [YEAR, MONTH, DATE, HOURS, MINUTES, SECONDS, MILLISECONDS],
      Seconds = Milli.slice(0, -1),
      Minutes = Seconds.slice(0, -1),
      Hours   = Minutes.slice(0, -1),
      Day     = Hours.slice(0, -1),
      Week    = [YEAR, WEEK],
      Month   = [YEAR, MONTH],
      Year    = [YEAR];

const intervals = [
  [Seconds,  1,      durationSecond],
  [Seconds,  5,  5 * durationSecond],
  [Seconds, 15, 15 * durationSecond],
  [Seconds, 30, 30 * durationSecond],
  [Minutes,  1,      durationMinute],
  [Minutes,  5,  5 * durationMinute],
  [Minutes, 15, 15 * durationMinute],
  [Minutes, 30, 30 * durationMinute],
  [  Hours,  1,      durationHour  ],
  [  Hours,  3,  3 * durationHour  ],
  [  Hours,  6,  6 * durationHour  ],
  [  Hours, 12, 12 * durationHour  ],
  [    Day,  1,      durationDay   ],
  [   Week,  1,      durationWeek  ],
  [  Month,  1,      durationMonth ],
  [  Month,  3,  3 * durationMonth ],
  [   Year,  1,      durationYear  ]
];

function timeBin(opt) {
  const ext = opt.extent,
        max = opt.maxbins || 40,
        target = Math.abs(span(ext)) / max;

  let i = bisector(i => i[2]).right(intervals, target),
      units, step;

  if (i === intervals.length) {
    units = Year,
    step = tickStep(ext[0] / durationYear, ext[1] / durationYear, max);
  } else if (i) {
    i = intervals[target / intervals[i - 1][2] < intervals[i][2] / target ? i - 1 : i];
    units = i[0];
    step = i[1];
  } else {
    units = Milli;
    step = Math.max(tickStep(ext[0], ext[1], max), 1);
  }

  return {units, step};
}

/**
 * Discretize dates to specific time units.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The data field containing date/time values.
 */
function TimeUnit(params) {
  Transform.call(this, null, params);
}

const OUTPUT = ['unit0', 'unit1'];

TimeUnit.Definition = {
  "type": "TimeUnit",
  "metadata": {"modifies": true},
  "params": [
    { "name": "field", "type": "field", "required": true },
    { "name": "interval", "type": "boolean", "default": true },
    { "name": "units", "type": "string", "array": true },
    { "name": "step", "type": "number", "default": 1 },
    { "name": "timezone", "type": "enum", "default": "local", "values": ["local", "utc"] },
    { "name": "as", "type": "string", "array": true, "length": 2, "default": OUTPUT }
  ]
};

var prototype$B = inherits(TimeUnit, Transform);

prototype$B.transform = function(_, pulse) {
  var field = _.field,
      band = _.interval !== false,
      utc = _.timezone === 'utc',
      floor = this._floor(_, pulse),
      offset = (utc ? utcInterval : timeInterval)(floor.unit).offset,
      as = _.as || OUTPUT,
      u0 = as[0],
      u1 = as[1],
      min = floor.start || Infinity,
      max = floor.stop || -Infinity,
      step = floor.step,
      flag = pulse.ADD;

  if (_.modified() || pulse.modified(accessorFields(_.field))) {
    pulse = pulse.reflow(true);
    flag = pulse.SOURCE;
    min = Infinity;
    max = -Infinity;
  }

  pulse.visit(flag, function(t) {
    var v = field(t), a, b;
    if (v == null) {
      t[u0] = null;
      if (band) t[u1] = null;
    } else {
      t[u0] = a = b = floor(v);
      if (band) t[u1] = b = offset(a, step);
      if (a < min) min = a;
      if (b > max) max = b;
    }
  });

  floor.start = min;
  floor.stop = max;

  return pulse.modifies(band ? as : u0);
};

prototype$B._floor = function(_, pulse) {
  const utc = _.timezone === 'utc';

  // get parameters
  let {units, step} = _.units
    ? {units: _.units, step: _.step || 1}
    : timeBin({
      extent:  extent(pulse.materialize(pulse.SOURCE).source, _.field),
      maxbins: _.maxbins
    });

  // check / standardize time units
  units = timeUnits(units);

  const prev = this.value || {},
        floor = (utc ? utcFloor : timeFloor)(units, step);

  floor.unit = peek(units);
  floor.units = units;
  floor.step = step;
  floor.start = prev.start;
  floor.stop = prev.stop;
  return this.value = floor;
};

/**
 * An index that maps from unique, string-coerced, field values to tuples.
 * Assumes that the field serves as a unique key with no duplicate values.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The field accessor to index.
 */
function TupleIndex(params) {
  Transform.call(this, fastmap(), params);
}

var prototype$C = inherits(TupleIndex, Transform);

prototype$C.transform = function(_, pulse) {
  var df = pulse.dataflow,
      field = _.field,
      index = this.value,
      mod = true;

  function set(t) { index.set(field(t), t); }

  if (_.modified('field') || pulse.modified(field.fields)) {
    index.clear();
    pulse.visit(pulse.SOURCE, set);
  } else if (pulse.changed()) {
    pulse.visit(pulse.REM, function(t) { index.delete(field(t)); });
    pulse.visit(pulse.ADD, set);
  } else {
    mod = false;
  }

  this.modified(mod);
  if (index.empty > df.cleanThreshold) df.runAfter(index.clean);
  return pulse.fork();
};

/**
 * Extracts an array of values. Assumes the source data has already been
 * reduced as needed (e.g., by an upstream Aggregate transform).
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The domain field to extract.
 * @param {function(*,*): number} [params.sort] - An optional
 *   comparator function for sorting the values. The comparator will be
 *   applied to backing tuples prior to value extraction.
 */
function Values(params) {
  Transform.call(this, null, params);
}

var prototype$D = inherits(Values, Transform);

prototype$D.transform = function(_, pulse) {
  var run = !this.value
    || _.modified('field')
    || _.modified('sort')
    || pulse.changed()
    || (_.sort && pulse.modified(_.sort.fields));

  if (run) {
    this.value = (_.sort
      ? pulse.source.slice().sort(stableCompare(_.sort))
      : pulse.source).map(_.field);
  }
};

function WindowOp(op, field, param, as) {
  let fn = WindowOps[op](field, param);
  return {
    init:   fn.init || zero,
    update: function(w, t) { t[as] = fn.next(w); }
  };
}

const WindowOps = {
  row_number: function() {
    return {
      next: w => w.index + 1
    };
  },
  rank: function() {
    let rank;
    return {
      init: () => rank = 1,
      next: w => {
        let i = w.index,
            data = w.data;
        return (i && w.compare(data[i - 1], data[i])) ? (rank = i + 1) : rank;
      }
    };
  },
  dense_rank: function() {
    let drank;
    return {
      init: () => drank = 1,
      next: w => {
        let i = w.index,
            d = w.data;
        return (i && w.compare(d[i - 1], d[i])) ? ++drank : drank;
      }
    };
  },
  percent_rank: function() {
    let rank = WindowOps.rank(),
        next = rank.next;
    return {
      init: rank.init,
      next: w => (next(w) - 1) / (w.data.length - 1)
    };
  },
  cume_dist: function() {
    let cume;
    return {
      init: () => cume = 0,
      next: w => {
        let i = w.index,
            d = w.data,
            c = w.compare;
        if (cume < i) {
          while (i + 1 < d.length && !c(d[i], d[i + 1])) ++i;
          cume = i;
        }
        return (1 + cume) / d.length;
      }
    };
  },
  ntile: function(field, num) {
    num = +num;
    if (!(num > 0)) error('ntile num must be greater than zero.');
    let cume = WindowOps.cume_dist(),
        next = cume.next;
    return {
      init: cume.init,
      next: w => Math.ceil(num * next(w))
    };
  },

  lag: function(field, offset) {
    offset = +offset || 1;
    return {
      next: w => {
        let i = w.index - offset;
        return i >= 0 ? field(w.data[i]) : null;
      }
    };
  },
  lead: function(field, offset) {
    offset = +offset || 1;
    return {
      next: w => {
        let i = w.index + offset,
            d = w.data;
        return i < d.length ? field(d[i]) : null;
      }
    };
  },

  first_value: function(field) {
    return {
      next: w => field(w.data[w.i0])
    };
  },
  last_value: function(field) {
    return {
      next: w => field(w.data[w.i1 - 1])
    }
  },
  nth_value: function(field, nth) {
    nth = +nth;
    if (!(nth > 0)) error('nth_value nth must be greater than zero.');
    return {
      next: w => {
        let i = w.i0 + (nth - 1);
        return i < w.i1 ? field(w.data[i]) : null;
      }
    }
  },

  prev_value: function(field) {
    let prev = null;
    return {
      next: w => {
        let v = field(w.data[w.index]);
        return v != null ? (prev = v) : prev;
      }
    }
  },
  next_value: function(field) {
    let v = null,
        i = -1;
    return {
      next: w => {
        let d = w.data;
        return w.index <= i ? v
          : (i = find(field, d, w.index)) < 0
            ? (i = d.length, v = null)
            : (v = field(d[i]));
      }
    };
  },

};

function find(field, data, index) {
  for (let n = data.length; index < n; ++index) {
    let v = field(data[index]);
    if (v != null) return index;
  }
  return -1;
}

var ValidWindowOps = Object.keys(WindowOps);

function WindowState(_) {
  let self = this,
      ops = array(_.ops),
      fields = array(_.fields),
      params = array(_.params),
      as = array(_.as),
      outputs = self.outputs = [],
      windows = self.windows = [],
      inputs = {},
      map = {},
      countOnly = true,
      counts = [],
      measures = [];

  function visitInputs(f) {
    array(accessorFields(f)).forEach(_ => inputs[_] = 1);
  }
  visitInputs(_.sort);

  ops.forEach(function(op, i) {
    let field = fields[i],
        mname = accessorName(field),
        name = measureName(op, mname, as[i]);

    visitInputs(field);
    outputs.push(name);

    // Window operation
    if (hasOwnProperty(WindowOps, op)) {
      windows.push(WindowOp(op, fields[i], params[i], name));
    }

    // Aggregate operation
    else {
      if (field == null && op !== 'count') {
        error('Null aggregate field specified.');
      }
      if (op === 'count') {
        counts.push(name);
        return;
      }

      countOnly = false;
      let m = map[mname];
      if (!m) {
        m = (map[mname] = []);
        m.field = field;
        measures.push(m);
      }
      m.push(createMeasure(op, name));
    }
  });

  if (counts.length || measures.length) {
    self.cell = cell(measures, counts, countOnly);
  }

  self.inputs = Object.keys(inputs);
}

const prototype$E = WindowState.prototype;

prototype$E.init = function() {
  this.windows.forEach(_ => _.init());
  if (this.cell) this.cell.init();
};

prototype$E.update = function(w, t) {
  let self = this,
      cell = self.cell,
      wind = self.windows,
      data = w.data,
      m = wind && wind.length,
      j;

  if (cell) {
    for (j=w.p0; j<w.i0; ++j) cell.rem(data[j]);
    for (j=w.p1; j<w.i1; ++j) cell.add(data[j]);
    cell.set(t);
  }
  for (j=0; j<m; ++j) wind[j].update(w, t);
};

function cell(measures, counts, countOnly) {
  measures = measures.map(m => compileMeasures(m, m.field));

  let cell = {
    num:   0,
    agg:   null,
    store: false,
    count: counts
  };

  if (!countOnly) {
    var n = measures.length,
        a = cell.agg = Array(n),
        i = 0;
    for (; i<n; ++i) a[i] = new measures[i](cell);
  }

  if (cell.store) {
    var store = cell.data = new TupleStore();
  }

  cell.add = function(t) {
    cell.num += 1;
    if (countOnly) return;
    if (store) store.add(t);
    for (let i=0; i<n; ++i) {
      a[i].add(a[i].get(t), t);
    }
  };

  cell.rem = function(t) {
    cell.num -= 1;
    if (countOnly) return;
    if (store) store.rem(t);
    for (let i=0; i<n; ++i) {
      a[i].rem(a[i].get(t), t);
    }
  };

  cell.set = function(t) {
    let i, n;

    // consolidate stored values
    if (store) store.values();

    // update tuple properties
    for (i=0, n=counts.length; i<n; ++i) t[counts[i]] = cell.num;
    if (!countOnly) for (i=0, n=a.length; i<n; ++i) a[i].set(t);
  };

  cell.init = function() {
    cell.num = 0;
    if (store) store.reset();
    for (let i=0; i<n; ++i) a[i].init();
  };

  return cell;
}

/**
 * Perform window calculations and write results to the input stream.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(*,*): number} [params.sort] - A comparator function for sorting tuples within a window.
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors by which to partition tuples into separate windows.
 * @param {Array<string>} params.ops - An array of strings indicating window operations to perform.
 * @param {Array<function(object): *>} [params.fields] - An array of accessors
 *   for data fields to use as inputs to window operations.
 * @param {Array<*>} [params.params] - An array of parameter values for window operations.
 * @param {Array<string>} [params.as] - An array of output field names for window operations.
 * @param {Array<number>} [params.frame] - Window frame definition as two-element array.
 * @param {boolean} [params.ignorePeers=false] - If true, base window frame boundaries on row
 *   number alone, ignoring peers with identical sort values. If false (default),
 *   the window boundaries will be adjusted to include peer values.
 */
function Window(params) {
  Transform.call(this, {}, params);
  this._mlen = 0;
  this._mods = [];
}

Window.Definition = {
  "type": "Window",
  "metadata": {"modifies": true},
  "params": [
    { "name": "sort", "type": "compare" },
    { "name": "groupby", "type": "field", "array": true },
    { "name": "ops", "type": "enum", "array": true, "values": ValidWindowOps.concat(ValidAggregateOps) },
    { "name": "params", "type": "number", "null": true, "array": true },
    { "name": "fields", "type": "field", "null": true, "array": true },
    { "name": "as", "type": "string", "null": true, "array": true },
    { "name": "frame", "type": "number", "null": true, "array": true, "length": 2, "default": [null, 0] },
    { "name": "ignorePeers", "type": "boolean", "default": false }
  ]
};

var prototype$F = inherits(Window, Transform);

prototype$F.transform = function(_, pulse) {
  var self = this,
      state = self.state,
      mod = _.modified(),
      cmp = stableCompare(_.sort),
      i, n;

  this.stamp = pulse.stamp;

  // initialize window state
  if (!state || mod) {
    state = self.state = new WindowState(_);
  }

  // retrieve group for a tuple
  var key = groupkey(_.groupby);
  function group(t) { return self.group(key(t)); }

  // partition input tuples
  if (mod || pulse.modified(state.inputs)) {
    self.value = {};
    pulse.visit(pulse.SOURCE, function(t) { group(t).add(t); });
  } else {
    pulse.visit(pulse.REM, function(t) { group(t).remove(t); });
    pulse.visit(pulse.ADD, function(t) { group(t).add(t); });
  }

  // perform window calculations for each modified partition
  for (i=0, n=self._mlen; i<n; ++i) {
    processPartition(self._mods[i], state, cmp, _);
  }
  self._mlen = 0;
  self._mods = [];

  // TODO don't reflow everything?
  return pulse.reflow(mod).modifies(state.outputs);
};

prototype$F.group = function(key) {
  var self = this,
      group = self.value[key];

  if (!group) {
    group = self.value[key] = SortedList(tupleid);
    group.stamp = -1;
  }

  if (group.stamp < self.stamp) {
    group.stamp = self.stamp;
    self._mods[self._mlen++] = group;
  }

  return group;
};

function processPartition(list, state, cmp, _) {
  var sort = _.sort,
      range = sort && !_.ignorePeers,
      frame = _.frame || [null, 0],
      data = list.data(cmp), // use cmp for stable sort
      n = data.length,
      i = 0,
      b = range ? bisector(sort) : null,
      w = {
        i0: 0, i1: 0, p0: 0, p1: 0, index: 0,
        data: data, compare: sort || constant(-1)
      };

  for (state.init(); i<n; ++i) {
    setWindow(w, frame, i, n);
    if (range) adjustRange(w, b);
    state.update(w, data[i]);
  }
}

function setWindow(w, f, i, n) {
  w.p0 = w.i0;
  w.p1 = w.i1;
  w.i0 = f[0] == null ? 0 : Math.max(0, i - Math.abs(f[0]));
  w.i1 = f[1] == null ? n : Math.min(n, i + Math.abs(f[1]) + 1);
  w.index = i;
}

// if frame type is 'range', adjust window for peer values
function adjustRange(w, bisect) {
  var r0 = w.i0,
      r1 = w.i1 - 1,
      c = w.compare,
      d = w.data,
      n = d.length - 1;

  if (r0 > 0 && !c(d[r0], d[r0-1])) w.i0 = bisect.left(d, d[r0]);
  if (r1 < n && !c(d[r1], d[r1+1])) w.i1 = bisect.right(d, d[r1]);
}



var tx = /*#__PURE__*/Object.freeze({
  __proto__: null,
  aggregate: Aggregate,
  bin: Bin,
  collect: Collect,
  compare: Compare,
  countpattern: CountPattern,
  cross: Cross,
  density: Density,
  dotbin: DotBin,
  expression: Expression,
  extent: Extent,
  facet: Facet,
  field: Field,
  filter: Filter,
  flatten: Flatten,
  fold: Fold,
  formula: Formula,
  generate: Generate,
  impute: Impute,
  joinaggregate: JoinAggregate,
  kde: KDE,
  key: Key,
  load: Load,
  lookup: Lookup,
  multiextent: MultiExtent,
  multivalues: MultiValues,
  params: Params,
  pivot: Pivot,
  prefacet: PreFacet,
  project: Project,
  proxy: Proxy,
  quantile: Quantile,
  relay: Relay,
  sample: Sample,
  sequence: Sequence,
  sieve: Sieve,
  subflow: Subflow,
  timeunit: TimeUnit,
  tupleindex: TupleIndex,
  values: Values,
  window: Window
});

const Top = 'top';
const Left = 'left';
const Right = 'right';
const Bottom = 'bottom';

const TopLeft = 'top-left';
const TopRight = 'top-right';
const BottomLeft = 'bottom-left';
const BottomRight = 'bottom-right';

const Start = 'start';
const Middle = 'middle';
const End = 'end';

const X = 'x';
const Y = 'y';

const Group = 'group';

const AxisRole = 'axis';
const TitleRole = 'title';
const FrameRole = 'frame';
const ScopeRole = 'scope';
const LegendRole = 'legend';

const RowHeader = 'row-header';
const RowFooter = 'row-footer';
const RowTitle  = 'row-title';
const ColHeader = 'column-header';
const ColFooter = 'column-footer';
const ColTitle  = 'column-title';

const Padding = 'padding';

const Symbols = 'symbol';

const Fit  = 'fit';
const FitX = 'fit-x';
const FitY = 'fit-y';
const Pad  = 'pad';
const None$1 = 'none';

const All = 'all';
const Each = 'each';
const Flush = 'flush';

const Column = 'column';
const Row = 'row';

function Bounds(b) {
  this.clear();
  if (b) this.union(b);
}

var prototype$G = Bounds.prototype;

prototype$G.clone = function() {
  return new Bounds(this);
};

prototype$G.clear = function() {
  this.x1 = +Number.MAX_VALUE;
  this.y1 = +Number.MAX_VALUE;
  this.x2 = -Number.MAX_VALUE;
  this.y2 = -Number.MAX_VALUE;
  return this;
};

prototype$G.empty = function() {
  return (
    this.x1 === +Number.MAX_VALUE &&
    this.y1 === +Number.MAX_VALUE &&
    this.x2 === -Number.MAX_VALUE &&
    this.y2 === -Number.MAX_VALUE
  );
};

prototype$G.equals = function(b) {
  return (
    this.x1 === b.x1 &&
    this.y1 === b.y1 &&
    this.x2 === b.x2 &&
    this.y2 === b.y2
  );
};

prototype$G.set = function(x1, y1, x2, y2) {
  if (x2 < x1) {
    this.x2 = x1;
    this.x1 = x2;
  } else {
    this.x1 = x1;
    this.x2 = x2;
  }
  if (y2 < y1) {
    this.y2 = y1;
    this.y1 = y2;
  } else {
    this.y1 = y1;
    this.y2 = y2;
  }
  return this;
};

prototype$G.add = function(x, y) {
  if (x < this.x1) this.x1 = x;
  if (y < this.y1) this.y1 = y;
  if (x > this.x2) this.x2 = x;
  if (y > this.y2) this.y2 = y;
  return this;
};

prototype$G.expand = function(d) {
  this.x1 -= d;
  this.y1 -= d;
  this.x2 += d;
  this.y2 += d;
  return this;
};

prototype$G.round = function() {
  this.x1 = Math.floor(this.x1);
  this.y1 = Math.floor(this.y1);
  this.x2 = Math.ceil(this.x2);
  this.y2 = Math.ceil(this.y2);
  return this;
};

prototype$G.translate = function(dx, dy) {
  this.x1 += dx;
  this.x2 += dx;
  this.y1 += dy;
  this.y2 += dy;
  return this;
};

prototype$G.rotate = function(angle, x, y) {
  const p = this.rotatedPoints(angle, x, y);
  return this.clear()
    .add(p[0], p[1])
    .add(p[2], p[3])
    .add(p[4], p[5])
    .add(p[6], p[7]);
};

prototype$G.rotatedPoints = function(angle, x, y) {
  var {x1, y1, x2, y2} = this,
      cos = Math.cos(angle),
      sin = Math.sin(angle),
      cx = x - x*cos + y*sin,
      cy = y - x*sin - y*cos;

  return [
    cos*x1 - sin*y1 + cx, sin*x1 + cos*y1 + cy,
    cos*x1 - sin*y2 + cx, sin*x1 + cos*y2 + cy,
    cos*x2 - sin*y1 + cx, sin*x2 + cos*y1 + cy,
    cos*x2 - sin*y2 + cx, sin*x2 + cos*y2 + cy
  ];
};

prototype$G.union = function(b) {
  if (b.x1 < this.x1) this.x1 = b.x1;
  if (b.y1 < this.y1) this.y1 = b.y1;
  if (b.x2 > this.x2) this.x2 = b.x2;
  if (b.y2 > this.y2) this.y2 = b.y2;
  return this;
};

prototype$G.intersect = function(b) {
  if (b.x1 > this.x1) this.x1 = b.x1;
  if (b.y1 > this.y1) this.y1 = b.y1;
  if (b.x2 < this.x2) this.x2 = b.x2;
  if (b.y2 < this.y2) this.y2 = b.y2;
  return this;
};

prototype$G.encloses = function(b) {
  return b && (
    this.x1 <= b.x1 &&
    this.x2 >= b.x2 &&
    this.y1 <= b.y1 &&
    this.y2 >= b.y2
  );
};

prototype$G.alignsWith = function(b) {
  return b && (
    this.x1 == b.x1 ||
    this.x2 == b.x2 ||
    this.y1 == b.y1 ||
    this.y2 == b.y2
  );
};

prototype$G.intersects = function(b) {
  return b && !(
    this.x2 < b.x1 ||
    this.x1 > b.x2 ||
    this.y2 < b.y1 ||
    this.y1 > b.y2
  );
};

prototype$G.contains = function(x, y) {
  return !(
    x < this.x1 ||
    x > this.x2 ||
    y < this.y1 ||
    y > this.y2
  );
};

prototype$G.width = function() {
  return this.x2 - this.x1;
};

prototype$G.height = function() {
  return this.y2 - this.y1;
};

var gradient_id = 0;

const patternPrefix = 'p_';

function isGradient(value) {
  return value && value.gradient;
}

function gradientRef(g, defs, base) {
  let id = g.id,
      type = g.gradient,
      prefix = type === 'radial' ? patternPrefix : '';

  // check id, assign default values as needed
  if (!id) {
    id = g.id = 'gradient_' + (gradient_id++);
    if (type === 'radial') {
      g.x1 = get$1(g.x1, 0.5);
      g.y1 = get$1(g.y1, 0.5);
      g.r1 = get$1(g.r1, 0);
      g.x2 = get$1(g.x2, 0.5);
      g.y2 = get$1(g.y2, 0.5);
      g.r2 = get$1(g.r2, 0.5);
      prefix = patternPrefix;
    } else {
      g.x1 = get$1(g.x1, 0);
      g.y1 = get$1(g.y1, 0);
      g.x2 = get$1(g.x2, 1);
      g.y2 = get$1(g.y2, 0);
    }
  }

  // register definition
  defs[id] = g;

  // return url reference
  return 'url(' + (base || '') + '#' + prefix + id + ')';
}

function get$1(val, def) {
  return val != null ? val : def;
}

function Gradient(p0, p1) {
  var stops = [], gradient;
  return gradient = {
    gradient: 'linear',
    x1: p0 ? p0[0] : 0,
    y1: p0 ? p0[1] : 0,
    x2: p1 ? p1[0] : 1,
    y2: p1 ? p1[1] : 0,
    stops: stops,
    stop: function(offset, color) {
      stops.push({offset: offset, color: color});
      return gradient;
    }
  };
}

function Item(mark) {
  this.mark = mark;
  this.bounds = (this.bounds || new Bounds());
}

function GroupItem(mark) {
  Item.call(this, mark);
  this.items = (this.items || []);
}

inherits(GroupItem, Item);

function domCanvas(w, h) {
  if (typeof document !== 'undefined' && document.createElement) {
    var c = document.createElement('canvas');
    if (c && c.getContext) {
      c.width = w;
      c.height = h;
      return c;
    }
  }
  return null;
}

function domImage() {
  return typeof Image !== 'undefined' ? Image : null;
}

function ResourceLoader(customLoader) {
  this._pending = 0;
  this._loader = customLoader || loader();
}

var prototype$H = ResourceLoader.prototype;

prototype$H.pending = function() {
  return this._pending;
};

function increment(loader) {
  loader._pending += 1;
}

function decrement(loader) {
  loader._pending -= 1;
}

prototype$H.sanitizeURL = function(uri) {
  var loader = this;
  increment(loader);

  return loader._loader.sanitize(uri, {context:'href'})
    .then(function(opt) {
      decrement(loader);
      return opt;
    })
    .catch(function() {
      decrement(loader);
      return null;
    });
};

prototype$H.loadImage = function(uri) {
  var loader = this,
      Image = domImage();
  increment(loader);

  return loader._loader
    .sanitize(uri, {context: 'image'})
    .then(function(opt) {
      var url = opt.href;
      if (!url || !Image) throw {url: url};

      var img = new Image();

      img.onload = function() {
        decrement(loader);
      };

      img.onerror = function() {
        decrement(loader);
      };

      img.src = url;
      return img;
    })
    .catch(function(e) {
      decrement(loader);
      return {complete: false, width: 0, height: 0, src: e && e.url || ''};
    });
};

prototype$H.ready = function() {
  var loader = this;
  return new Promise(function(accept) {
    function poll(value) {
      if (!loader.pending()) accept(value);
      else setTimeout(function() { poll(true); }, 10);
    }
    poll(false);
  });
};

var lookup = {
  'basis': {
    curve: curveBasis
  },
  'basis-closed': {
    curve: curveBasisClosed
  },
  'basis-open': {
    curve: curveBasisOpen
  },
  'bundle': {
    curve: curveBundle,
    tension: 'beta',
    value: 0.85
  },
  'cardinal': {
    curve: curveCardinal,
    tension: 'tension',
    value: 0
  },
  'cardinal-open': {
    curve: curveCardinalOpen,
    tension: 'tension',
    value: 0
  },
  'cardinal-closed': {
    curve: curveCardinalClosed,
    tension: 'tension',
    value: 0
  },
  'catmull-rom': {
    curve: curveCatmullRom,
    tension: 'alpha',
    value: 0.5
  },
  'catmull-rom-closed': {
    curve: curveCatmullRomClosed,
    tension: 'alpha',
    value: 0.5
  },
  'catmull-rom-open': {
    curve: curveCatmullRomOpen,
    tension: 'alpha',
    value: 0.5
  },
  'linear': {
    curve: curveLinear
  },
  'linear-closed': {
    curve: curveLinearClosed
  },
  'monotone': {
    horizontal: curveMonotoneY,
    vertical:   curveMonotoneX
  },
  'natural': {
    curve: curveNatural
  },
  'step': {
    curve: curveStep
  },
  'step-after': {
    curve: curveStepAfter
  },
  'step-before': {
    curve: curveStepBefore
  }
};

function curves(type, orientation, tension) {
  var entry = hasOwnProperty(lookup, type) && lookup[type],
      curve = null;

  if (entry) {
    curve = entry.curve || entry[orientation || 'vertical'];
    if (entry.tension && tension != null) {
      curve = curve[entry.tension](tension);
    }
  }

  return curve;
}

// Path parsing and rendering code adapted from fabric.js -- Thanks!
var cmdlen = { m:2, l:2, h:1, v:1, c:6, s:4, q:4, t:2, a:7 },
    regexp = [/([MLHVCSQTAZmlhvcsqtaz])/g, /###/, /(\d)([-+])/g, /\s|,|###/];

function pathParse(pathstr) {
  var result = [],
      path,
      curr,
      chunks,
      parsed, param,
      cmd, len, i, j, n, m;

  // First, break path into command sequence
  path = pathstr
    .slice()
    .replace(regexp[0], '###$1')
    .split(regexp[1])
    .slice(1);

  // Next, parse each command in turn
  for (i=0, n=path.length; i<n; ++i) {
    curr = path[i];
    chunks = curr
      .slice(1)
      .trim()
      .replace(regexp[2],'$1###$2')
      .split(regexp[3]);
    cmd = curr.charAt(0);

    parsed = [cmd];
    for (j=0, m=chunks.length; j<m; ++j) {
      if ((param = +chunks[j]) === param) { // not NaN
        parsed.push(param);
      }
    }

    len = cmdlen[cmd.toLowerCase()];
    if (parsed.length-1 > len) {
      for (j=1, m=parsed.length; j<m; j+=len) {
        result.push([cmd].concat(parsed.slice(j, j+len)));
      }
    }
    else {
      result.push(parsed);
    }
  }

  return result;
}

const DegToRad = Math.PI / 180;
const Epsilon = 1e-14;
const HalfPi = Math.PI / 2;
const Tau = Math.PI * 2;
const HalfSqrt3 = Math.sqrt(3) / 2;

var segmentCache = {};
var bezierCache = {};

var join = [].join;

// Copied from Inkscape svgtopdf, thanks!
function segments(x, y, rx, ry, large, sweep, rotateX, ox, oy) {
  var key = join.call(arguments);
  if (segmentCache[key]) {
    return segmentCache[key];
  }

  var th = rotateX * DegToRad;
  var sin_th = Math.sin(th);
  var cos_th = Math.cos(th);
  rx = Math.abs(rx);
  ry = Math.abs(ry);
  var px = cos_th * (ox - x) * 0.5 + sin_th * (oy - y) * 0.5;
  var py = cos_th * (oy - y) * 0.5 - sin_th * (ox - x) * 0.5;
  var pl = (px*px) / (rx*rx) + (py*py) / (ry*ry);
  if (pl > 1) {
    pl = Math.sqrt(pl);
    rx *= pl;
    ry *= pl;
  }

  var a00 = cos_th / rx;
  var a01 = sin_th / rx;
  var a10 = (-sin_th) / ry;
  var a11 = (cos_th) / ry;
  var x0 = a00 * ox + a01 * oy;
  var y0 = a10 * ox + a11 * oy;
  var x1 = a00 * x + a01 * y;
  var y1 = a10 * x + a11 * y;

  var d = (x1-x0) * (x1-x0) + (y1-y0) * (y1-y0);
  var sfactor_sq = 1 / d - 0.25;
  if (sfactor_sq < 0) sfactor_sq = 0;
  var sfactor = Math.sqrt(sfactor_sq);
  if (sweep == large) sfactor = -sfactor;
  var xc = 0.5 * (x0 + x1) - sfactor * (y1-y0);
  var yc = 0.5 * (y0 + y1) + sfactor * (x1-x0);

  var th0 = Math.atan2(y0-yc, x0-xc);
  var th1 = Math.atan2(y1-yc, x1-xc);

  var th_arc = th1-th0;
  if (th_arc < 0 && sweep === 1) {
    th_arc += Tau;
  } else if (th_arc > 0 && sweep === 0) {
    th_arc -= Tau;
  }

  var segs = Math.ceil(Math.abs(th_arc / (HalfPi + 0.001)));
  var result = [];
  for (var i=0; i<segs; ++i) {
    var th2 = th0 + i * th_arc / segs;
    var th3 = th0 + (i+1) * th_arc / segs;
    result[i] = [xc, yc, th2, th3, rx, ry, sin_th, cos_th];
  }

  return (segmentCache[key] = result);
}

function bezier(params) {
  var key = join.call(params);
  if (bezierCache[key]) {
    return bezierCache[key];
  }

  var cx = params[0],
      cy = params[1],
      th0 = params[2],
      th1 = params[3],
      rx = params[4],
      ry = params[5],
      sin_th = params[6],
      cos_th = params[7];

  var a00 = cos_th * rx;
  var a01 = -sin_th * ry;
  var a10 = sin_th * rx;
  var a11 = cos_th * ry;

  var cos_th0 = Math.cos(th0);
  var sin_th0 = Math.sin(th0);
  var cos_th1 = Math.cos(th1);
  var sin_th1 = Math.sin(th1);

  var th_half = 0.5 * (th1 - th0);
  var sin_th_h2 = Math.sin(th_half * 0.5);
  var t = (8/3) * sin_th_h2 * sin_th_h2 / Math.sin(th_half);
  var x1 = cx + cos_th0 - t * sin_th0;
  var y1 = cy + sin_th0 + t * cos_th0;
  var x3 = cx + cos_th1;
  var y3 = cy + sin_th1;
  var x2 = x3 + t * sin_th1;
  var y2 = y3 - t * cos_th1;

  return (bezierCache[key] = [
    a00 * x1 + a01 * y1,  a10 * x1 + a11 * y1,
    a00 * x2 + a01 * y2,  a10 * x2 + a11 * y2,
    a00 * x3 + a01 * y3,  a10 * x3 + a11 * y3
  ]);
}

var temp = ['l', 0, 0, 0, 0, 0, 0, 0];

function scale(current, sX, sY) {
  var c = (temp[0] = current[0]);
  if (c === 'a' || c === 'A') {
    temp[1] = sX * current[1];
    temp[2] = sY * current[2];
    temp[3] = current[3];
    temp[4] = current[4];
    temp[5] = current[5];
    temp[6] = sX * current[6];
    temp[7] = sY * current[7];
  } else if (c === 'h' || c === 'H') {
    temp[1] = sX * current[1];
  } else if (c === 'v' || c === 'V') {
    temp[1] = sY * current[1];
  } else {
    for (var i=1, n=current.length; i<n; ++i) {
      temp[i] = (i % 2 == 1 ? sX : sY) * current[i];
    }
  }
  return temp;
}

function pathRender(context, path, l, t, sX, sY) {
  var current, // current instruction
      previous = null,
      x = 0, // current x
      y = 0, // current y
      controlX = 0, // current control point x
      controlY = 0, // current control point y
      tempX,
      tempY,
      tempControlX,
      tempControlY;

  if (l == null) l = 0;
  if (t == null) t = 0;
  if (sX == null) sX = 1;
  if (sY == null) sY = sX;

  if (context.beginPath) context.beginPath();

  for (var i=0, len=path.length; i<len; ++i) {
    current = path[i];
    if (sX !== 1 || sY !== 1) {
      current = scale(current, sX, sY);
    }

    switch (current[0]) { // first letter

      case 'l': // lineto, relative
        x += current[1];
        y += current[2];
        context.lineTo(x + l, y + t);
        break;

      case 'L': // lineto, absolute
        x = current[1];
        y = current[2];
        context.lineTo(x + l, y + t);
        break;

      case 'h': // horizontal lineto, relative
        x += current[1];
        context.lineTo(x + l, y + t);
        break;

      case 'H': // horizontal lineto, absolute
        x = current[1];
        context.lineTo(x + l, y + t);
        break;

      case 'v': // vertical lineto, relative
        y += current[1];
        context.lineTo(x + l, y + t);
        break;

      case 'V': // verical lineto, absolute
        y = current[1];
        context.lineTo(x + l, y + t);
        break;

      case 'm': // moveTo, relative
        x += current[1];
        y += current[2];
        context.moveTo(x + l, y + t);
        break;

      case 'M': // moveTo, absolute
        x = current[1];
        y = current[2];
        context.moveTo(x + l, y + t);
        break;

      case 'c': // bezierCurveTo, relative
        tempX = x + current[5];
        tempY = y + current[6];
        controlX = x + current[3];
        controlY = y + current[4];
        context.bezierCurveTo(
          x + current[1] + l, // x1
          y + current[2] + t, // y1
          controlX + l, // x2
          controlY + t, // y2
          tempX + l,
          tempY + t
        );
        x = tempX;
        y = tempY;
        break;

      case 'C': // bezierCurveTo, absolute
        x = current[5];
        y = current[6];
        controlX = current[3];
        controlY = current[4];
        context.bezierCurveTo(
          current[1] + l,
          current[2] + t,
          controlX + l,
          controlY + t,
          x + l,
          y + t
        );
        break;

      case 's': // shorthand cubic bezierCurveTo, relative
        // transform to absolute x,y
        tempX = x + current[3];
        tempY = y + current[4];
        // calculate reflection of previous control points
        controlX = 2 * x - controlX;
        controlY = 2 * y - controlY;
        context.bezierCurveTo(
          controlX + l,
          controlY + t,
          x + current[1] + l,
          y + current[2] + t,
          tempX + l,
          tempY + t
        );

        // set control point to 2nd one of this command
        // the first control point is assumed to be the reflection of
        // the second control point on the previous command relative
        // to the current point.
        controlX = x + current[1];
        controlY = y + current[2];

        x = tempX;
        y = tempY;
        break;

      case 'S': // shorthand cubic bezierCurveTo, absolute
        tempX = current[3];
        tempY = current[4];
        // calculate reflection of previous control points
        controlX = 2*x - controlX;
        controlY = 2*y - controlY;
        context.bezierCurveTo(
          controlX + l,
          controlY + t,
          current[1] + l,
          current[2] + t,
          tempX + l,
          tempY + t
        );
        x = tempX;
        y = tempY;
        // set control point to 2nd one of this command
        // the first control point is assumed to be the reflection of
        // the second control point on the previous command relative
        // to the current point.
        controlX = current[1];
        controlY = current[2];

        break;

      case 'q': // quadraticCurveTo, relative
        // transform to absolute x,y
        tempX = x + current[3];
        tempY = y + current[4];

        controlX = x + current[1];
        controlY = y + current[2];

        context.quadraticCurveTo(
          controlX + l,
          controlY + t,
          tempX + l,
          tempY + t
        );
        x = tempX;
        y = tempY;
        break;

      case 'Q': // quadraticCurveTo, absolute
        tempX = current[3];
        tempY = current[4];

        context.quadraticCurveTo(
          current[1] + l,
          current[2] + t,
          tempX + l,
          tempY + t
        );
        x = tempX;
        y = tempY;
        controlX = current[1];
        controlY = current[2];
        break;

      case 't': // shorthand quadraticCurveTo, relative

        // transform to absolute x,y
        tempX = x + current[1];
        tempY = y + current[2];

        if (previous[0].match(/[QqTt]/) === null) {
          // If there is no previous command or if the previous command was not a Q, q, T or t,
          // assume the control point is coincident with the current point
          controlX = x;
          controlY = y;
        }
        else if (previous[0] === 't') {
          // calculate reflection of previous control points for t
          controlX = 2 * x - tempControlX;
          controlY = 2 * y - tempControlY;
        }
        else if (previous[0] === 'q') {
          // calculate reflection of previous control points for q
          controlX = 2 * x - controlX;
          controlY = 2 * y - controlY;
        }

        tempControlX = controlX;
        tempControlY = controlY;

        context.quadraticCurveTo(
          controlX + l,
          controlY + t,
          tempX + l,
          tempY + t
        );
        x = tempX;
        y = tempY;
        controlX = x + current[1];
        controlY = y + current[2];
        break;

      case 'T':
        tempX = current[1];
        tempY = current[2];

        // calculate reflection of previous control points
        controlX = 2 * x - controlX;
        controlY = 2 * y - controlY;
        context.quadraticCurveTo(
          controlX + l,
          controlY + t,
          tempX + l,
          tempY + t
        );
        x = tempX;
        y = tempY;
        break;

      case 'a':
        drawArc(context, x + l, y + t, [
          current[1],
          current[2],
          current[3],
          current[4],
          current[5],
          current[6] + x + l,
          current[7] + y + t
        ]);
        x += current[6];
        y += current[7];
        break;

      case 'A':
        drawArc(context, x + l, y + t, [
          current[1],
          current[2],
          current[3],
          current[4],
          current[5],
          current[6] + l,
          current[7] + t
        ]);
        x = current[6];
        y = current[7];
        break;

      case 'z':
      case 'Z':
        context.closePath();
        break;
    }
    previous = current;
  }
}

function drawArc(context, x, y, coords) {
  var seg = segments(
    coords[5], // end x
    coords[6], // end y
    coords[0], // radius x
    coords[1], // radius y
    coords[3], // large flag
    coords[4], // sweep flag
    coords[2], // rotation
    x, y
  );
  for (var i=0; i<seg.length; ++i) {
    var bez = bezier(seg[i]);
    context.bezierCurveTo(bez[0], bez[1], bez[2], bez[3], bez[4], bez[5]);
  }
}

var Tan30 = 0.5773502691896257;

var builtins = {
  'circle': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2;
      context.moveTo(r, 0);
      context.arc(0, 0, r, 0, Tau);
    }
  },
  'cross': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2,
          s = r / 2.5;
      context.moveTo(-r, -s);
      context.lineTo(-r, s);
      context.lineTo(-s, s);
      context.lineTo(-s, r);
      context.lineTo(s, r);
      context.lineTo(s, s);
      context.lineTo(r, s);
      context.lineTo(r, -s);
      context.lineTo(s, -s);
      context.lineTo(s, -r);
      context.lineTo(-s, -r);
      context.lineTo(-s, -s);
      context.closePath();
    }
  },
  'diamond': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2;
      context.moveTo(-r, 0);
      context.lineTo(0, -r);
      context.lineTo(r, 0);
      context.lineTo(0, r);
      context.closePath();
    }
  },
  'square': {
    draw: function(context, size) {
      var w = Math.sqrt(size),
          x = -w / 2;
      context.rect(x, x, w, w);
    }
  },
  'arrow': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2,
          s = r / 7,
          t = r / 2.5,
          v = r / 8;
      context.moveTo(-s, r);
      context.lineTo(s, r);
      context.lineTo(s, -v);
      context.lineTo(t, -v);
      context.lineTo(0, -r);
      context.lineTo(-t, -v);
      context.lineTo(-s, -v);
      context.closePath();
    }
  },
  'wedge': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2,
          h = HalfSqrt3 * r,
          o = (h - r * Tan30),
          b = r / 4;
      context.moveTo(0, -h - o);
      context.lineTo(-b, h - o);
      context.lineTo(b, h - o);
      context.closePath();
    }
  },
  'triangle': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2,
          h = HalfSqrt3 * r,
          o = (h - r * Tan30);
      context.moveTo(0, -h - o);
      context.lineTo(-r, h - o);
      context.lineTo(r, h - o);
      context.closePath();
    }
  },
  'triangle-up': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2,
          h = HalfSqrt3 * r;
      context.moveTo(0, -h);
      context.lineTo(-r, h);
      context.lineTo(r, h);
      context.closePath();
    }
  },
  'triangle-down': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2,
          h = HalfSqrt3 * r;
      context.moveTo(0, h);
      context.lineTo(-r, -h);
      context.lineTo(r, -h);
      context.closePath();
    }
  },
  'triangle-right': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2,
          h = HalfSqrt3 * r;
      context.moveTo(h, 0);
      context.lineTo(-h, -r);
      context.lineTo(-h, r);
      context.closePath();
    }
  },
  'triangle-left': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2,
          h = HalfSqrt3 * r;
      context.moveTo(-h, 0);
      context.lineTo(h, -r);
      context.lineTo(h, r);
      context.closePath();
    }
  },
  'stroke': {
    draw: function(context, size) {
      var r = Math.sqrt(size) / 2;
      context.moveTo(-r, 0);
      context.lineTo(r, 0);
    }
  }
};

function symbols(_) {
  return hasOwnProperty(builtins, _) ? builtins[_] : customSymbol(_);
}

var custom = {};

function customSymbol(path) {
  if (!hasOwnProperty(custom, path)) {
    var parsed = pathParse(path);
    custom[path] = {
      draw: function(context, size) {
        pathRender(context, parsed, 0, 0, Math.sqrt(size) / 2);
      }
    };
  }
  return custom[path];
}

// See http://spencermortensen.com/articles/bezier-circle/
const C = 0.448084975506; // C = 1 - c

function rectangleX(d) {
  return d.x;
}

function rectangleY(d) {
  return d.y;
}

function rectangleWidth(d) {
  return d.width;
}

function rectangleHeight(d) {
  return d.height;
}

function number$1(_) {
  return typeof _ === 'function' ? _ : () => +_;
}

function clamp(value, min, max) {
  return Math.max(min, Math.min(value, max));
}

function vg_rect() {
  var x = rectangleX,
      y = rectangleY,
      width = rectangleWidth,
      height = rectangleHeight,
      crTL = number$1(0),
      crTR = crTL,
      crBL = crTL,
      crBR = crTL,
      context = null;

  function rectangle(_, x0, y0) {
    var buffer,
        x1 = x0 != null ? x0 : +x.call(this, _),
        y1 = y0 != null ? y0 : +y.call(this, _),
        w  = +width.call(this, _),
        h  = +height.call(this, _),
        s  = Math.min(w, h) / 2,
        tl = clamp(+crTL.call(this, _), 0, s),
        tr = clamp(+crTR.call(this, _), 0, s),
        bl = clamp(+crBL.call(this, _), 0, s),
        br = clamp(+crBR.call(this, _), 0, s);

    if (!context) context = buffer = path$3();

    if (tl <= 0 && tr <= 0 && bl <= 0 && br <= 0) {
      context.rect(x1, y1, w, h);
    } else {
      var x2 = x1 + w,
          y2 = y1 + h;
      context.moveTo(x1 + tl, y1);
      context.lineTo(x2 - tr, y1);
      context.bezierCurveTo(x2 - C * tr, y1, x2, y1 + C * tr, x2, y1 + tr);
      context.lineTo(x2, y2 - br);
      context.bezierCurveTo(x2, y2 - C * br, x2 - C * br, y2, x2 - br, y2);
      context.lineTo(x1 + bl, y2);
      context.bezierCurveTo(x1 + C * bl, y2, x1, y2 - C * bl, x1, y2 - bl);
      context.lineTo(x1, y1 + tl);
      context.bezierCurveTo(x1, y1 + C * tl, x1 + C * tl, y1, x1 + tl, y1);
      context.closePath();
    }

    if (buffer) {
      context = null;
      return buffer + '' || null;
    }
  }

  rectangle.x = function(_) {
    if (arguments.length) {
      x = number$1(_);
      return rectangle;
    } else {
      return x;
    }
  };

  rectangle.y = function(_) {
    if (arguments.length) {
      y = number$1(_);
      return rectangle;
    } else {
      return y;
    }
  };

  rectangle.width = function(_) {
    if (arguments.length) {
      width = number$1(_);
      return rectangle;
    } else {
      return width;
    }
  };

  rectangle.height = function(_) {
    if (arguments.length) {
      height = number$1(_);
      return rectangle;
    } else {
      return height;
    }
  };

  rectangle.cornerRadius = function(tl, tr, br, bl) {
    if (arguments.length) {
      crTL = number$1(tl);
      crTR = tr != null ? number$1(tr) : crTL;
      crBR = br != null ? number$1(br) : crTL;
      crBL = bl != null ? number$1(bl) : crTR;
      return rectangle;
    } else {
      return crTL;
    }
  };

  rectangle.context = function(_) {
    if (arguments.length) {
      context = _ == null ? null : _;
      return rectangle;
    } else {
      return context;
    }
  };

  return rectangle;
}

function vg_trail() {
  var x,
      y,
      size,
      defined,
      context = null,
      ready, x1, y1, r1;

  function point(x2, y2, w2) {
    var r2 = w2 / 2;

    if (ready) {
      var ux = y1 - y2,
          uy = x2 - x1;

      if (ux || uy) {
        // get normal vector
        var ud = Math.sqrt(ux * ux + uy * uy),
            rx = (ux /= ud) * r1,
            ry = (uy /= ud) * r1,
            t = Math.atan2(uy, ux);

        // draw segment
        context.moveTo(x1 - rx, y1 - ry);
        context.lineTo(x2 - ux * r2, y2 - uy * r2);
        context.arc(x2, y2, r2, t - Math.PI, t);
        context.lineTo(x1 + rx, y1 + ry);
        context.arc(x1, y1, r1, t, t + Math.PI);
      } else {
        context.arc(x2, y2, r2, 0, Tau);
      }
      context.closePath();
    } else {
      ready = 1;
    }
    x1 = x2;
    y1 = y2;
    r1 = r2;
  }

  function trail(data) {
    var i,
        n = data.length,
        d,
        defined0 = false,
        buffer;

    if (context == null) context = buffer = path$3();

    for (i = 0; i <= n; ++i) {
      if (!(i < n && defined(d = data[i], i, data)) === defined0) {
        if (defined0 = !defined0) ready = 0;
      }
      if (defined0) point(+x(d, i, data), +y(d, i, data), +size(d, i, data));
    }

    if (buffer) {
      context = null;
      return buffer + '' || null;
    }
  }

  trail.x = function(_) {
    if (arguments.length) {
      x = _;
      return trail;
    } else {
      return x;
    }
  };

  trail.y = function(_) {
    if (arguments.length) {
      y = _;
      return trail;
    } else {
      return y;
    }
  };

  trail.size = function(_) {
    if (arguments.length) {
      size = _;
      return trail;
    } else {
      return size;
    }
  };

  trail.defined = function(_) {
    if (arguments.length) {
      defined = _;
      return trail;
    } else {
      return defined;
    }
  };

  trail.context = function(_) {
    if (arguments.length) {
      if (_ == null) {
        context = null;
      } else {
        context = _;
      }
      return trail;
    } else {
      return context;
    }
  };

  return trail;
}

function value(a, b) {
  return a != null ? a : b;
}

const x =  item => item.x || 0,
      y =  item => item.y || 0,
      w =  item => item.width || 0,
      h =  item => item.height || 0,
      xw = item => (item.x || 0) + (item.width || 0),
      yh = item => (item.y || 0) + (item.height || 0),
      sa = item => item.startAngle || 0,
      ea = item => item.endAngle || 0,
      pa = item => item.padAngle || 0,
      ir = item => item.innerRadius || 0,
      or = item => item.outerRadius || 0,
      cr = item => item.cornerRadius || 0,
      tl = item => value(item.cornerRadiusTopLeft, item.cornerRadius) || 0,
      tr = item => value(item.cornerRadiusTopRight, item.cornerRadius) || 0,
      br = item => value(item.cornerRadiusBottomRight, item.cornerRadius) || 0,
      bl = item => value(item.cornerRadiusBottomLeft, item.cornerRadius) || 0,
      sz = item => value(item.size, 64),
      ts = item => item.size || 1,
      def = item => !(item.defined === false),
      type = item => symbols(item.shape || 'circle');

const arcShape    = arc$3().startAngle(sa).endAngle(ea).padAngle(pa)
                      .innerRadius(ir).outerRadius(or).cornerRadius(cr),
      areavShape  = area$3().x(x).y1(y).y0(yh).defined(def),
      areahShape  = area$3().y(y).x1(x).x0(xw).defined(def),
      lineShape   = line$3().x(x).y(y).defined(def),
      rectShape   = vg_rect().x(x).y(y).width(w).height(h)
                      .cornerRadius(tl, tr, br, bl),
      symbolShape = symbol$2().type(type).size(sz),
      trailShape  = vg_trail().x(x).y(y).defined(def).size(ts);

function hasCornerRadius(item) {
  return item.cornerRadius
    || item.cornerRadiusTopLeft
    || item.cornerRadiusTopRight
    || item.cornerRadiusBottomRight
    || item.cornerRadiusBottomLeft;
}

function arc(context, item) {
  return arcShape.context(context)(item);
}

function area(context, items) {
  var item = items[0],
      interp = item.interpolate || 'linear';
  return (item.orient === 'horizontal' ? areahShape : areavShape)
    .curve(curves(interp, item.orient, item.tension))
    .context(context)(items);
}

function line(context, items) {
  var item = items[0],
      interp = item.interpolate || 'linear';
  return lineShape.curve(curves(interp, item.orient, item.tension))
    .context(context)(items);
}

function rectangle(context, item, x, y) {
  return rectShape.context(context)(item, x, y);
}

function shape(context, item) {
  return (item.mark.shape || item.shape)
    .context(context)(item);
}

function symbol(context, item) {
  return symbolShape.context(context)(item);
}

function trail(context, items) {
  return trailShape.context(context)(items);
}

function boundStroke(bounds, item, miter) {
  if (item.stroke && item.opacity !== 0 && item.strokeOpacity !== 0) {
    const sw = item.strokeWidth != null ? +item.strokeWidth : 1;
    bounds.expand(sw + (miter ? miterAdjustment(item, sw) : 0));
  }
  return bounds;
}

function miterAdjustment(item, strokeWidth) {
  // TODO: more sophisticated adjustment? Or miter support in boundContext?
  return item.strokeJoin && item.strokeJoin !== 'miter' ? 0 : strokeWidth;
}

var bounds, lx, ly,
    circleThreshold = Tau - 1e-8;

function context(_) {
  bounds = _;
  return context;
}

function noop() {}

function add$1(x, y) { bounds.add(x, y); }

function addL(x, y) { add$1(lx = x, ly = y); }

function addX(x) { add$1(x, bounds.y1); }

function addY(y) { add$1(bounds.x1, y); }

context.beginPath = noop;

context.closePath = noop;

context.moveTo = addL;

context.lineTo = addL;

context.rect = function(x, y, w, h) {
  add$1(x + w, y + h);
  addL(x, y);
};

context.quadraticCurveTo = function(x1, y1, x2, y2) {
  quadExtrema(lx, x1, x2, addX);
  quadExtrema(ly, y1, y2, addY);
  addL(x2, y2);
};

function quadExtrema(x0, x1, x2, cb) {
  const t = (x0 - x1) / (x0 + x2 - 2 * x1);
  if (0 < t && t < 1) cb(x0 + (x1 - x0) * t);
}

context.bezierCurveTo = function(x1, y1, x2, y2, x3, y3) {
  cubicExtrema(lx, x1, x2, x3, addX);
  cubicExtrema(ly, y1, y2, y3, addY);
  addL(x3, y3);
};

function cubicExtrema(x0, x1, x2, x3, cb) {
  const a = x3 - x0 + 3 * x1 - 3 * x2,
        b = x0 + x2 - 2 * x1,
        c = x0 - x1;

  let t0 = 0, t1 = 0, r;

  // solve for parameter t
  if (Math.abs(a) > Epsilon) {
    // quadratic equation
    r = b * b + c * a;
    if (r >= 0) {
      r = Math.sqrt(r);
      t0 = (-b + r) / a;
      t1 = (-b - r) / a;
    }
  } else {
    // linear equation
    t0 = 0.5 * c / b;
  }

  // calculate position
  if (0 < t0 && t0 < 1) cb(cubic(t0, x0, x1, x2, x3));
  if (0 < t1 && t1 < 1) cb(cubic(t1, x0, x1, x2, x3));
}

function cubic(t, x0, x1, x2, x3) {
  const s = 1 - t, s2 = s * s, t2 = t * t;
  return (s2 * s * x0) + (3 * s2 * t * x1) + (3 * s * t2 * x2) + (t2 * t * x3);
}

context.arc = function(cx, cy, r, sa, ea, ccw) {
  // store last point on path
  lx = r * Math.cos(ea) + cx;
  ly = r * Math.sin(ea) + cy;

  if (Math.abs(ea - sa) > circleThreshold) {
    // treat as full circle
    add$1(cx - r, cy - r);
    add$1(cx + r, cy + r);
  } else {
    const update = a => add$1(r * Math.cos(a) + cx, r * Math.sin(a) + cy);
    let s, i;

    // sample end points
    update(sa);
    update(ea);

    // sample interior points aligned with 90 degrees
    if (ea !== sa) {
      sa = sa % Tau; if (sa < 0) sa += Tau;
      ea = ea % Tau; if (ea < 0) ea += Tau;

      if (ea < sa) {
        ccw = !ccw; // flip direction
        s = sa; sa = ea; ea = s; // swap end-points
      }

      if (ccw) {
        ea -= Tau;
        s = sa - (sa % HalfPi);
        for (i=0; i<4 && s>ea; ++i, s-=HalfPi) update(s);
      } else {
        s = sa - (sa % HalfPi) + HalfPi;
        for (i=0; i<4 && s<ea; ++i, s=s+HalfPi) update(s);
      }
    }
  }
};

var context$1 = (context$1 = domCanvas(1,1))
  ? context$1.getContext('2d')
  : null;

const b = new Bounds();

function intersectPath(draw) {
  return function(item, brush) {
    // rely on (inaccurate) bounds intersection if no context
    if (!context$1) return true;

    // add path to offscreen graphics context
    draw(context$1, item);

    // get bounds intersection region
    b.clear().union(item.bounds).intersect(brush).round();
    const {x1, y1, x2, y2} = b;

    // iterate over intersection region
    // perform fine grained inclusion test
    for (let y = y1; y <= y2; ++y) {
      for (let x = x1; x <= x2; ++x) {
        if (context$1.isPointInPath(x, y)) {
          return true;
        }
      }
    }

    // false if no hits in intersection region
    return false;
  }
}

function intersectPoint(item, box) {
  return box.contains(item.x || 0, item.y || 0);
}

function intersectRect(item, box) {
  const x = item.x || 0,
        y = item.y || 0,
        w = item.width || 0,
        h = item.height || 0;
  return box.intersects(b.set(x, y, x + w, y + h));
}

function intersectRule(item, box) {
  const x = item.x || 0,
        y = item.y || 0,
        x2 = item.x2 != null ? item.x2 : x,
        y2 = item.y2 != null ? item.y2 : y;
  return intersectBoxLine(box, x, y, x2, y2);
}

function intersectBoxLine(box, x, y, u, v) {
  const {x1, y1, x2, y2} = box,
        dx = u - x,
        dy = v - y;

  let t0 = 0, t1 = 1, p, q, r, e;

  for (e=0; e<4; ++e) {
    if (e === 0) { p = -dx; q = -(x1 - x); }
    if (e === 1) { p =  dx; q =  (x2 - x); }
    if (e === 2) { p = -dy; q = -(y1 - y); }
    if (e === 3) { p =  dy; q =  (y2 - y); }

    if (Math.abs(p) < 1e-10 && q < 0) return false;

    r = q / p;

    if (p < 0) {
      if (r > t1) return false;
      else if (r > t0) t0 = r;
    } else if (p > 0) {
      if (r < t0) return false;
      else if (r < t1) t1 = r;
    }
  }

  return true;
}

function gradient(context, gradient, bounds) {
  const w = bounds.width(),
        h = bounds.height(),
        stop = gradient.stops,
        n = stop.length;

  const canvasGradient = gradient.gradient === 'radial'
    ? context.createRadialGradient(
        bounds.x1 + v(gradient.x1, 0.5) * w,
        bounds.y1 + v(gradient.y1, 0.5) * h,
        Math.max(w, h) * v(gradient.r1, 0),
        bounds.x1 + v(gradient.x2, 0.5) * w,
        bounds.y1 + v(gradient.y2, 0.5) * h,
        Math.max(w, h) * v(gradient.r2, 0.5)
      )
    : context.createLinearGradient(
        bounds.x1 + v(gradient.x1, 0) * w,
        bounds.y1 + v(gradient.y1, 0) * h,
        bounds.x1 + v(gradient.x2, 1) * w,
        bounds.y1 + v(gradient.y2, 0) * h
      );

  for (let i=0; i<n; ++i) {
    canvasGradient.addColorStop(stop[i].offset, stop[i].color);
  }

  return canvasGradient;
}

function v(value, dflt) {
  return value == null ? dflt : value;
}

function color(context, item, value) {
  return isGradient(value) ?
    gradient(context, value, item.bounds) :
    value;
}

function fill(context, item, opacity) {
  opacity *= (item.fillOpacity==null ? 1 : item.fillOpacity);
  if (opacity > 0) {
    context.globalAlpha = opacity;
    context.fillStyle = color(context, item, item.fill);
    return true;
  } else {
    return false;
  }
}

var Empty$1 = [];

function stroke(context, item, opacity) {
  var lw = (lw = item.strokeWidth) != null ? lw : 1;

  if (lw <= 0) return false;

  opacity *= (item.strokeOpacity==null ? 1 : item.strokeOpacity);
  if (opacity > 0) {
    context.globalAlpha = opacity;
    context.strokeStyle = color(context, item, item.stroke);

    context.lineWidth = lw;
    context.lineCap = item.strokeCap || 'butt';
    context.lineJoin = item.strokeJoin || 'miter';
    context.miterLimit = item.strokeMiterLimit || 10;

    if (context.setLineDash) {
      context.setLineDash(item.strokeDash || Empty$1);
      context.lineDashOffset = item.strokeDashOffset || 0;
    }
    return true;
  } else {
    return false;
  }
}

function compare$1(a, b) {
  return a.zindex - b.zindex || a.index - b.index;
}

function zorder(scene) {
  if (!scene.zdirty) return scene.zitems;

  var items = scene.items,
      output = [], item, i, n;

  for (i=0, n=items.length; i<n; ++i) {
    item = items[i];
    item.index = i;
    if (item.zindex) output.push(item);
  }

  scene.zdirty = false;
  return scene.zitems = output.sort(compare$1);
}

function visit(scene, visitor) {
  var items = scene.items, i, n;
  if (!items || !items.length) return;

  var zitems = zorder(scene);

  if (zitems && zitems.length) {
    for (i=0, n=items.length; i<n; ++i) {
      if (!items[i].zindex) visitor(items[i]);
    }
    items = zitems;
  }

  for (i=0, n=items.length; i<n; ++i) {
    visitor(items[i]);
  }
}

function pickVisit(scene, visitor) {
  var items = scene.items, hit, i;
  if (!items || !items.length) return null;

  var zitems = zorder(scene);
  if (zitems && zitems.length) items = zitems;

  for (i=items.length; --i >= 0;) {
    if (hit = visitor(items[i])) return hit;
  }

  if (items === zitems) {
    for (items=scene.items, i=items.length; --i >= 0;) {
      if (!items[i].zindex) {
        if (hit = visitor(items[i])) return hit;
      }
    }
  }

  return null;
}

function drawAll(path) {
  return function(context, scene, bounds) {
    visit(scene, function(item) {
      if (!bounds || bounds.intersects(item.bounds)) {
        drawPath(path, context, item, item);
      }
    });
  };
}

function drawOne(path) {
  return function(context, scene, bounds) {
    if (scene.items.length && (!bounds || bounds.intersects(scene.bounds))) {
      drawPath(path, context, scene.items[0], scene.items);
    }
  };
}

function drawPath(path, context, item, items) {
  var opacity = item.opacity == null ? 1 : item.opacity;
  if (opacity === 0) return;

  if (path(context, items)) return;

  if (item.fill && fill(context, item, opacity)) {
    context.fill();
  }

  if (item.stroke && stroke(context, item, opacity)) {
    context.stroke();
  }
}

function pick(test) {
  test = test || truthy;

  return function(context, scene, x, y, gx, gy) {
    x *= context.pixelRatio;
    y *= context.pixelRatio;

    return pickVisit(scene, function(item) {
      var b = item.bounds;
      // first hit test against bounding box
      if ((b && !b.contains(gx, gy)) || !b) return;
      // if in bounding box, perform more careful test
      if (test(context, item, x, y, gx, gy)) return item;
    });
  };
}

function hitPath(path, filled) {
  return function(context, o, x, y) {
    var item = Array.isArray(o) ? o[0] : o,
        fill = (filled == null) ? item.fill : filled,
        stroke = item.stroke && context.isPointInStroke, lw, lc;

    if (stroke) {
      lw = item.strokeWidth;
      lc = item.strokeCap;
      context.lineWidth = lw != null ? lw : 1;
      context.lineCap   = lc != null ? lc : 'butt';
    }

    return path(context, o) ? false :
      (fill && context.isPointInPath(x, y)) ||
      (stroke && context.isPointInStroke(x, y));
  };
}

function pickPath(path) {
  return pick(hitPath(path));
}

function translate(x, y) {
  return 'translate(' + x + ',' + y + ')';
}

function rotate(a) {
  return 'rotate(' + a + ')';
}

function scale$1(scaleX, scaleY){
  return 'scale('+ scaleX + ',' + scaleY+')';
}

function translateItem(item) {
  return translate(item.x || 0, item.y || 0);
}

function transformItem(item) {
  return translate(item.x || 0, item.y || 0)
    + (item.angle ? ' ' + rotate(item.angle) : '')
    + (item.scaleX || item.scaleY ? ' ' + scale$1(item.scaleX || 1, item.scaleY || 1) : '');   
}

function markItemPath(type, shape, isect) {

  function attr(emit, item) {
    emit('transform', transformItem(item));
    emit('d', shape(null, item));
  }

  function bound(bounds, item) {
    var x = item.x || 0,
        y = item.y || 0;

    shape(context(bounds), item);
    boundStroke(bounds, item).translate(x, y);
    if (item.angle) {
      bounds.rotate(item.angle * DegToRad, x, y);
    }

    return bounds;
  }

  function draw(context, item) {
    var x = item.x || 0,
        y = item.y || 0,
        a = item.angle || 0;

    context.translate(x, y);
    if (a) context.rotate(a *= DegToRad);
    context.beginPath();
    shape(context, item);
    if (a) context.rotate(-a);
    context.translate(-x, -y);
  }

  return {
    type:   type,
    tag:    'path',
    nested: false,
    attr:   attr,
    bound:  bound,
    draw:   drawAll(draw),
    pick:   pickPath(draw),
    isect:  isect || intersectPath(draw)
  };

}

var arc$1 = markItemPath('arc', arc);

function pickArea(a, p) {
  var v = a[0].orient === 'horizontal' ? p[1] : p[0],
      z = a[0].orient === 'horizontal' ? 'y' : 'x',
      i = a.length,
      min = +Infinity, hit, d;

  while (--i >= 0) {
    if (a[i].defined === false) continue;
    d = Math.abs(a[i][z] - v);
    if (d < min) {
      min = d;
      hit = a[i];
    }
  }

  return hit;
}

function pickLine(a, p) {
  var t = Math.pow(a[0].strokeWidth || 1, 2),
      i = a.length, dx, dy, dd;

  while (--i >= 0) {
    if (a[i].defined === false) continue;
    dx = a[i].x - p[0];
    dy = a[i].y - p[1];
    dd = dx * dx + dy * dy;
    if (dd < t) return a[i];
  }

  return null;
}

function pickTrail(a, p) {
  var i = a.length, dx, dy, dd;

  while (--i >= 0) {
    if (a[i].defined === false) continue;
    dx = a[i].x - p[0];
    dy = a[i].y - p[1];
    dd = dx * dx + dy * dy;
    dx = a[i].size || 1;
    if (dd < dx*dx) return a[i];
  }

  return null;
}

function markMultiItemPath(type, shape, tip) {

  function attr(emit, item) {
    var items = item.mark.items;
    if (items.length) emit('d', shape(null, items));
  }

  function bound(bounds, mark) {
    var items = mark.items;
    if (items.length === 0) {
      return bounds;
    } else {
      shape(context(bounds), items);
      return boundStroke(bounds, items[0]);
    }
  }

  function draw(context, items) {
    context.beginPath();
    shape(context, items);
  }

  var hit = hitPath(draw);

  function pick(context, scene, x, y, gx, gy) {
    var items = scene.items,
        b = scene.bounds;

    if (!items || !items.length || b && !b.contains(gx, gy)) {
      return null;
    }

    x *= context.pixelRatio;
    y *= context.pixelRatio;
    return hit(context, items, x, y) ? items[0] : null;
  }

  return {
    type:   type,
    tag:    'path',
    nested: true,
    attr:   attr,
    bound:  bound,
    draw:   drawOne(draw),
    pick:   pick,
    isect:  intersectPoint,
    tip:    tip
  };

}

var area$1 = markMultiItemPath('area', area, pickArea);

function clip(context, scene) {
  var clip = scene.clip;

  context.save();

  if (isFunction(clip)) {
    context.beginPath();
    clip(context);
    context.clip();
  } else {
    clipGroup(context, scene.group);
  }
}

function clipGroup(context, group) {
  context.beginPath();
  hasCornerRadius(group)
    ? rectangle(context, group, 0, 0)
    : context.rect(0, 0, group.width || 0, group.height || 0);
  context.clip();
}

var clip_id = 1;

function resetSVGClipId() {
  clip_id = 1;
}

function clip$1(renderer, item, size) {
  var clip = item.clip,
      defs = renderer._defs,
      id = item.clip_id || (item.clip_id = 'clip' + clip_id++),
      c = defs.clipping[id] || (defs.clipping[id] = {id: id});

  if (isFunction(clip)) {
    c.path = clip(null);
  } else if (hasCornerRadius(size)) {
    c.path = rectangle(null, size, 0, 0);
  } else {
    c.width = size.width || 0;
    c.height = size.height || 0;
  }

  return 'url(#' + id + ')';
}

function offset$1(item) {
  var sw = (sw = item.strokeWidth) != null ? sw : 1;
  return item.strokeOffset != null ? item.strokeOffset
    : item.stroke && sw > 0.5 && sw < 1.5 ? 0.5 - Math.abs(sw - 1)
    : 0;
}

function attr(emit, item) {
  emit('transform', translateItem(item));
}

function emitRectangle(emit, item) {
  var off = offset$1(item);
  emit('d', rectangle(null, item, off, off));
}

function background(emit, item) {
  emit('class', 'background');
  emitRectangle(emit, item);
}

function foreground(emit, item) {
  emit('class', 'foreground');
  if (item.strokeForeground) {
    emitRectangle(emit, item);
  } else {
    emit('d', '');
  }
}

function content(emit, item, renderer) {
  var url = item.clip ? clip$1(renderer, item, item) : null;
  emit('clip-path', url);
}

function bound(bounds, group) {
  if (!group.clip && group.items) {
    var items = group.items;
    for (var j=0, m=items.length; j<m; ++j) {
      bounds.union(items[j].bounds);
    }
  }

  if ((group.clip || group.width || group.height) && !group.noBound) {
    bounds.add(0, 0).add(group.width || 0, group.height || 0);
  }

  boundStroke(bounds, group);

  return bounds.translate(group.x || 0, group.y || 0);
}

function rectanglePath(context, group, x, y) {
  var off = offset$1(group);
  context.beginPath();
  rectangle(context, group, (x || 0) + off, (y || 0) + off);
}

var hitBackground = hitPath(rectanglePath);
var hitForeground = hitPath(rectanglePath, false);

function draw(context, scene, bounds) {
  var renderer = this;

  visit(scene, function(group) {
    var gx = group.x || 0,
        gy = group.y || 0,
        fore = group.strokeForeground,
        opacity = group.opacity == null ? 1 : group.opacity;

    // draw group background
    if ((group.stroke || group.fill) && opacity) {
      rectanglePath(context, group, gx, gy);
      if (group.fill && fill(context, group, opacity)) {
        context.fill();
      }
      if (group.stroke && !fore && stroke(context, group, opacity)) {
        context.stroke();
      }
    }

    // setup graphics context, set clip and bounds
    context.save();
    context.translate(gx, gy);
    if (group.clip) clipGroup(context, group);
    if (bounds) bounds.translate(-gx, -gy);

    // draw group contents
    visit(group, function(item) {
      renderer.draw(context, item, bounds);
    });

    // restore graphics context
    if (bounds) bounds.translate(gx, gy);
    context.restore();

    // draw group foreground
    if (fore && group.stroke && opacity) {
      rectanglePath(context, group, gx, gy);
      if (stroke(context, group, opacity)) {
        context.stroke();
      }
    }
  });
}

function pick$1(context, scene, x, y, gx, gy) {
  if (scene.bounds && !scene.bounds.contains(gx, gy) || !scene.items) {
    return null;
  }

  var handler = this,
      cx = x * context.pixelRatio,
      cy = y * context.pixelRatio;

  return pickVisit(scene, function(group) {
    var hit, fore, ix, dx, dy, dw, dh, b, c;

    // first hit test bounding box
    b = group.bounds;
    if (b && !b.contains(gx, gy)) return;

    // passed bounds check, test rectangular clip
    dx = group.x || 0;
    dy = group.y || 0;
    dw = dx + (group.width || 0);
    dh = dy + (group.height || 0);
    c = group.clip;
    if (c && (gx < dx || gx > dw || gy < dx || gy > dh)) return;

    // adjust coordinate system
    context.save();
    context.translate(dx, dy);
    dx = gx - dx;
    dy = gy - dy;

    // test background for rounded corner clip
    if (c && hasCornerRadius(group) && !hitBackground(context, group, cx, cy)) {
      context.restore();
      return null;
    }

    fore = group.strokeForeground;
    ix = scene.interactive !== false;

    // hit test against group foreground
    if (ix && fore && group.stroke
        && hitForeground(context, group, cx, cy)) {
      context.restore();
      return group;
    }

    // hit test against contained marks
    hit = pickVisit(group, function(mark) {
      return pickMark(mark, dx, dy)
        ? handler.pick(mark, x, y, dx, dy)
        : null;
    });

    // hit test against group background
    if (!hit && ix && (group.fill || (!fore && group.stroke))
        && hitBackground(context, group, cx, cy)) {
      hit = group;
    }

    // restore state and return
    context.restore();
    return hit || null;
  });
}

function pickMark(mark, x, y) {
  return (mark.interactive !== false || mark.marktype === 'group')
    && mark.bounds && mark.bounds.contains(x, y);
}

var group = {
  type:       'group',
  tag:        'g',
  nested:     false,
  attr:       attr,
  bound:      bound,
  draw:       draw,
  pick:       pick$1,
  isect:      intersectRect,
  content:    content,
  background: background,
  foreground: foreground
};

function getImage(item, renderer) {
  var image = item.image;
  if (!image || item.url && item.url !== image.url) {
    image = {complete: false, width: 0, height: 0};
    renderer.loadImage(item.url).then(image => {
      item.image = image;
      item.image.url = item.url;
    });
  }
  return image;
}

function imageWidth(item, image) {
  return item.width != null ? item.width
    : !image || !image.width ? 0
    : item.aspect !== false && item.height ? item.height * image.width / image.height
    : image.width;
}

function imageHeight(item, image) {
  return item.height != null ? item.height
    : !image || !image.height ? 0
    : item.aspect !== false && item.width ? item.width * image.height / image.width
    : image.height;
}

function imageXOffset(align, w) {
  return align === 'center' ? w / 2 : align === 'right' ? w : 0;
}

function imageYOffset(baseline, h) {
  return baseline === 'middle' ? h / 2 : baseline === 'bottom' ? h : 0;
}

function attr$1(emit, item, renderer) {
  var image = getImage(item, renderer),
      x = item.x || 0,
      y = item.y || 0,
      w = imageWidth(item, image),
      h = imageHeight(item, image),
      a = item.aspect === false ? 'none' : 'xMidYMid';

  x -= imageXOffset(item.align, w);
  y -= imageYOffset(item.baseline, h);

  if (!image.src && image.toDataURL) {
    emit('href', image.toDataURL(), 'http://www.w3.org/1999/xlink', 'xlink:href');
  } else {
    emit('href', image.src || '', 'http://www.w3.org/1999/xlink', 'xlink:href');
  }
  emit('transform', translate(x, y));
  emit('width', w);
  emit('height', h);
  emit('preserveAspectRatio', a);
}

function bound$1(bounds, item) {
  var image = item.image,
      x = item.x || 0,
      y = item.y || 0,
      w = imageWidth(item, image),
      h = imageHeight(item, image);

  x -= imageXOffset(item.align, w);
  y -= imageYOffset(item.baseline, h);

  return bounds.set(x, y, x + w, y + h);
}

function draw$1(context, scene, bounds) {
  var renderer = this;

  visit(scene, function(item) {
    if (bounds && !bounds.intersects(item.bounds)) return; // bounds check

    var image = getImage(item, renderer),
        x = item.x || 0,
        y = item.y || 0,
        w = imageWidth(item, image),
        h = imageHeight(item, image),
        opacity, ar0, ar1, t;

    x -= imageXOffset(item.align, w);
    y -= imageYOffset(item.baseline, h);

    if (item.aspect !== false) {
      ar0 = image.width / image.height;
      ar1 = item.width / item.height;
      if (ar0 === ar0 && ar1 === ar1 && ar0 !== ar1) {
        if (ar1 < ar0) {
          t = w / ar0;
          y += (h - t) / 2;
          h = t;
        } else {
          t = h * ar0;
          x += (w - t) / 2;
          w = t;
        }
      }
    }

    if (image.complete || image.toDataURL) {
      context.globalAlpha = (opacity = item.opacity) != null ? opacity : 1;
      context.imageSmoothingEnabled = item.smooth !== false;
      context.drawImage(image, x, y, w, h);
    }
  });
}

var image = {
  type:     'image',
  tag:      'image',
  nested:   false,
  attr:     attr$1,
  bound:    bound$1,
  draw:     draw$1,
  pick:     pick(),
  isect:    truthy, // bounds check is sufficient
  get:      getImage,
  xOffset:  imageXOffset,
  yOffset:  imageYOffset
};

var line$1 = markMultiItemPath('line', line, pickLine);

function attr$2(emit, item) {
  var sx = item.scaleX || 1,
      sy = item.scaleY || 1;
  if (sx !== 1 || sy !== 1) {
    emit('vector-effect', 'non-scaling-stroke');
  }
  emit('transform', transformItem(item));
  emit('d', item.path);
}

function path(context, item) {
  var path = item.path;
  if (path == null) return true;

  var x = item.x || 0,
      y = item.y || 0,
      sx = item.scaleX || 1,
      sy = item.scaleY || 1,
      a = (item.angle || 0) * DegToRad,
      cache = item.pathCache;

  if (!cache || cache.path !== path) {
    (item.pathCache = cache = pathParse(path)).path = path;
  }

  if (a && context.rotate && context.translate) {
    context.translate(x, y);
    context.rotate(a);
    pathRender(context, cache, 0, 0, sx, sy);
    context.rotate(-a);
    context.translate(-x, -y);
  } else {
    pathRender(context, cache, x, y, sx, sy);
  }
}

function bound$2(bounds, item) {
  path(context(bounds), item)
    ? bounds.set(0, 0, 0, 0)
    : boundStroke(bounds, item, true);

  if (item.angle) {
    bounds.rotate(item.angle * DegToRad, item.x || 0, item.y || 0);
  }

  return bounds;
}

var path$1 = {
  type:   'path',
  tag:    'path',
  nested: false,
  attr:   attr$2,
  bound:  bound$2,
  draw:   drawAll(path),
  pick:   pickPath(path),
  isect:  intersectPath(path)
};

function attr$3(emit, item) {
  emit('d', rectangle(null, item));
}

function bound$3(bounds, item) {
  var x, y;
  return boundStroke(bounds.set(
    x = item.x || 0,
    y = item.y || 0,
    (x + item.width) || 0,
    (y + item.height) || 0
  ), item);
}

function draw$2(context, item) {
  context.beginPath();
  rectangle(context, item);
}

var rect = {
  type:   'rect',
  tag:    'path',
  nested: false,
  attr:   attr$3,
  bound:  bound$3,
  draw:   drawAll(draw$2),
  pick:   pickPath(draw$2),
  isect:  intersectRect
};

function attr$4(emit, item) {
  emit('transform', translateItem(item));
  emit('x2', item.x2 != null ? item.x2 - (item.x || 0) : 0);
  emit('y2', item.y2 != null ? item.y2 - (item.y || 0) : 0);
}

function bound$4(bounds, item) {
  var x1, y1;
  return boundStroke(bounds.set(
    x1 = item.x || 0,
    y1 = item.y || 0,
    item.x2 != null ? item.x2 : x1,
    item.y2 != null ? item.y2 : y1
  ), item);
}

function path$2(context, item, opacity) {
  var x1, y1, x2, y2;

  if (item.stroke && stroke(context, item, opacity)) {
    x1 = item.x || 0;
    y1 = item.y || 0;
    x2 = item.x2 != null ? item.x2 : x1;
    y2 = item.y2 != null ? item.y2 : y1;
    context.beginPath();
    context.moveTo(x1, y1);
    context.lineTo(x2, y2);
    return true;
  }
  return false;
}

function draw$3(context, scene, bounds) {
  visit(scene, function(item) {
    if (bounds && !bounds.intersects(item.bounds)) return; // bounds check
    var opacity = item.opacity == null ? 1 : item.opacity;
    if (opacity && path$2(context, item, opacity)) {
      context.stroke();
    }
  });
}

function hit(context, item, x, y) {
  if (!context.isPointInStroke) return false;
  return path$2(context, item, 1) && context.isPointInStroke(x, y);
}

var rule = {
  type:   'rule',
  tag:    'line',
  nested: false,
  attr:   attr$4,
  bound:  bound$4,
  draw:   draw$3,
  pick:   pick(hit),
  isect:  intersectRule
};

var shape$1 = markItemPath('shape', shape);

var symbol$1 = markItemPath('symbol', symbol, intersectPoint);

var currFontHeight;

var textMetrics = {
  height: fontSize,
  measureWidth: measureWidth,
  estimateWidth: estimateWidth,
  width: estimateWidth,
  canvas: useCanvas
};

useCanvas(true);

// make dumb, simple estimate if no canvas is available
function estimateWidth(item, text) {
  currFontHeight = fontSize(item);
  return estimate(textValue(item, text));
}

function estimate(text) {
  return ~~(0.8 * text.length * currFontHeight);
}

// measure text width if canvas is available
function measureWidth(item, text) {
  return fontSize(item) <= 0 ? 0
    : (context$1.font = font(item), measure$1(textValue(item, text)));
}

function measure$1(text) {
  return context$1.measureText(text).width;
}

function fontSize(item) {
  return item.fontSize != null ? item.fontSize : 11;
}

function useCanvas(use) {
  textMetrics.width = (use && context$1) ? measureWidth : estimateWidth;
}

function lineHeight(item) {
  return item.lineHeight != null ? item.lineHeight : (fontSize(item) + 2);
}

function lineArray(_) {
  return isArray(_) ? _.length > 1 ? _ : _[0] : _;
}

function textLines(item) {
  return lineArray(
    item.lineBreak && item.text && !isArray(item.text)
      ? item.text.split(item.lineBreak)
      : item.text
  );
}

function multiLineOffset(item) {
  const tl = textLines(item);
  return (isArray(tl) ? (tl.length - 1) : 0) * lineHeight(item);
}

function textValue(item, line) {
  return line == null ? ''
    : item.limit > 0 ? truncate$1(item, line)
    : line + '';
}

function truncate$1(item, line) {
  var limit = +item.limit,
      text = line + '',
      width;

  if (textMetrics.width === measureWidth) {
    // we are using canvas
    context$1.font = font(item);
    width = measure$1;
  } else {
    // we are relying on estimates
    currFontHeight = fontSize(item);
    width = estimate;
  }

  if (width(text) < limit) return text;

  var ellipsis = item.ellipsis || '\u2026',
      rtl = item.dir === 'rtl',
      lo = 0,
      hi = text.length, mid;

  limit -= width(ellipsis);

  if (rtl) {
    while (lo < hi) {
      mid = (lo + hi >>> 1);
      if (width(text.slice(mid)) > limit) lo = mid + 1;
      else hi = mid;
    }
    return ellipsis + text.slice(lo);
  } else {
    while (lo < hi) {
      mid = 1 + (lo + hi >>> 1);
      if (width(text.slice(0, mid)) < limit) lo = mid;
      else hi = mid - 1;
    }
    return text.slice(0, lo) + ellipsis;
  }
}

function fontFamily(item, quote) {
  var font = item.font;
  return (quote && font
    ? String(font).replace(/"/g, '\'')
    : font) || 'sans-serif';
}

function font(item, quote) {
  return '' +
    (item.fontStyle ? item.fontStyle + ' ' : '') +
    (item.fontVariant ? item.fontVariant + ' ' : '') +
    (item.fontWeight ? item.fontWeight + ' ' : '') +
    fontSize(item) + 'px ' +
    fontFamily(item, quote);
}

function offset$2(item) {
  // perform our own font baseline calculation
  // why? not all browsers support SVG 1.1 'alignment-baseline' :(
  var baseline = item.baseline,
      h = fontSize(item);
  return Math.round(
    baseline === 'top'    ?  0.79*h :
    baseline === 'middle' ?  0.30*h :
    baseline === 'bottom' ? -0.21*h : 0
  );
}

var textAlign = {
  'left':   'start',
  'center': 'middle',
  'right':  'end'
};

var tempBounds = new Bounds();

function anchorPoint(item) {
  var x = item.x || 0,
      y = item.y || 0,
      r = item.radius || 0, t;

  if (r) {
    t = (item.theta || 0) - HalfPi;
    x += r * Math.cos(t);
    y += r * Math.sin(t);
  }

  tempBounds.x1 = x;
  tempBounds.y1 = y;
  return tempBounds;
}

function attr$5(emit, item) {
  var dx = item.dx || 0,
      dy = (item.dy || 0) + offset$2(item),
      p = anchorPoint(item),
      x = p.x1,
      y = p.y1,
      a = item.angle || 0, t;

  emit('text-anchor', textAlign[item.align] || 'start');

  if (a) {
    t = translate(x, y) + ' ' + rotate(a);
    if (dx || dy) t += ' ' + translate(dx, dy);
  } else {
    t = translate(x + dx, y + dy);
  }
  emit('transform', t);
}

function bound$5(bounds, item, mode) {
  var h = textMetrics.height(item),
      a = item.align,
      p = anchorPoint(item),
      x = p.x1,
      y = p.y1,
      dx = item.dx || 0,
      dy = (item.dy || 0) + offset$2(item) - Math.round(0.8*h), // use 4/5 offset
      tl = textLines(item),
      w;

  // get dimensions
  if (isArray(tl)) {
    // multi-line text
    h += lineHeight(item) * (tl.length - 1);
    w = tl.reduce((w, t) => Math.max(w, textMetrics.width(item, t)), 0);
  } else {
    // single-line text
    w = textMetrics.width(item, tl);
  }

  // horizontal alignment
  if (a === 'center') {
    dx -= (w / 2);
  } else if (a === 'right') {
    dx -= w;
  }

  bounds.set(dx+=x, dy+=y, dx+w, dy+h);

  if (item.angle && !mode) {
    bounds.rotate(item.angle * DegToRad, x, y);
  } else if (mode === 2) {
    return bounds.rotatedPoints(item.angle * DegToRad, x, y);
  }
  return bounds;
}

function draw$4(context, scene, bounds) {
  visit(scene, function(item) {
    var opacity = item.opacity == null ? 1 : item.opacity,
        p, x, y, i, lh, tl, str;

    if (bounds && !bounds.intersects(item.bounds) || // bounds check
        opacity === 0 || item.fontSize <= 0 ||
        item.text == null || item.text.length === 0) return;

    context.font = font(item);
    context.textAlign = item.align || 'left';

    p = anchorPoint(item);
    x = p.x1,
    y = p.y1;

    if (item.angle) {
      context.save();
      context.translate(x, y);
      context.rotate(item.angle * DegToRad);
      x = y = 0; // reset x, y
    }
    x += (item.dx || 0);
    y += (item.dy || 0) + offset$2(item);

    tl = textLines(item);
    if (isArray(tl)) {
      lh = lineHeight(item);
      for (i=0; i<tl.length; ++i) {
        str = textValue(item, tl[i]);
        if (item.fill && fill(context, item, opacity)) {
          context.fillText(str, x, y);
        }
        if (item.stroke && stroke(context, item, opacity)) {
          context.strokeText(str, x, y);
        }
        y += lh;
      }
    } else {
      str = textValue(item, tl);
      if (item.fill && fill(context, item, opacity)) {
        context.fillText(str, x, y);
      }
      if (item.stroke && stroke(context, item, opacity)) {
        context.strokeText(str, x, y);
      }
    }

    if (item.angle) context.restore();
  });
}

function hit$1(context, item, x, y, gx, gy) {
  if (item.fontSize <= 0) return false;
  if (!item.angle) return true; // bounds sufficient if no rotation

  // project point into space of unrotated bounds
  var p = anchorPoint(item),
      ax = p.x1,
      ay = p.y1,
      b = bound$5(tempBounds, item, 1),
      a = -item.angle * DegToRad,
      cos = Math.cos(a),
      sin = Math.sin(a),
      px = cos * gx - sin * gy + (ax - cos * ax + sin * ay),
      py = sin * gx + cos * gy + (ay - sin * ax - cos * ay);

  return b.contains(px, py);
}

function intersectText(item, box) {
  var p = bound$5(tempBounds, item, 2);
  return intersectBoxLine(box, p[0], p[1], p[2], p[3])
      || intersectBoxLine(box, p[0], p[1], p[4], p[5])
      || intersectBoxLine(box, p[4], p[5], p[6], p[7])
      || intersectBoxLine(box, p[2], p[3], p[6], p[7]);
}

var text = {
  type:   'text',
  tag:    'text',
  nested: false,
  attr:   attr$5,
  bound:  bound$5,
  draw:   draw$4,
  pick:   pick(hit$1),
  isect:  intersectText
};

var trail$1 = markMultiItemPath('trail', trail, pickTrail);

var Marks = {
  arc:     arc$1,
  area:    area$1,
  group:   group,
  image:   image,
  line:    line$1,
  path:    path$1,
  rect:    rect,
  rule:    rule,
  shape:   shape$1,
  symbol:  symbol$1,
  text:    text,
  trail:   trail$1
};

function boundItem(item, func, opt) {
  var type = Marks[item.mark.marktype],
      bound = func || type.bound;
  if (type.nested) item = item.mark;

  return bound(item.bounds || (item.bounds = new Bounds()), item, opt);
}

var DUMMY = {mark: null};

function boundMark(mark, bounds, opt) {
  var type  = Marks[mark.marktype],
      bound = type.bound,
      items = mark.items,
      hasItems = items && items.length,
      i, n, item, b;

  if (type.nested) {
    if (hasItems) {
      item = items[0];
    } else {
      // no items, fake it
      DUMMY.mark = mark;
      item = DUMMY;
    }
    b = boundItem(item, bound, opt);
    bounds = bounds && bounds.union(b) || b;
    return bounds;
  }

  bounds = bounds
    || mark.bounds && mark.bounds.clear()
    || new Bounds();

  if (hasItems) {
    for (i=0, n=items.length; i<n; ++i) {
      bounds.union(boundItem(items[i], bound, opt));
    }
  }

  return mark.bounds = bounds;
}

var keys = [
  'marktype', 'name', 'role', 'interactive', 'clip', 'items', 'zindex',
  'x', 'y', 'width', 'height', 'align', 'baseline',             // layout
  'fill', 'fillOpacity', 'opacity',                             // fill
  'stroke', 'strokeOpacity', 'strokeWidth', 'strokeCap',        // stroke
  'strokeDash', 'strokeDashOffset',                             // stroke dash
  'strokeForeground', 'strokeOffset',                           // group
  'startAngle', 'endAngle', 'innerRadius', 'outerRadius',       // arc
  'cornerRadius', 'padAngle',                                   // arc, rect
  'cornerRadiusTopLeft', 'cornerRadiusTopRight',                // rect, group
  'cornerRadiusBottomLeft', 'cornerRadiusBottomRight',
  'interpolate', 'tension', 'orient', 'defined',                // area, line
  'url', 'aspect', 'smooth',                                    // image
  'path', 'scaleX', 'scaleY',                                   // path
  'x2', 'y2',                                                   // rule
  'size', 'shape',                                              // symbol
  'text', 'angle', 'theta', 'radius', 'dir', 'dx', 'dy',        // text
  'ellipsis', 'limit', 'lineBreak', 'lineHeight',
  'font', 'fontSize', 'fontWeight', 'fontStyle', 'fontVariant'  // font
];

function sceneToJSON(scene, indent) {
  return JSON.stringify(scene, keys, indent);
}

function sceneFromJSON(json) {
  var scene = (typeof json === 'string' ? JSON.parse(json) : json);
  return initialize(scene);
}

function initialize(scene) {
  var type = scene.marktype,
      items = scene.items,
      parent, i, n;

  if (items) {
    for (i=0, n=items.length; i<n; ++i) {
      parent = type ? 'mark' : 'group';
      items[i][parent] = scene;
      if (items[i].zindex) items[i][parent].zdirty = true;
      if ('group' === (type || parent)) initialize(items[i]);
    }
  }

  if (type) boundMark(scene);
  return scene;
}

function Scenegraph(scene) {
  if (arguments.length) {
    this.root = sceneFromJSON(scene);
  } else {
    this.root = createMark({
      marktype: 'group',
      name: 'root',
      role: 'frame'
    });
    this.root.items = [new GroupItem(this.root)];
  }
}

var prototype$I = Scenegraph.prototype;

prototype$I.toJSON = function(indent) {
  return sceneToJSON(this.root, indent || 0);
};

prototype$I.mark = function(markdef, group, index) {
  group = group || this.root.items[0];
  var mark = createMark(markdef, group);
  group.items[index] = mark;
  if (mark.zindex) mark.group.zdirty = true;
  return mark;
};

function createMark(def, group) {
  return {
    bounds:      new Bounds(),
    clip:        !!def.clip,
    group:       group,
    interactive: def.interactive === false ? false : true,
    items:       [],
    marktype:    def.marktype,
    name:        def.name || undefined,
    role:        def.role || undefined,
    zindex:      def.zindex || 0
  };
}

// create a new DOM element
function domCreate(doc, tag, ns) {
  if (!doc && typeof document !== 'undefined' && document.createElement) {
    doc = document;
  }
  return doc
    ? (ns ? doc.createElementNS(ns, tag) : doc.createElement(tag))
    : null;
}

// find first child element with matching tag
function domFind(el, tag) {
  tag = tag.toLowerCase();
  var nodes = el.childNodes, i = 0, n = nodes.length;
  for (; i<n; ++i) if (nodes[i].tagName.toLowerCase() === tag) {
    return nodes[i];
  }
}

// retrieve child element at given index
// create & insert if doesn't exist or if tags do not match
function domChild(el, index, tag, ns) {
  var a = el.childNodes[index], b;
  if (!a || a.tagName.toLowerCase() !== tag.toLowerCase()) {
    b = a || null;
    a = domCreate(el.ownerDocument, tag, ns);
    el.insertBefore(a, b);
  }
  return a;
}

// remove all child elements at or above the given index
function domClear(el, index) {
  var nodes = el.childNodes,
      curr = nodes.length;
  while (curr > index) el.removeChild(nodes[--curr]);
  return el;
}

// generate css class name for mark
function cssClass(mark) {
  return 'mark-' + mark.marktype
    + (mark.role ? ' role-' + mark.role : '')
    + (mark.name ? ' ' + mark.name : '');
}

function point(event, el) {
  var rect = el.getBoundingClientRect();
  return [
    event.clientX - rect.left - (el.clientLeft || 0),
    event.clientY - rect.top - (el.clientTop || 0)
  ];
}

function resolveItem(item, event, el, origin) {
  var mark = item && item.mark,
      mdef, p;

  if (mark && (mdef = Marks[mark.marktype]).tip) {
    p = point(event, el);
    p[0] -= origin[0];
    p[1] -= origin[1];
    while (item = item.mark.group) {
      p[0] -= item.x || 0;
      p[1] -= item.y || 0;
    }
    item = mdef.tip(mark.items, p);
  }

  return item;
}

/**
 * Create a new Handler instance.
 * @param {object} [customLoader] - Optional loader instance for
 *   href URL sanitization. If not specified, a standard loader
 *   instance will be generated.
 * @param {function} [customTooltip] - Optional tooltip handler
 *   function for custom tooltip display.
 * @constructor
 */
function Handler(customLoader, customTooltip) {
  this._active = null;
  this._handlers = {};
  this._loader = customLoader || loader();
  this._tooltip = customTooltip || defaultTooltip;
}

// The default tooltip display handler.
// Sets the HTML title attribute on the visualization container.
function defaultTooltip(handler, event, item, value) {
  handler.element().setAttribute('title', value || '');
}

var prototype$J = Handler.prototype;

/**
 * Initialize a new Handler instance.
 * @param {DOMElement} el - The containing DOM element for the display.
 * @param {Array<number>} origin - The origin of the display, in pixels.
 *   The coordinate system will be translated to this point.
 * @param {object} [obj] - Optional context object that should serve as
 *   the "this" context for event callbacks.
 * @return {Handler} - This handler instance.
 */
prototype$J.initialize = function(el, origin, obj) {
  this._el = el;
  this._obj = obj || null;
  return this.origin(origin);
};

/**
 * Returns the parent container element for a visualization.
 * @return {DOMElement} - The containing DOM element.
 */
prototype$J.element = function() {
  return this._el;
};

/**
 * Returns the scene element (e.g., canvas or SVG) of the visualization
 * Subclasses must override if the first child is not the scene element.
 * @return {DOMElement} - The scene (e.g., canvas or SVG) element.
 */
prototype$J.canvas = function() {
  return this._el && this._el.firstChild;
};

/**
 * Get / set the origin coordinates of the visualization.
 */
prototype$J.origin = function(origin) {
  if (arguments.length) {
    this._origin = origin || [0, 0];
    return this;
  } else {
    return this._origin.slice();
  }
};

/**
 * Get / set the scenegraph root.
 */
prototype$J.scene = function(scene) {
  if (!arguments.length) return this._scene;
  this._scene = scene;
  return this;
};

/**
 * Add an event handler. Subclasses should override this method.
 */
prototype$J.on = function(/*type, handler*/) {};

/**
 * Remove an event handler. Subclasses should override this method.
 */
prototype$J.off = function(/*type, handler*/) {};

/**
 * Utility method for finding the array index of an event handler.
 * @param {Array} h - An array of registered event handlers.
 * @param {string} type - The event type.
 * @param {function} handler - The event handler instance to find.
 * @return {number} - The handler's array index or -1 if not registered.
 */
prototype$J._handlerIndex = function(h, type, handler) {
  for (var i = h ? h.length : 0; --i>=0;) {
    if (h[i].type === type && (!handler || h[i].handler === handler)) {
      return i;
    }
  }
  return -1;
};

/**
 * Returns an array with registered event handlers.
 * @param {string} [type] - The event type to query. Any annotations
 *   are ignored; for example, for the argument "click.foo", ".foo" will
 *   be ignored and the method returns all "click" handlers. If type is
 *   null or unspecified, this method returns handlers for all types.
 * @return {Array} - A new array containing all registered event handlers.
 */
prototype$J.handlers = function(type) {
  var h = this._handlers, a = [], k;
  if (type) {
    a.push.apply(a, h[this.eventName(type)]);
  } else {
    for (k in h) { a.push.apply(a, h[k]); }
  }
  return a;
};

/**
 * Parses an event name string to return the specific event type.
 * For example, given "click.foo" returns "click"
 * @param {string} name - The input event type string.
 * @return {string} - A string with the event type only.
 */
prototype$J.eventName = function(name) {
  var i = name.indexOf('.');
  return i < 0 ? name : name.slice(0,i);
};

/**
 * Handle hyperlink navigation in response to an item.href value.
 * @param {Event} event - The event triggering hyperlink navigation.
 * @param {Item} item - The scenegraph item.
 * @param {string} href - The URL to navigate to.
 */
prototype$J.handleHref = function(event, item, href) {
  this._loader
    .sanitize(href, {context:'href'})
    .then(function(opt) {
      var e = new MouseEvent(event.type, event),
          a = domCreate(null, 'a');
      for (var name in opt) a.setAttribute(name, opt[name]);
      a.dispatchEvent(e);
    })
    .catch(function() { /* do nothing */ });
};

/**
 * Handle tooltip display in response to an item.tooltip value.
 * @param {Event} event - The event triggering tooltip display.
 * @param {Item} item - The scenegraph item.
 * @param {boolean} show - A boolean flag indicating whether
 *   to show or hide a tooltip for the given item.
 */
prototype$J.handleTooltip = function(event, item, show) {
  if (item && item.tooltip != null) {
    item = resolveItem(item, event, this.canvas(), this._origin);
    var value = (show && item && item.tooltip) || null;
    this._tooltip.call(this._obj, this, event, item, value);
  }
};

/**
 * Returns the size of a scenegraph item and its position relative
 * to the viewport.
 * @param {Item} item - The scenegraph item.
 * @return {object} - A bounding box object (compatible with the
 *   DOMRect type) consisting of x, y, width, heigh, top, left,
 *   right, and bottom properties.
 */
prototype$J.getItemBoundingClientRect = function(item) {
  if (!(el = this.canvas())) return;

  var el, rect = el.getBoundingClientRect(),
      origin = this._origin,
      itemBounds = item.bounds,
      x = itemBounds.x1 + origin[0] + rect.left,
      y = itemBounds.y1 + origin[1] + rect.top,
      w = itemBounds.width(),
      h = itemBounds.height();

  // translate coordinate for each parent group
  while (item.mark && (item = item.mark.group)) {
    x += item.x || 0;
    y += item.y || 0;
  }

  // return DOMRect-compatible bounding box
  return {
    x:      x,
    y:      y,
    width:  w,
    height: h,
    left:   x,
    top:    y,
    right:  x + w,
    bottom: y + h
  };
};

/**
 * Create a new Renderer instance.
 * @param {object} [loader] - Optional loader instance for
 *   image and href URL sanitization. If not specified, a
 *   standard loader instance will be generated.
 * @constructor
 */
function Renderer(loader) {
  this._el = null;
  this._bgcolor = null;
  this._loader = new ResourceLoader(loader);
}

var prototype$K = Renderer.prototype;

/**
 * Initialize a new Renderer instance.
 * @param {DOMElement} el - The containing DOM element for the display.
 * @param {number} width - The coordinate width of the display, in pixels.
 * @param {number} height - The coordinate height of the display, in pixels.
 * @param {Array<number>} origin - The origin of the display, in pixels.
 *   The coordinate system will be translated to this point.
 * @param {number} [scaleFactor=1] - Optional scaleFactor by which to multiply
 *   the width and height to determine the final pixel size.
 * @return {Renderer} - This renderer instance.
 */
prototype$K.initialize = function(el, width, height, origin, scaleFactor) {
  this._el = el;
  return this.resize(width, height, origin, scaleFactor);
};

/**
 * Returns the parent container element for a visualization.
 * @return {DOMElement} - The containing DOM element.
 */
prototype$K.element = function() {
  return this._el;
};

/**
 * Returns the scene element (e.g., canvas or SVG) of the visualization
 * Subclasses must override if the first child is not the scene element.
 * @return {DOMElement} - The scene (e.g., canvas or SVG) element.
 */
prototype$K.canvas = function() {
  return this._el && this._el.firstChild;
};

/**
 * Get / set the background color.
 */
prototype$K.background = function(bgcolor) {
  if (arguments.length === 0) return this._bgcolor;
  this._bgcolor = bgcolor;
  return this;
};

/**
 * Resize the display.
 * @param {number} width - The new coordinate width of the display, in pixels.
 * @param {number} height - The new coordinate height of the display, in pixels.
 * @param {Array<number>} origin - The new origin of the display, in pixels.
 *   The coordinate system will be translated to this point.
 * @param {number} [scaleFactor=1] - Optional scaleFactor by which to multiply
 *   the width and height to determine the final pixel size.
 * @return {Renderer} - This renderer instance;
 */
prototype$K.resize = function(width, height, origin, scaleFactor) {
  this._width = width;
  this._height = height;
  this._origin = origin || [0, 0];
  this._scale = scaleFactor || 1;
  return this;
};

/**
 * Report a dirty item whose bounds should be redrawn.
 * This base class method does nothing. Subclasses that perform
 * incremental should implement this method.
 * @param {Item} item - The dirty item whose bounds should be redrawn.
 */
prototype$K.dirty = function(/*item*/) {
};

/**
 * Render an input scenegraph, potentially with a set of dirty items.
 * This method will perform an immediate rendering with available resources.
 * The renderer may also need to perform image loading to perform a complete
 * render. This process can lead to asynchronous re-rendering of the scene
 * after this method returns. To receive notification when rendering is
 * complete, use the renderAsync method instead.
 * @param {object} scene - The root mark of a scenegraph to render.
 * @return {Renderer} - This renderer instance.
 */
prototype$K.render = function(scene) {
  var r = this;

  // bind arguments into a render call, and cache it
  // this function may be subsequently called for async redraw
  r._call = function() { r._render(scene); };

  // invoke the renderer
  r._call();

  // clear the cached call for garbage collection
  // async redraws will stash their own copy
  r._call = null;

  return r;
};

/**
 * Internal rendering method. Renderer subclasses should override this
 * method to actually perform rendering.
 * @param {object} scene - The root mark of a scenegraph to render.
 */
prototype$K._render = function(/*scene*/) {
  // subclasses to override
};

/**
 * Asynchronous rendering method. Similar to render, but returns a Promise
 * that resolves when all rendering is completed. Sometimes a renderer must
 * perform image loading to get a complete rendering. The returned
 * Promise will not resolve until this process completes.
 * @param {object} scene - The root mark of a scenegraph to render.
 * @return {Promise} - A Promise that resolves when rendering is complete.
 */
prototype$K.renderAsync = function(scene) {
  var r = this.render(scene);
  return this._ready
    ? this._ready.then(function() { return r; })
    : Promise.resolve(r);
};

/**
 * Internal method for asynchronous resource loading.
 * Proxies method calls to the ImageLoader, and tracks loading
 * progress to invoke a re-render once complete.
 * @param {string} method - The method name to invoke on the ImageLoader.
 * @param {string} uri - The URI for the requested resource.
 * @return {Promise} - A Promise that resolves to the requested resource.
 */
prototype$K._load = function(method, uri) {
  var r = this,
      p = r._loader[method](uri);

  if (!r._ready) {
    // re-render the scene when loading completes
    var call = r._call;
    r._ready = r._loader.ready()
      .then(function(redraw) {
        if (redraw) call();
        r._ready = null;
      });
  }

  return p;
};

/**
 * Sanitize a URL to include as a hyperlink in the rendered scene.
 * This method proxies a call to ImageLoader.sanitizeURL, but also tracks
 * image loading progress and invokes a re-render once complete.
 * @param {string} uri - The URI string to sanitize.
 * @return {Promise} - A Promise that resolves to the sanitized URL.
 */
prototype$K.sanitizeURL = function(uri) {
  return this._load('sanitizeURL', uri);
};

/**
 * Requests an image to include in the rendered scene.
 * This method proxies a call to ImageLoader.loadImage, but also tracks
 * image loading progress and invokes a re-render once complete.
 * @param {string} uri - The URI string of the image.
 * @return {Promise} - A Promise that resolves to the loaded Image.
 */
prototype$K.loadImage = function(uri) {
  return this._load('loadImage', uri);
};

var Events = [
  'keydown',
  'keypress',
  'keyup',
  'dragenter',
  'dragleave',
  'dragover',
  'mousedown',
  'mouseup',
  'mousemove',
  'mouseout',
  'mouseover',
  'click',
  'dblclick',
  'wheel',
  'mousewheel',
  'touchstart',
  'touchmove',
  'touchend'
];

var TooltipShowEvent = 'mousemove';

var TooltipHideEvent = 'mouseout';

var HrefEvent = 'click';

function CanvasHandler(loader, tooltip) {
  Handler.call(this, loader, tooltip);
  this._down = null;
  this._touch = null;
  this._first = true;
}

var prototype$L = inherits(CanvasHandler, Handler);

prototype$L.initialize = function(el, origin, obj) {
  // add event listeners
  var canvas = this._canvas = el && domFind(el, 'canvas');
  if (canvas) {
    var that = this;
    this.events.forEach(function(type) {
      canvas.addEventListener(type, function(evt) {
        if (prototype$L[type]) {
          prototype$L[type].call(that, evt);
        } else {
          that.fire(type, evt);
        }
      });
    });
  }

  return Handler.prototype.initialize.call(this, el, origin, obj);
};

// return the backing canvas instance
prototype$L.canvas = function() {
  return this._canvas;
};

// retrieve the current canvas context
prototype$L.context = function() {
  return this._canvas.getContext('2d');
};

// supported events
prototype$L.events = Events;

// to keep old versions of firefox happy
prototype$L.DOMMouseScroll = function(evt) {
  this.fire('mousewheel', evt);
};

function move(moveEvent, overEvent, outEvent) {
  return function(evt) {
    var a = this._active,
        p = this.pickEvent(evt);

    if (p === a) {
      // active item and picked item are the same
      this.fire(moveEvent, evt); // fire move
    } else {
      // active item and picked item are different
      if (!a || !a.exit) {
        // fire out for prior active item
        // suppress if active item was removed from scene
        this.fire(outEvent, evt);
      }
      this._active = p;          // set new active item
      this.fire(overEvent, evt); // fire over for new active item
      this.fire(moveEvent, evt); // fire move for new active item
    }
  };
}

function inactive(type) {
  return function(evt) {
    this.fire(type, evt);
    this._active = null;
  };
}

prototype$L.mousemove = move('mousemove', 'mouseover', 'mouseout');
prototype$L.dragover  = move('dragover', 'dragenter', 'dragleave');

prototype$L.mouseout  = inactive('mouseout');
prototype$L.dragleave = inactive('dragleave');

prototype$L.mousedown = function(evt) {
  this._down = this._active;
  this.fire('mousedown', evt);
};

prototype$L.click = function(evt) {
  if (this._down === this._active) {
    this.fire('click', evt);
    this._down = null;
  }
};

prototype$L.touchstart = function(evt) {
  this._touch = this.pickEvent(evt.changedTouches[0]);

  if (this._first) {
    this._active = this._touch;
    this._first = false;
  }

  this.fire('touchstart', evt, true);
};

prototype$L.touchmove = function(evt) {
  this.fire('touchmove', evt, true);
};

prototype$L.touchend = function(evt) {
  this.fire('touchend', evt, true);
  this._touch = null;
};

// fire an event
prototype$L.fire = function(type, evt, touch) {
  var a = touch ? this._touch : this._active,
      h = this._handlers[type], i, len;

  // set event type relative to scenegraph items
  evt.vegaType = type;

  // handle hyperlinks and tooltips first
  if (type === HrefEvent && a && a.href) {
    this.handleHref(evt, a, a.href);
  } else if (type === TooltipShowEvent || type === TooltipHideEvent) {
    this.handleTooltip(evt, a, type !== TooltipHideEvent);
  }

  // invoke all registered handlers
  if (h) {
    for (i=0, len=h.length; i<len; ++i) {
      h[i].handler.call(this._obj, evt, a);
    }
  }
};

// add an event handler
prototype$L.on = function(type, handler) {
  var name = this.eventName(type),
      h = this._handlers,
      i = this._handlerIndex(h[name], type, handler);

  if (i < 0) {
    (h[name] || (h[name] = [])).push({
      type:    type,
      handler: handler
    });
  }

  return this;
};

// remove an event handler
prototype$L.off = function(type, handler) {
  var name = this.eventName(type),
      h = this._handlers[name],
      i = this._handlerIndex(h, type, handler);

  if (i >= 0) {
    h.splice(i, 1);
  }

  return this;
};

prototype$L.pickEvent = function(evt) {
  var p = point(evt, this._canvas),
      o = this._origin;
  return this.pick(this._scene, p[0], p[1], p[0] - o[0], p[1] - o[1]);
};

// find the scenegraph item at the current mouse position
// x, y -- the absolute x, y mouse coordinates on the canvas element
// gx, gy -- the relative coordinates within the current group
prototype$L.pick = function(scene, x, y, gx, gy) {
  var g = this.context(),
      mark = Marks[scene.marktype];
  return mark.pick.call(this, g, scene, x, y, gx, gy);
};

function devicePixelRatio() {
  return typeof window !== 'undefined' ? window.devicePixelRatio || 1 : 1;
}

var pixelRatio = devicePixelRatio();

function resize(canvas, width, height, origin, scaleFactor, opt) {
  var inDOM = typeof HTMLElement !== 'undefined'
    && canvas instanceof HTMLElement
    && canvas.parentNode != null;

  var context = canvas.getContext('2d'),
      ratio = inDOM ? pixelRatio : scaleFactor,
      key;

  canvas.width = width * ratio;
  canvas.height = height * ratio;

  for (key in opt) {
    context[key] = opt[key];
  }

  if (inDOM && ratio !== 1) {
    canvas.style.width = width + 'px';
    canvas.style.height = height + 'px';
  }

  context.pixelRatio = ratio;
  context.setTransform(
    ratio, 0, 0, ratio,
    ratio * origin[0],
    ratio * origin[1]
  );

  return canvas;
}

function CanvasRenderer(loader) {
  Renderer.call(this, loader);
  this._redraw = false;
  this._dirty = new Bounds();
}

var prototype$M = inherits(CanvasRenderer, Renderer),
    base = Renderer.prototype,
    tempBounds$1 = new Bounds();

prototype$M.initialize = function(el, width, height, origin, scaleFactor, options) {
  this._options = options;
  this._canvas = domCanvas(1, 1, options && options.type); // instantiate a small canvas

  if (el) {
    domClear(el, 0).appendChild(this._canvas);
    this._canvas.setAttribute('class', 'marks');
  }
  // this method will invoke resize to size the canvas appropriately
  return base.initialize.call(this, el, width, height, origin, scaleFactor);
};

prototype$M.resize = function(width, height, origin, scaleFactor) {
  base.resize.call(this, width, height, origin, scaleFactor);
  resize(this._canvas, this._width, this._height,
    this._origin, this._scale, this._options && this._options.context);
  this._redraw = true;
  return this;
};

prototype$M.canvas = function() {
  return this._canvas;
};

prototype$M.context = function() {
  return this._canvas ? this._canvas.getContext('2d') : null;
};

prototype$M.dirty = function(item) {
  var b = translate$1(item.bounds, item.mark.group);
  this._dirty.union(b);
};

function clipToBounds(g, b, origin) {
  // expand bounds by 1 pixel, then round to pixel boundaries
  b.expand(1).round();

  // to avoid artifacts translate if origin has fractional pixels
  b.translate(-(origin[0] % 1), -(origin[1] % 1));

  // set clipping path
  g.beginPath();
  g.rect(b.x1, b.y1, b.width(), b.height());
  g.clip();

  return b;
}

function viewBounds(origin, width, height) {
  return tempBounds$1
    .set(0, 0, width, height)
    .translate(-origin[0], -origin[1]);
}

function translate$1(bounds, group) {
  if (group == null) return bounds;
  var b = tempBounds$1.clear().union(bounds);
  for (; group != null; group = group.mark.group) {
    b.translate(group.x || 0, group.y || 0);
  }
  return b;
}

prototype$M._render = function(scene) {
  var g = this.context(),
      o = this._origin,
      w = this._width,
      h = this._height,
      b = this._dirty;

  // setup
  g.save();
  if (this._redraw || b.empty()) {
    this._redraw = false;
    b = viewBounds(o, w, h).expand(1);
  } else {
    b = clipToBounds(g, b.intersect(viewBounds(o, w, h)), o);
  }

  this.clear(-o[0], -o[1], w, h);

  // render
  this.draw(g, scene, b);

  // takedown
  g.restore();

  this._dirty.clear();
  return this;
};

prototype$M.draw = function(ctx, scene, bounds) {
  var mark = Marks[scene.marktype];
  if (scene.clip) clip(ctx, scene);
  mark.draw.call(this, ctx, scene, bounds);
  if (scene.clip) ctx.restore();
};

prototype$M.clear = function(x, y, w, h) {
  var g = this.context();
  g.clearRect(x, y, w, h);
  if (this._bgcolor != null) {
    g.fillStyle = this._bgcolor;
    g.fillRect(x, y, w, h);
  }
};

function SVGHandler(loader, tooltip) {
  Handler.call(this, loader, tooltip);
  var h = this;
  h._hrefHandler = listener(h, function(evt, item) {
    if (item && item.href) h.handleHref(evt, item, item.href);
  });
  h._tooltipHandler = listener(h, function(evt, item) {
    h.handleTooltip(evt, item, evt.type !== TooltipHideEvent);
  });
}

var prototype$N = inherits(SVGHandler, Handler);

prototype$N.initialize = function(el, origin, obj) {
  var svg = this._svg;
  if (svg) {
    svg.removeEventListener(HrefEvent, this._hrefHandler);
    svg.removeEventListener(TooltipShowEvent, this._tooltipHandler);
    svg.removeEventListener(TooltipHideEvent, this._tooltipHandler);
  }
  this._svg = svg = el && domFind(el, 'svg');
  if (svg) {
    svg.addEventListener(HrefEvent, this._hrefHandler);
    svg.addEventListener(TooltipShowEvent, this._tooltipHandler);
    svg.addEventListener(TooltipHideEvent, this._tooltipHandler);
  }
  return Handler.prototype.initialize.call(this, el, origin, obj);
};

prototype$N.canvas = function() {
  return this._svg;
};

// wrap an event listener for the SVG DOM
function listener(context, handler) {
  return function(evt) {
    var target = evt.target,
        item = target.__data__;
    evt.vegaType = evt.type;
    item = Array.isArray(item) ? item[0] : item;
    handler.call(context._obj, evt, item);
  };
}

// add an event handler
prototype$N.on = function(type, handler) {
  var name = this.eventName(type),
      h = this._handlers,
      i = this._handlerIndex(h[name], type, handler);

  if (i < 0) {
    var x = {
      type:     type,
      handler:  handler,
      listener: listener(this, handler)
    };

    (h[name] || (h[name] = [])).push(x);
    if (this._svg) {
      this._svg.addEventListener(name, x.listener);
    }
  }

  return this;
};

// remove an event handler
prototype$N.off = function(type, handler) {
  var name = this.eventName(type),
      h = this._handlers[name],
      i = this._handlerIndex(h, type, handler);

  if (i >= 0) {
    if (this._svg) {
      this._svg.removeEventListener(name, h[i].listener);
    }
    h.splice(i, 1);
  }

  return this;
};

// generate string for an opening xml tag
// tag: the name of the xml tag
// attr: hash of attribute name-value pairs to include
// raw: additional raw string to include in tag markup
function openTag(tag, attr, raw) {
  var s = '<' + tag, key, val;
  if (attr) {
    for (key in attr) {
      val = attr[key];
      if (val != null) {
        s += ' ' + key + '="' + val + '"';
      }
    }
  }
  if (raw) s += ' ' + raw;
  return s + '>';
}

// generate string for closing xml tag
// tag: the name of the xml tag
function closeTag(tag) {
  return '</' + tag + '>';
}

var metadata = {
  'version': '1.1',
  'xmlns': 'http://www.w3.org/2000/svg',
  'xmlns:xlink': 'http://www.w3.org/1999/xlink'
};

var styles = {
  'fill':             'fill',
  'fillOpacity':      'fill-opacity',
  'stroke':           'stroke',
  'strokeOpacity':    'stroke-opacity',
  'strokeWidth':      'stroke-width',
  'strokeCap':        'stroke-linecap',
  'strokeJoin':       'stroke-linejoin',
  'strokeDash':       'stroke-dasharray',
  'strokeDashOffset': 'stroke-dashoffset',
  'strokeMiterLimit': 'stroke-miterlimit',
  'opacity':          'opacity'
};

var styleProperties = Object.keys(styles);

var ns = metadata.xmlns;

function SVGRenderer(loader) {
  Renderer.call(this, loader);
  this._dirtyID = 0;
  this._dirty = [];
  this._svg = null;
  this._root = null;
  this._defs = null;
}

var prototype$O = inherits(SVGRenderer, Renderer);
var base$1 = Renderer.prototype;

prototype$O.initialize = function(el, width, height, padding) {
  if (el) {
    this._svg = domChild(el, 0, 'svg', ns);
    this._svg.setAttribute('class', 'marks');
    domClear(el, 1);
    // set the svg root group
    this._root = domChild(this._svg, 0, 'g', ns);
    domClear(this._svg, 1);
  }

  // create the svg definitions cache
  this._defs = {
    gradient: {},
    clipping: {}
  };

  // set background color if defined
  this.background(this._bgcolor);

  return base$1.initialize.call(this, el, width, height, padding);
};

prototype$O.background = function(bgcolor) {
  if (arguments.length && this._svg) {
    this._svg.style.setProperty('background-color', bgcolor);
  }
  return base$1.background.apply(this, arguments);
};

prototype$O.resize = function(width, height, origin, scaleFactor) {
  base$1.resize.call(this, width, height, origin, scaleFactor);

  if (this._svg) {
    this._svg.setAttribute('width', this._width * this._scale);
    this._svg.setAttribute('height', this._height * this._scale);
    this._svg.setAttribute('viewBox', '0 0 ' + this._width + ' ' + this._height);
    this._root.setAttribute('transform', 'translate(' + this._origin + ')');
  }

  this._dirty = [];

  return this;
};

prototype$O.canvas = function() {
  return this._svg;
};

prototype$O.svg = function() {
  if (!this._svg) return null;

  var attr = {
    class:   'marks',
    width:   this._width * this._scale,
    height:  this._height * this._scale,
    viewBox: '0 0 ' + this._width + ' ' + this._height
  };
  for (var key in metadata) {
    attr[key] = metadata[key];
  }

  var bg = !this._bgcolor ? ''
    : (openTag('rect', {
        width:  this._width,
        height: this._height,
        style:  'fill: ' + this._bgcolor + ';'
      }) + closeTag('rect'));

  return openTag('svg', attr) + bg + this._svg.innerHTML + closeTag('svg');
};


// -- Render entry point --

prototype$O._render = function(scene) {
  // perform spot updates and re-render markup
  if (this._dirtyCheck()) {
    if (this._dirtyAll) this._resetDefs();
    this.draw(this._root, scene);
    domClear(this._root, 1);
  }

  this.updateDefs();

  this._dirty = [];
  ++this._dirtyID;

  return this;
};

// -- Manage SVG definitions ('defs') block --

prototype$O.updateDefs = function() {
  var svg = this._svg,
      defs = this._defs,
      el = defs.el,
      index = 0, id;

  for (id in defs.gradient) {
    if (!el) defs.el = (el = domChild(svg, 0, 'defs', ns));
    index = updateGradient(el, defs.gradient[id], index);
  }

  for (id in defs.clipping) {
    if (!el) defs.el = (el = domChild(svg, 0, 'defs', ns));
    index = updateClipping(el, defs.clipping[id], index);
  }

  // clean-up
  if (el) {
    if (index === 0) {
      svg.removeChild(el);
      defs.el = null;
    } else {
      domClear(el, index);
    }
  }
};

function updateGradient(el, grad, index) {
  var i, n, stop;

  if (grad.gradient === 'radial') {
    // SVG radial gradients automatically transform to normalized bbox
    // coordinates, in a way that is cumbersome to replicate in canvas.
    // So we wrap the radial gradient in a pattern element, allowing us
    // to mantain a circular gradient that matches what canvas provides.
    var pt = domChild(el, index++, 'pattern', ns);
    pt.setAttribute('id', patternPrefix + grad.id);
    pt.setAttribute('viewBox', '0,0,1,1');
    pt.setAttribute('width', '100%');
    pt.setAttribute('height', '100%');
    pt.setAttribute('preserveAspectRatio', 'xMidYMid slice');

    pt = domChild(pt, 0, 'rect', ns);
    pt.setAttribute('width', '1');
    pt.setAttribute('height', '1');
    pt.setAttribute('fill', 'url(' + href() + '#' + grad.id + ')');

    el = domChild(el, index++, 'radialGradient', ns);
    el.setAttribute('id', grad.id);
    el.setAttribute('fx', grad.x1);
    el.setAttribute('fy', grad.y1);
    el.setAttribute('fr', grad.r1);
    el.setAttribute('cx', grad.x2);
    el.setAttribute('cy', grad.y2);
    el.setAttribute( 'r', grad.r2);
  } else {
    el = domChild(el, index++, 'linearGradient', ns);
    el.setAttribute('id', grad.id);
    el.setAttribute('x1', grad.x1);
    el.setAttribute('x2', grad.x2);
    el.setAttribute('y1', grad.y1);
    el.setAttribute('y2', grad.y2);
  }

  for (i=0, n=grad.stops.length; i<n; ++i) {
    stop = domChild(el, i, 'stop', ns);
    stop.setAttribute('offset', grad.stops[i].offset);
    stop.setAttribute('stop-color', grad.stops[i].color);
  }
  domClear(el, i);

  return index;
}

function updateClipping(el, clip, index) {
  var mask;

  el = domChild(el, index, 'clipPath', ns);
  el.setAttribute('id', clip.id);

  if (clip.path) {
    mask = domChild(el, 0, 'path', ns);
    mask.setAttribute('d', clip.path);
  } else {
    mask = domChild(el, 0, 'rect', ns);
    mask.setAttribute('x', 0);
    mask.setAttribute('y', 0);
    mask.setAttribute('width', clip.width);
    mask.setAttribute('height', clip.height);
  }
  domClear(el, 1);

  return index + 1;
}

prototype$O._resetDefs = function() {
  var def = this._defs;
  def.gradient = {};
  def.clipping = {};
};


// -- Manage rendering of items marked as dirty --

prototype$O.dirty = function(item) {
  if (item.dirty !== this._dirtyID) {
    item.dirty = this._dirtyID;
    this._dirty.push(item);
  }
};

prototype$O.isDirty = function(item) {
  return this._dirtyAll
    || !item._svg
    || item.dirty === this._dirtyID;
};

prototype$O._dirtyCheck = function() {
  this._dirtyAll = true;
  var items = this._dirty;
  if (!items.length || !this._dirtyID) return true;

  var id = ++this._dirtyID,
      item, mark, type, mdef, i, n, o;

  for (i=0, n=items.length; i<n; ++i) {
    item = items[i];
    mark = item.mark;

    if (mark.marktype !== type) {
      // memoize mark instance lookup
      type = mark.marktype;
      mdef = Marks[type];
    }

    if (mark.zdirty && mark.dirty !== id) {
      this._dirtyAll = false;
      dirtyParents(item, id);
      mark.items.forEach(function(i) { i.dirty = id; });
    }
    if (mark.zdirty) continue; // handle in standard drawing pass

    if (item.exit) { // EXIT
      if (mdef.nested && mark.items.length) {
        // if nested mark with remaining points, update instead
        o = mark.items[0];
        if (o._svg) this._update(mdef, o._svg, o);
      } else if (item._svg) {
        // otherwise remove from DOM
        o = item._svg.parentNode;
        if (o) o.removeChild(item._svg);
      }
      item._svg = null;
      continue;
    }

    item = (mdef.nested ? mark.items[0] : item);
    if (item._update === id) continue; // already visited

    if (!item._svg || !item._svg.ownerSVGElement) {
      // ENTER
      this._dirtyAll = false;
      dirtyParents(item, id);
    } else {
      // IN-PLACE UPDATE
      this._update(mdef, item._svg, item);
    }
    item._update = id;
  }
  return !this._dirtyAll;
};

function dirtyParents(item, id) {
  for (; item && item.dirty !== id; item=item.mark.group) {
    item.dirty = id;
    if (item.mark && item.mark.dirty !== id) {
      item.mark.dirty = id;
    } else return;
  }
}


// -- Construct & maintain scenegraph to SVG mapping ---

// Draw a mark container.
prototype$O.draw = function(el, scene, prev) {
  if (!this.isDirty(scene)) return scene._svg;

  var renderer = this,
      svg = this._svg,
      mdef = Marks[scene.marktype],
      events = scene.interactive === false ? 'none' : null,
      isGroup = mdef.tag === 'g',
      sibling = null,
      i = 0,
      parent;

  parent = bind(scene, el, prev, 'g', svg);
  parent.setAttribute('class', cssClass(scene));
  if (!isGroup) {
    parent.style.setProperty('pointer-events', events);
  }
  if (scene.clip) {
    parent.setAttribute('clip-path', clip$1(renderer, scene, scene.group));
  } else {
    parent.removeAttribute('clip-path');
  }

  function process(item) {
    var dirty = renderer.isDirty(item),
        node = bind(item, parent, sibling, mdef.tag, svg);

    if (dirty) {
      renderer._update(mdef, node, item);
      if (isGroup) recurse(renderer, node, item);
    }

    sibling = node;
    ++i;
  }

  if (mdef.nested) {
    if (scene.items.length) process(scene.items[0]);
  } else {
    visit(scene, process);
  }

  domClear(parent, i);
  return parent;
};

// Recursively process group contents.
function recurse(renderer, el, group) {
  el = el.lastChild.previousSibling;
  var prev, idx = 0;

  visit(group, function(item) {
    prev = renderer.draw(el, item, prev);
    ++idx;
  });

  // remove any extraneous DOM elements
  domClear(el, 1 + idx);
}

// Bind a scenegraph item to an SVG DOM element.
// Create new SVG elements as needed.
function bind(item, el, sibling, tag, svg) {
  var node = item._svg, doc;

  // create a new dom node if needed
  if (!node) {
    doc = el.ownerDocument;
    node = domCreate(doc, tag, ns);
    item._svg = node;

    if (item.mark) {
      node.__data__ = item;
      node.__values__ = {fill: 'default'};

      // if group, create background, content, and foreground elements
      if (tag === 'g') {
        var bg = domCreate(doc, 'path', ns);
        node.appendChild(bg);
        bg.__data__ = item;

        var cg = domCreate(doc, 'g', ns);
        node.appendChild(cg);
        cg.__data__ = item;

        var fg = domCreate(doc, 'path', ns);
        node.appendChild(fg);
        fg.__data__ = item;
        fg.__values__ = {fill: 'default'};
      }
    }
  }

  // (re-)insert if (a) not contained in SVG or (b) sibling order has changed
  if (node.ownerSVGElement !== svg || siblingCheck(node, sibling)) {
    el.insertBefore(node, sibling ? sibling.nextSibling : el.firstChild);
  }

  return node;
}

function siblingCheck(node, sibling) {
  return node.parentNode
    && node.parentNode.childNodes.length > 1
    && node.previousSibling != sibling; // treat null/undefined the same
}


// -- Set attributes & styles on SVG elements ---

var element = null, // temp var for current SVG element
    values = null;  // temp var for current values hash

// Extra configuration for certain mark types
var mark_extras = {
  group: function(mdef, el, item) {
    var fg, bg;

    element = fg = el.childNodes[2];
    values = fg.__values__;
    mdef.foreground(emit, item, this);

    values = el.__values__; // use parent's values hash
    element = el.childNodes[1];
    mdef.content(emit, item, this);

    element = bg = el.childNodes[0];
    mdef.background(emit, item, this);

    var value = item.mark.interactive === false ? 'none' : null;
    if (value !== values.events) {
      fg.style.setProperty('pointer-events', value);
      bg.style.setProperty('pointer-events', value);
      values.events = value;
    }

    if (item.strokeForeground && item.stroke) {
      const fill = item.fill;
      fg.style.removeProperty('display');

      // set style of background
      this.style(bg, item);
      bg.style.removeProperty('stroke');

      // set style of foreground
      if (fill) item.fill = null;
      values = fg.__values__;
      this.style(fg, item);
      if (fill) item.fill = fill;

      // leave element null to prevent downstream styling
      element = null;
    } else {
      // ensure foreground is ignored
      fg.style.setProperty('display', 'none');
      fg.style.setProperty('fill', 'none');
    }
  },
  image: function(mdef, el, item) {
    if (item.smooth === false) {
      setStyle(el, 'image-rendering', 'optimizeSpeed');
      setStyle(el, 'image-rendering', 'pixelated');
    } else {
      setStyle(el, 'image-rendering', null);
    }
  },
  text: function(mdef, el, item) {
    var tl = textLines(item),
        key, value, doc, lh;

    if (isArray(tl)) {
      // multi-line text
      value = tl.map(_ => textValue(item, _));
      key = value.join('\n'); // content cache key

      if (key !== values.text) {
        domClear(el, 0);
        doc = el.ownerDocument;
        lh = lineHeight(item);
        value.forEach((t, i) => {
          const ts = domCreate(doc, 'tspan', ns);
          ts.__data__ = item; // data binding
          ts.textContent = t;
          if (i) {
            ts.setAttribute('x', 0);
            ts.setAttribute('dy', lh);
          }
          el.appendChild(ts);
        });
        values.text = key;
      }
    } else {
      // single-line text
      value = textValue(item, tl);
      if (value !== values.text) {
        el.textContent = value;
        values.text = value;
      }
    }

    setStyle(el, 'font-family', fontFamily(item));
    setStyle(el, 'font-size', fontSize(item) + 'px');
    setStyle(el, 'font-style', item.fontStyle);
    setStyle(el, 'font-variant', item.fontVariant);
    setStyle(el, 'font-weight', item.fontWeight);
  }
};

function setStyle(el, name, value) {
  if (value !== values[name]) {
    if (value == null) {
      el.style.removeProperty(name);
    } else {
      el.style.setProperty(name, value + '');
    }
    values[name] = value;
  }
}

prototype$O._update = function(mdef, el, item) {
  // set dom element and values cache
  // provides access to emit method
  element = el;
  values = el.__values__;

  // apply svg attributes
  mdef.attr(emit, item, this);

  // some marks need special treatment
  var extra = mark_extras[mdef.type];
  if (extra) extra.call(this, mdef, el, item);

  // apply svg css styles
  // note: element may be modified by 'extra' method
  if (element) this.style(element, item);
};

function emit(name, value, ns) {
  // early exit if value is unchanged
  if (value === values[name]) return;

  if (value != null) {
    // if value is provided, update DOM attribute
    if (ns) {
      element.setAttributeNS(ns, name, value);
    } else {
      element.setAttribute(name, value);
    }
  } else {
    // else remove DOM attribute
    if (ns) {
      element.removeAttributeNS(ns, name);
    } else {
      element.removeAttribute(name);
    }
  }

  // note current value for future comparison
  values[name] = value;
}

prototype$O.style = function(el, o) {
  if (o == null) return;
  var i, n, prop, name, value;

  for (i=0, n=styleProperties.length; i<n; ++i) {
    prop = styleProperties[i];
    value = o[prop];

    if (prop === 'font') {
      value = fontFamily(o);
    }

    if (value === values[prop]) continue;

    name = styles[prop];
    if (value == null) {
      if (name === 'fill') {
        el.style.setProperty(name, 'none');
      } else {
        el.style.removeProperty(name);
      }
    } else {
      if (isGradient(value)) {
        value = gradientRef(value, this._defs.gradient, href());
      }
      el.style.setProperty(name, value + '');
    }

    values[prop] = value;
  }
};

function href() {
  var loc;
  return typeof window === 'undefined' ? ''
    : (loc = window.location).hash ? loc.href.slice(0, -loc.hash.length)
    : loc.href;
}

function SVGStringRenderer(loader) {
  Renderer.call(this, loader);

  this._text = {
    head: '',
    bg:   '',
    root: '',
    foot: '',
    defs: '',
    body: ''
  };

  this._defs = {
    gradient: {},
    clipping: {}
  };
}

var prototype$P = inherits(SVGStringRenderer, Renderer);
var base$2 = Renderer.prototype;

prototype$P.resize = function(width, height, origin, scaleFactor) {
  base$2.resize.call(this, width, height, origin, scaleFactor);
  var o = this._origin,
      t = this._text;

  var attr = {
    class:   'marks',
    width:   this._width * this._scale,
    height:  this._height * this._scale,
    viewBox: '0 0 ' + this._width + ' ' + this._height
  };
  for (var key in metadata) {
    attr[key] = metadata[key];
  }

  t.head = openTag('svg', attr);

  var bg = this._bgcolor;
  if (bg === 'transparent' || bg === 'none') bg = null;

  if (bg) {
    t.bg = openTag('rect', {
      width:  this._width,
      height: this._height,
      style:  'fill: ' + bg + ';'
    }) + closeTag('rect');
  } else {
    t.bg = '';
  }

  t.root = openTag('g', {
    transform: 'translate(' + o + ')'
  });

  t.foot = closeTag('g') + closeTag('svg');

  return this;
};

prototype$P.background = function() {
  var rv = base$2.background.apply(this, arguments);
  if (arguments.length && this._text.head) {
    this.resize(this._width, this._height, this._origin, this._scale);
  }
  return rv;
};

prototype$P.svg = function() {
  var t = this._text;
  return t.head + t.bg + t.defs + t.root + t.body + t.foot;
};

prototype$P._render = function(scene) {
  this._text.body = this.mark(scene);
  this._text.defs = this.buildDefs();
  return this;
};

prototype$P.buildDefs = function() {
  var all = this._defs,
      defs = '',
      i, id, def, tag, stops;

  for (id in all.gradient) {
    def = all.gradient[id];
    stops = def.stops;

    if (def.gradient === 'radial') {
      // SVG radial gradients automatically transform to normalized bbox
      // coordinates, in a way that is cumbersome to replicate in canvas.
      // So we wrap the radial gradient in a pattern element, allowing us
      // to mantain a circular gradient that matches what canvas provides.

      defs += openTag(tag = 'pattern', {
        id: patternPrefix + id,
        viewBox: '0,0,1,1',
        width: '100%',
        height: '100%',
        preserveAspectRatio: 'xMidYMid slice'
      });

      defs += openTag('rect', {
        width: '1',
        height: '1',
        fill: 'url(#' + id + ')'
      }) + closeTag('rect');

      defs += closeTag(tag);

      defs += openTag(tag = 'radialGradient', {
        id: id,
        fx: def.x1,
        fy: def.y1,
        fr: def.r1,
        cx: def.x2,
        cy: def.y2,
         r: def.r2
      });
    } else {
      defs += openTag(tag = 'linearGradient', {
        id: id,
        x1: def.x1,
        x2: def.x2,
        y1: def.y1,
        y2: def.y2
      });
    }

    for (i=0; i<stops.length; ++i) {
      defs += openTag('stop', {
        offset: stops[i].offset,
        'stop-color': stops[i].color
      }) + closeTag('stop');
    }

    defs += closeTag(tag);
  }

  for (id in all.clipping) {
    def = all.clipping[id];

    defs += openTag('clipPath', {id: id});

    if (def.path) {
      defs += openTag('path', {
        d: def.path
      }) + closeTag('path');
    } else {
      defs += openTag('rect', {
        x: 0,
        y: 0,
        width: def.width,
        height: def.height
      }) + closeTag('rect');
    }

    defs += closeTag('clipPath');
  }

  return (defs.length > 0) ? openTag('defs') + defs + closeTag('defs') : '';
};

var object;

function emit$1(name, value, ns, prefixed) {
  object[prefixed || name] = value;
}

prototype$P.attributes = function(attr, item) {
  object = {};
  attr(emit$1, item, this);
  return object;
};

prototype$P.href = function(item) {
  var that = this,
      href = item.href,
      attr;

  if (href) {
    if (attr = that._hrefs && that._hrefs[href]) {
      return attr;
    } else {
      that.sanitizeURL(href).then(function(attr) {
        // rewrite to use xlink namespace
        // note that this will be deprecated in SVG 2.0
        attr['xlink:href'] = attr.href;
        attr.href = null;
        (that._hrefs || (that._hrefs = {}))[href] = attr;
      });
    }
  }
  return null;
};

prototype$P.mark = function(scene) {
  var renderer = this,
      mdef = Marks[scene.marktype],
      tag  = mdef.tag,
      defs = this._defs,
      str = '',
      style;

  if (tag !== 'g' && scene.interactive === false) {
    style = 'style="pointer-events: none;"';
  }

  // render opening group tag
  str += openTag('g', {
    'class': cssClass(scene),
    'clip-path': scene.clip ? clip$1(renderer, scene, scene.group) : null
  }, style);

  // render contained elements
  function process(item) {
    var href = renderer.href(item);
    if (href) str += openTag('a', href);

    style = (tag !== 'g') ? applyStyles(item, scene, tag, defs) : null;
    str += openTag(tag, renderer.attributes(mdef.attr, item), style);

    if (tag === 'text') {
      const tl = textLines(item);
      if (isArray(tl)) {
        // multi-line text
        const attrs = {x: 0, dy: lineHeight(item)};
        for (let i=0; i<tl.length; ++i) {
          str += openTag('tspan', i ? attrs: null)
            + escape_text(textValue(item, tl[i]))
            + closeTag('tspan');
        }
      } else {
        // single-line text
        str += escape_text(textValue(item, tl));
      }
    } else if (tag === 'g') {
      const fore = item.strokeForeground,
            fill = item.fill,
            stroke = item.stroke;

      if (fore && stroke) {
        item.stroke = null;
      }

      str += openTag('path', renderer.attributes(mdef.background, item),
        applyStyles(item, scene, 'bgrect', defs)) + closeTag('path');

      str += openTag('g', renderer.attributes(mdef.content, item))
        + renderer.markGroup(item)
        + closeTag('g');

      if (fore && stroke) {
        if (fill) item.fill = null;
        item.stroke = stroke;

        str += openTag('path', renderer.attributes(mdef.foreground, item),
          applyStyles(item, scene, 'bgrect', defs)) + closeTag('path');

        if (fill) item.fill = fill;
      } else {
        str += openTag('path', renderer.attributes(mdef.foreground, item),
          applyStyles({}, scene, 'bgfore', defs)) + closeTag('path');
      }
    }

    str += closeTag(tag);
    if (href) str += closeTag('a');
  }

  if (mdef.nested) {
    if (scene.items && scene.items.length) process(scene.items[0]);
  } else {
    visit(scene, process);
  }

  // render closing group tag
  return str + closeTag('g');
};

prototype$P.markGroup = function(scene) {
  var renderer = this,
      str = '';

  visit(scene, function(item) {
    str += renderer.mark(item);
  });

  return str;
};

function applyStyles(o, mark, tag, defs) {
  if (o == null) return '';
  var i, n, prop, name, value, s = '';

  if (tag === 'bgrect' && mark.interactive === false) {
    s += 'pointer-events: none; ';
  }

  if (tag === 'bgfore') {
    if (mark.interactive === false) {
      s += 'pointer-events: none; ';
    }
    s += 'display: none; ';
  }

  if (tag === 'image') {
    if (o.smooth === false) {
      s += 'image-rendering: optimizeSpeed; image-rendering: pixelated; ';
    }
  }

  if (tag === 'text') {
    s += 'font-family: ' + fontFamily(o) + '; ';
    s += 'font-size: ' + fontSize(o) + 'px; ';
    if (o.fontStyle) s += 'font-style: ' + o.fontStyle + '; ';
    if (o.fontVariant) s += 'font-variant: ' + o.fontVariant + '; ';
    if (o.fontWeight) s += 'font-weight: ' + o.fontWeight + '; ';
  }

  for (i=0, n=styleProperties.length; i<n; ++i) {
    prop = styleProperties[i];
    name = styles[prop];
    value = o[prop];

    if (value == null) {
      if (name === 'fill') {
        s += 'fill: none; ';
      }
    } else if (value === 'transparent' && (name === 'fill' || name === 'stroke')) {
      // transparent is not a legal SVG value, so map to none instead
      s += name + ': none; ';
    } else {
      if (isGradient(value)) {
        value = gradientRef(value, defs.gradient, '');
      }
      s += name + ': ' + value + '; ';
    }
  }

  return s ? 'style="' + s.trim() + '"' : null;
}

function escape_text(s) {
  return s.replace(/&/g, '&amp;')
          .replace(/</g, '&lt;')
          .replace(/>/g, '&gt;');
}

var Canvas = 'canvas';
var PNG = 'png';
var SVG = 'svg';
var None$2 = 'none';

var RenderType = {
  Canvas: Canvas,
  PNG:    PNG,
  SVG:    SVG,
  None:   None$2
};

var modules = {};

modules[Canvas] = modules[PNG] = {
  renderer: CanvasRenderer,
  headless: CanvasRenderer,
  handler:  CanvasHandler
};

modules[SVG] = {
  renderer: SVGRenderer,
  headless: SVGStringRenderer,
  handler:  SVGHandler
};

modules[None$2] = {};

function renderModule(name, _) {
  name = String(name || '').toLowerCase();
  if (arguments.length > 1) {
    modules[name] = _;
    return this;
  } else {
    return modules[name];
  }
}

function intersect(scene, bounds, filter) {
  const hits = [], // intersection results
        box = new Bounds().union(bounds), // defensive copy
        type = scene.marktype;

  return type ? intersectMark(scene, box, filter, hits)
    : type === 'group' ? intersectGroup(scene, box, filter, hits)
    : error('Intersect scene must be mark node or group item.');
}

function intersectMark(mark, box, filter, hits) {
  if (visitMark(mark, box, filter)) {
    const items = mark.items,
          type = mark.marktype,
          n = items.length;

    let i = 0;

    if (type === 'group') {
      for (; i<n; ++i) {
        intersectGroup(items[i], box, filter, hits);
      }
    } else {
      for (const test = Marks[type].isect; i<n; ++i) {
        let item = items[i];
        if (intersectItem(item, box, test)) hits.push(item);
      }
    }
  }
  return hits;
}

function visitMark(mark, box, filter) {
  // process if bounds intersect and if
  // (1) mark is a group mark (so we must recurse), or
  // (2) mark is interactive and passes filter
  return mark.bounds && box.intersects(mark.bounds) && (
    mark.marktype === 'group' ||
    mark.interactive !== false && (!filter || filter(mark))
  );
}

function intersectGroup(group, box, filter, hits) {
  // test intersect against group
  // skip groups by default unless filter says otherwise
  if ((filter && filter(group.mark)) &&
      intersectItem(group, box, Marks.group.isect)) {
    hits.push(group);
  }

  // recursively test children marks
  // translate box to group coordinate space
  const marks = group.items,
        n = marks && marks.length;

  if (n) {
    const x = group.x || 0,
          y = group.y || 0;
    box.translate(-x, -y);
    for (let i=0; i<n; ++i) {
      intersectMark(marks[i], box, filter, hits);
    }
    box.translate(x, y);
  }

  return hits;
}

function intersectItem(item, box, test) {
  // test bounds enclosure, bounds intersection, then detailed test
  const bounds = item.bounds;
  return box.encloses(bounds) || (box.intersects(bounds) && test(item, box));
}

var clipBounds = new Bounds();

function boundClip(mark) {
  var clip = mark.clip;

  if (isFunction(clip)) {
    clip(context(clipBounds.clear()));
  } else if (clip) {
    clipBounds.set(0, 0, mark.group.width, mark.group.height);
  } else return;

  mark.bounds.intersect(clipBounds);
}

var TOLERANCE = 1e-9;

function sceneEqual(a, b, key) {
  return (a === b) ? true
    : (key === 'path') ? pathEqual(a, b)
    : (a instanceof Date && b instanceof Date) ? +a === +b
    : (isNumber(a) && isNumber(b)) ? Math.abs(a - b) <= TOLERANCE
    : (!a || !b || !isObject(a) && !isObject(b)) ? a == b
    : (a == null || b == null) ? false
    : objectEqual(a, b);
}

function pathEqual(a, b) {
  return sceneEqual(pathParse(a), pathParse(b));
}

function objectEqual(a, b) {
  var ka = Object.keys(a),
      kb = Object.keys(b),
      key, i;

  if (ka.length !== kb.length) return false;

  ka.sort();
  kb.sort();

  for (i = ka.length - 1; i >= 0; i--) {
    if (ka[i] != kb[i]) return false;
  }

  for (i = ka.length - 1; i >= 0; i--) {
    key = ka[i];
    if (!sceneEqual(a[key], b[key], key)) return false;
  }

  return typeof a === typeof b;
}

/**
 * Calculate bounding boxes for scenegraph items.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {object} params.mark - The scenegraph mark instance to bound.
 */
function Bound(params) {
  Transform.call(this, null, params);
}

var prototype$Q = inherits(Bound, Transform);

prototype$Q.transform = function(_, pulse) {
  var view = pulse.dataflow,
      mark = _.mark,
      type = mark.marktype,
      entry = Marks[type],
      bound = entry.bound,
      markBounds = mark.bounds, rebound;

  if (entry.nested) {
    // multi-item marks have a single bounds instance
    if (mark.items.length) view.dirty(mark.items[0]);
    markBounds = boundItem$1(mark, bound);
    mark.items.forEach(function(item) {
      item.bounds.clear().union(markBounds);
    });
  }

  else if (type === Group || _.modified()) {
    // operator parameters modified -> re-bound all items
    // updates group bounds in response to modified group content
    pulse.visit(pulse.MOD, function(item) { view.dirty(item); });
    markBounds.clear();
    mark.items.forEach(function(item) {
      markBounds.union(boundItem$1(item, bound));
    });

    // force reflow for axes/legends/titles to propagate any layout changes
    switch (mark.role) {
      case AxisRole:
      case LegendRole:
      case TitleRole:
        pulse.reflow();
    }
  }

  else {
    // incrementally update bounds, re-bound mark as needed
    rebound = pulse.changed(pulse.REM);

    pulse.visit(pulse.ADD, function(item) {
      markBounds.union(boundItem$1(item, bound));
    });

    pulse.visit(pulse.MOD, function(item) {
      rebound = rebound || markBounds.alignsWith(item.bounds);
      view.dirty(item);
      markBounds.union(boundItem$1(item, bound));
    });

    if (rebound) {
      markBounds.clear();
      mark.items.forEach(function(item) { markBounds.union(item.bounds); });
    }
  }

  // ensure mark bounds do not exceed any clipping region
  boundClip(mark);

  return pulse.modifies('bounds');
};

function boundItem$1(item, bound, opt) {
  return bound(item.bounds.clear(), item, opt);
}

var COUNTER_NAME = ':vega_identifier:';

/**
 * Adds a unique identifier to all added tuples.
 * This transform creates a new signal that serves as an id counter.
 * As a result, the id counter is shared across all instances of this
 * transform, generating unique ids across multiple data streams. In
 * addition, this signal value can be included in a snapshot of the
 * dataflow state, enabling correct resumption of id allocation.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {string} params.as - The field name for the generated identifier.
 */
function Identifier(params) {
  Transform.call(this, 0, params);
}

Identifier.Definition = {
  "type": "Identifier",
  "metadata": {"modifies": true},
  "params": [
    { "name": "as", "type": "string", "required": true }
  ]
};

var prototype$R = inherits(Identifier, Transform);

prototype$R.transform = function(_, pulse) {
  var counter = getCounter(pulse.dataflow),
      id = counter.value,
      as = _.as;

  pulse.visit(pulse.ADD, function(t) {
    if (!t[as]) t[as] = ++id;
  });

  counter.set(this.value = id);
  return pulse;
};

function getCounter(view) {
  var counter = view._signals[COUNTER_NAME];
  if (!counter) {
    view._signals[COUNTER_NAME] = (counter = view.add(0));
  }
  return counter;
}

/**
 * Bind scenegraph items to a scenegraph mark instance.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {object} params.markdef - The mark definition for creating the mark.
 *   This is an object of legal scenegraph mark properties which *must* include
 *   the 'marktype' property.
 */
function Mark(params) {
  Transform.call(this, null, params);
}

var prototype$S = inherits(Mark, Transform);

prototype$S.transform = function(_, pulse) {
  var mark = this.value;

  // acquire mark on first invocation, bind context and group
  if (!mark) {
    mark = pulse.dataflow.scenegraph().mark(_.markdef, lookup$1(_), _.index);
    mark.group.context = _.context;
    if (!_.context.group) _.context.group = mark.group;
    mark.source = this.source; // point to upstream collector
    mark.clip = _.clip;
    mark.interactive = _.interactive;
    this.value = mark;
  }

  // initialize entering items
  var Init = mark.marktype === Group ? GroupItem : Item;
  pulse.visit(pulse.ADD, function(item) { Init.call(item, mark); });

  // update clipping and/or interactive status
  if (_.modified('clip') || _.modified('interactive')) {
    mark.clip = _.clip;
    mark.interactive = !!_.interactive;
    mark.zdirty = true; // force scenegraph re-eval
    pulse.reflow();
  }

  // bind items array to scenegraph mark
  mark.items = pulse.source;
  return pulse;
};

function lookup$1(_) {
  var g = _.groups, p = _.parent;
  return g && g.size === 1 ? g.get(Object.keys(g.object)[0])
    : g && p ? g.lookup(p)
    : null;
}

/**
 * Analyze items for overlap, changing opacity to hide items with
 * overlapping bounding boxes. This transform will preserve at least
 * two items (e.g., first and last) even if overlap persists.
 * @param {object} params - The parameters for this operator.
 * @param {function(*,*): number} [params.sort] - A comparator
 *   function for sorting items.
 * @param {object} [params.method] - The overlap removal method to apply.
 *   One of 'parity' (default, hide every other item until there is no
 *   more overlap) or 'greedy' (sequentially scan and hide and items that
 *   overlap with the last visible item).
 * @param {object} [params.boundScale] - A scale whose range should be used
 *   to bound the items. Items exceeding the bounds of the scale range
 *   will be treated as overlapping. If null or undefined, no bounds check
 *   will be applied.
 * @param {object} [params.boundOrient] - The orientation of the scale
 *   (top, bottom, left, or right) used to bound items. This parameter is
 *   ignored if boundScale is null or undefined.
 * @param {object} [params.boundTolerance] - The tolerance in pixels for
 *   bound inclusion testing (default 1). This specifies by how many pixels
 *   an item's bounds may exceed the scale range bounds and not be culled.
 * @constructor
 */
function Overlap(params) {
  Transform.call(this, null, params);
}

var prototype$T = inherits(Overlap, Transform);

var methods = {
  parity: function(items) {
    return items.filter((item, i) => i % 2 ? (item.opacity = 0) : 1);
  },
  greedy: function(items, sep) {
    var a;
    return items.filter((b, i) => {
      if (!i || !intersect$1(a.bounds, b.bounds, sep)) {
        a = b;
        return 1;
      } else {
        return b.opacity = 0;
      }
    });
  }
};

// compute bounding box intersection
// including padding pixels of separation
function intersect$1(a, b, sep) {
  return sep > Math.max(
    b.x1 - a.x2,
    a.x1 - b.x2,
    b.y1 - a.y2,
    a.y1 - b.y2
  );
}

function hasOverlap(items, pad) {
  for (var i=1, n=items.length, a=items[0].bounds, b; i<n; a=b, ++i) {
    if (intersect$1(a, b = items[i].bounds, pad)) return true;
  }
}

function hasBounds(item) {
  var b = item.bounds;
  return b.width() > 1 && b.height() > 1;
}

function boundTest(scale, orient, tolerance) {
  var range = scale.range(),
      b = new Bounds();

  if (orient === Top || orient === Bottom) {
    b.set(range[0], -Infinity, range[1], +Infinity);
  } else {
    b.set(-Infinity, range[0], +Infinity, range[1]);
  }
  b.expand(tolerance || 1);

  return item => b.encloses(item.bounds);
}

// reset all items to be fully opaque
function reset(source) {
  source.forEach(item => item.opacity = 1);
  return source;
}

// add all tuples to mod, fork pulse if parameters were modified
// fork prevents cross-stream tuple pollution (e.g., pulse from scale)
function reflow(pulse, _) {
  return pulse.reflow(_.modified()).modifies('opacity');
}

prototype$T.transform = function(_, pulse) {
  var reduce = methods[_.method] || methods.parity,
      source = pulse.materialize(pulse.SOURCE).source,
      sep = _.separation || 0,
      items, test, bounds;

  if (!source || !source.length) return;

  if (!_.method) {
    // early exit if method is falsy
    if (_.modified('method')) {
      reset(source);
      pulse = reflow(pulse, _);
    }
    return pulse;
  }

  if (_.sort) {
    source = source.slice().sort(_.sort);
  }

  // skip labels with no content
  source = source.filter(hasBounds);

  items = reset(source);
  pulse = reflow(pulse, _);

  if (items.length >= 3 && hasOverlap(items, sep)) {
    do {
      items = reduce(items, sep);
    } while (items.length >= 3 && hasOverlap(items, sep));

    if (items.length < 3 && !peek(source).opacity) {
      if (items.length > 1) peek(items).opacity = 0;
      peek(source).opacity = 1;
    }
  }

  if (_.boundScale && _.boundTolerance >= 0) {
    test = boundTest(_.boundScale, _.boundOrient, +_.boundTolerance);
    source.forEach(item => {
      if (!test(item)) item.opacity = 0;
    });
  }

  // re-calculate mark bounds
  bounds = items[0].mark.bounds.clear();
  source.forEach(item => {
    if (item.opacity) bounds.union(item.bounds);
  });

  return pulse;
};

/**
 * Queue modified scenegraph items for rendering.
 * @constructor
 */
function Render(params) {
  Transform.call(this, null, params);
}

var prototype$U = inherits(Render, Transform);

prototype$U.transform = function(_, pulse) {
  var view = pulse.dataflow;

  pulse.visit(pulse.ALL, function(item) { view.dirty(item); });

  // set z-index dirty flag as needed
  if (pulse.fields && pulse.fields['zindex']) {
    var item = pulse.source && pulse.source[0];
    if (item) item.mark.zdirty = true;
  }
};

const tempBounds$2 = new Bounds();

function set(item, property, value) {
  return item[property] === value ? 0
    : (item[property] = value, 1);
}

function isYAxis(mark) {
  var orient = mark.items[0].datum.orient;
  return orient === Left || orient === Right;
}

function axisIndices(datum) {
  var index = +datum.grid;
  return [
    datum.ticks  ? index++ : -1, // ticks index
    datum.labels ? index++ : -1, // labels index
    index + (+datum.domain)      // title index
  ];
}

function axisLayout(view, axis, width, height) {
  var item = axis.items[0],
      datum = item.datum,
      orient = datum.orient,
      delta = datum.translate != null ? datum.translate : 0.5,
      indices = axisIndices(datum),
      range = item.range,
      offset = item.offset,
      position = item.position,
      minExtent = item.minExtent,
      maxExtent = item.maxExtent,
      title = datum.title && item.items[indices[2]].items[0],
      titlePadding = item.titlePadding,
      bounds = item.bounds,
      dl = title && multiLineOffset(title),
      x = 0, y = 0, i, s;

  tempBounds$2.clear().union(bounds);
  bounds.clear();
  if ((i=indices[0]) > -1) bounds.union(item.items[i].bounds);
  if ((i=indices[1]) > -1) bounds.union(item.items[i].bounds);

  // position axis group and title
  switch (orient) {
    case Top:
      x = position || 0;
      y = -offset;
      s = Math.max(minExtent, Math.min(maxExtent, -bounds.y1));
      if (title) s = axisTitleLayout(view, title, s, titlePadding, dl, 0, -1, bounds);
      bounds.add(0, -s).add(range, 0);
      break;
    case Left:
      x = -offset;
      y = position || 0;
      s = Math.max(minExtent, Math.min(maxExtent, -bounds.x1));
      if (title) s = axisTitleLayout(view, title, s, titlePadding, dl, 1, -1, bounds);
      bounds.add(-s, 0).add(0, range);
      break;
    case Right:
      x = width + offset;
      y = position || 0;
      s = Math.max(minExtent, Math.min(maxExtent, bounds.x2));
      if (title) s = axisTitleLayout(view, title, s, titlePadding, dl, 1, 1, bounds);
      bounds.add(0, 0).add(s, range);
      break;
    case Bottom:
      x = position || 0;
      y = height + offset;
      s = Math.max(minExtent, Math.min(maxExtent, bounds.y2));
      if (title) s = axisTitleLayout(view, title, s, titlePadding, 0, 0, 1, bounds);
      bounds.add(0, 0).add(range, s);
      break;
    default:
      x = item.x;
      y = item.y;
  }

  // update bounds
  boundStroke(bounds.translate(x, y), item);

  if (set(item, 'x', x + delta) | set(item, 'y', y + delta)) {
    item.bounds = tempBounds$2;
    view.dirty(item);
    item.bounds = bounds;
    view.dirty(item);
  }

  return item.mark.bounds.clear().union(bounds);
}

function axisTitleLayout(view, title, offset, pad, dl, isYAxis, sign, bounds) {
  var b = title.bounds, dx = 0, dy = 0;

  if (title.auto) {
    view.dirty(title);

    offset += pad;

    isYAxis
      ? dx = (title.x || 0) - (title.x = sign * (offset + dl))
      : dy = (title.y || 0) - (title.y = sign * (offset + dl));

    title.mark.bounds.clear().union(b.translate(-dx, -dy));
    view.dirty(title);

    if (isYAxis) {
      bounds.add(0, b.y1).add(0, b.y2);
      offset += b.width();
    } else {
      bounds.add(b.x1, 0).add(b.x2, 0);
      offset += b.height();
    }
  } else {
    bounds.union(b);
  }

  return offset;
}

function gridLayoutGroups(group) {
  var groups = group.items,
      n = groups.length,
      i = 0, mark, items;

  var views = {
    marks:      [],
    rowheaders: [],
    rowfooters: [],
    colheaders: [],
    colfooters: [],
    rowtitle: null,
    coltitle: null
  };

  // layout axes, gather legends, collect bounds
  for (; i<n; ++i) {
    mark = groups[i];
    items = mark.items;
    if (mark.marktype === Group) {
      switch (mark.role) {
        case AxisRole:
        case LegendRole:
        case TitleRole:
          break;
        case RowHeader: views.rowheaders.push(...items); break;
        case RowFooter: views.rowfooters.push(...items); break;
        case ColHeader: views.colheaders.push(...items); break;
        case ColFooter: views.colfooters.push(...items); break;
        case RowTitle:  views.rowtitle = items[0]; break;
        case ColTitle:  views.coltitle = items[0]; break;
        default:        views.marks.push(...items);
      }
    }
  }

  return views;
}

function bboxFlush(item) {
  return new Bounds().set(0, 0, item.width || 0, item.height || 0);
}

function bboxFull(item) {
  var b = item.bounds.clone();
  return b.empty()
    ? b.set(0, 0, 0, 0)
    : b.translate(-(item.x || 0), -(item.y || 0));
}

function get$2(opt, key, d) {
  var v = isObject(opt) ? opt[key] : opt;
  return v != null ? v : (d !== undefined ? d : 0);
}

function offsetValue(v) {
  return v < 0 ? Math.ceil(-v) : 0;
}

function gridLayout(view, groups, opt) {
  var dirty = !opt.nodirty,
      bbox = opt.bounds === Flush ? bboxFlush : bboxFull,
      bounds = tempBounds$2.set(0, 0, 0, 0),
      alignCol = get$2(opt.align, Column),
      alignRow = get$2(opt.align, Row),
      padCol = get$2(opt.padding, Column),
      padRow = get$2(opt.padding, Row),
      ncols = opt.columns || groups.length,
      nrows = ncols < 0 ? 1 : Math.ceil(groups.length / ncols),
      n = groups.length,
      xOffset = Array(n), xExtent = Array(ncols), xMax = 0,
      yOffset = Array(n), yExtent = Array(nrows), yMax = 0,
      dx = Array(n), dy = Array(n), boxes = Array(n),
      m, i, c, r, b, g, px, py, x, y, offset;

  for (i=0; i<ncols; ++i) xExtent[i] = 0;
  for (i=0; i<nrows; ++i) yExtent[i] = 0;

  // determine offsets for each group
  for (i=0; i<n; ++i) {
    g = groups[i];
    b = boxes[i] = bbox(g);
    g.x = g.x || 0; dx[i] = 0;
    g.y = g.y || 0; dy[i] = 0;
    c = i % ncols;
    r = ~~(i / ncols);
    xMax = Math.max(xMax, px = Math.ceil(b.x2));
    yMax = Math.max(yMax, py = Math.ceil(b.y2));
    xExtent[c] = Math.max(xExtent[c], px);
    yExtent[r] = Math.max(yExtent[r], py);
    xOffset[i] = padCol + offsetValue(b.x1);
    yOffset[i] = padRow + offsetValue(b.y1);
    if (dirty) view.dirty(groups[i]);
  }

  // set initial alignment offsets
  for (i=0; i<n; ++i) {
    if (i % ncols === 0) xOffset[i] = 0;
    if (i < ncols) yOffset[i] = 0;
  }

  // enforce column alignment constraints
  if (alignCol === Each) {
    for (c=1; c<ncols; ++c) {
      for (offset=0, i=c; i<n; i += ncols) {
        if (offset < xOffset[i]) offset = xOffset[i];
      }
      for (i=c; i<n; i += ncols) {
        xOffset[i] = offset + xExtent[c-1];
      }
    }
  } else if (alignCol === All) {
    for (offset=0, i=0; i<n; ++i) {
      if (i % ncols && offset < xOffset[i]) offset = xOffset[i];
    }
    for (i=0; i<n; ++i) {
      if (i % ncols) xOffset[i] = offset + xMax;
    }
  } else {
    for (alignCol=false, c=1; c<ncols; ++c) {
      for (i=c; i<n; i += ncols) {
        xOffset[i] += xExtent[c-1];
      }
    }
  }

  // enforce row alignment constraints
  if (alignRow === Each) {
    for (r=1; r<nrows; ++r) {
      for (offset=0, i=r*ncols, m=i+ncols; i<m; ++i) {
        if (offset < yOffset[i]) offset = yOffset[i];
      }
      for (i=r*ncols; i<m; ++i) {
        yOffset[i] = offset + yExtent[r-1];
      }
    }
  } else if (alignRow === All) {
    for (offset=0, i=ncols; i<n; ++i) {
      if (offset < yOffset[i]) offset = yOffset[i];
    }
    for (i=ncols; i<n; ++i) {
      yOffset[i] = offset + yMax;
    }
  } else {
    for (alignRow=false, r=1; r<nrows; ++r) {
      for (i=r*ncols, m=i+ncols; i<m; ++i) {
        yOffset[i] += yExtent[r-1];
      }
    }
  }

  // perform horizontal grid layout
  for (x=0, i=0; i<n; ++i) {
    x = xOffset[i] + (i % ncols ? x : 0);
    dx[i] += x - groups[i].x;
  }

  // perform vertical grid layout
  for (c=0; c<ncols; ++c) {
    for (y=0, i=c; i<n; i += ncols) {
      y += yOffset[i];
      dy[i] += y - groups[i].y;
    }
  }

  // perform horizontal centering
  if (alignCol && get$2(opt.center, Column) && nrows > 1) {
    for (i=0; i<n; ++i) {
      b = alignCol === All ? xMax : xExtent[i % ncols];
      x = b - boxes[i].x2 - groups[i].x - dx[i];
      if (x > 0) dx[i] += x / 2;
    }
  }

  // perform vertical centering
  if (alignRow && get$2(opt.center, Row) && ncols !== 1) {
    for (i=0; i<n; ++i) {
      b = alignRow === All ? yMax : yExtent[~~(i / ncols)];
      y = b - boxes[i].y2 - groups[i].y - dy[i];
      if (y > 0) dy[i] += y / 2;
    }
  }

  // position grid relative to anchor
  for (i=0; i<n; ++i) {
    bounds.union(boxes[i].translate(dx[i], dy[i]));
  }
  x = get$2(opt.anchor, X);
  y = get$2(opt.anchor, Y);
  switch (get$2(opt.anchor, Column)) {
    case End:    x -= bounds.width(); break;
    case Middle: x -= bounds.width() / 2;
  }
  switch (get$2(opt.anchor, Row)) {
    case End:    y -= bounds.height(); break;
    case Middle: y -= bounds.height() / 2;
  }
  x = Math.round(x);
  y = Math.round(y);

  // update mark positions, bounds, dirty
  bounds.clear();
  for (i=0; i<n; ++i) {
    groups[i].mark.bounds.clear();
  }
  for (i=0; i<n; ++i) {
    g = groups[i];
    g.x += (dx[i] += x);
    g.y += (dy[i] += y);
    bounds.union(g.mark.bounds.union(g.bounds.translate(dx[i], dy[i])));
    if (dirty) view.dirty(g);
  }

  return bounds;
}

function trellisLayout(view, group, opt) {
  var views = gridLayoutGroups(group),
      groups = views.marks,
      bbox = opt.bounds === Flush ? boundFlush : boundFull,
      off = opt.offset,
      ncols = opt.columns || groups.length,
      nrows = ncols < 0 ? 1 : Math.ceil(groups.length / ncols),
      cells = nrows * ncols,
      x, y, x2, y2, anchor, band, offset;

  // -- initial grid layout
  const bounds = gridLayout(view, groups, opt);

  // -- layout grid headers and footers --

  // perform row header layout
  if (views.rowheaders) {
    band = get$2(opt.headerBand, Row, null);
    x = layoutHeaders(view, views.rowheaders, groups, ncols, nrows, -get$2(off, 'rowHeader'), min$1, 0, bbox, 'x1', 0, ncols, 1, band);
  }

  // perform column header layout
  if (views.colheaders) {
    band = get$2(opt.headerBand, Column, null);
    y = layoutHeaders(view, views.colheaders, groups, ncols, ncols, -get$2(off, 'columnHeader'), min$1, 1, bbox, 'y1', 0, 1, ncols, band);
  }

  // perform row footer layout
  if (views.rowfooters) {
    band = get$2(opt.footerBand, Row, null);
    x2 = layoutHeaders(view, views.rowfooters, groups, ncols, nrows,  get$2(off, 'rowFooter'), max$1, 0, bbox, 'x2', ncols-1, ncols, 1, band);
  }

  // perform column footer layout
  if (views.colfooters) {
    band = get$2(opt.footerBand, Column, null);
    y2 = layoutHeaders(view, views.colfooters, groups, ncols, ncols,  get$2(off, 'columnFooter'), max$1, 1, bbox, 'y2', cells-ncols, 1, ncols, band);
  }

  // perform row title layout
  if (views.rowtitle) {
    anchor = get$2(opt.titleAnchor, Row);
    offset = get$2(off, 'rowTitle');
    offset = anchor === End ? x2 + offset : x - offset;
    band = get$2(opt.titleBand, Row, 0.5);
    layoutTitle(view, views.rowtitle, offset, 0, bounds, band);
  }

  // perform column title layout
  if (views.coltitle) {
    anchor = get$2(opt.titleAnchor, Column);
    offset = get$2(off, 'columnTitle');
    offset = anchor === End ? y2 + offset : y - offset;
    band = get$2(opt.titleBand, Column, 0.5);
    layoutTitle(view, views.coltitle, offset, 1, bounds, band);
  }
}

function boundFlush(item, field) {
  return field === 'x1' ? (item.x || 0)
    : field === 'y1' ? (item.y || 0)
    : field === 'x2' ? (item.x || 0) + (item.width || 0)
    : field === 'y2' ? (item.y || 0) + (item.height || 0)
    : undefined;
}

function boundFull(item, field) {
  return item.bounds[field];
}

// aggregation functions for grid margin determination
function min$1(a, b) { return Math.floor(Math.min(a, b)); }
function max$1(a, b) { return Math.ceil(Math.max(a, b)); }

function layoutHeaders(view, headers, groups, ncols, limit, offset, agg, isX, bound, bf, start, stride, back, band) {
  var n = groups.length,
      init = 0,
      edge = 0,
      i, j, k, m, b, h, g, x, y;

  // if no groups, early exit and return 0
  if (!n) return init;

  // compute margin
  for (i=start; i<n; i+=stride) {
    if (groups[i]) init = agg(init, bound(groups[i], bf));
  }

  // if no headers, return margin calculation
  if (!headers.length) return init;

  // check if number of headers exceeds number of rows or columns
  if (headers.length > limit) {
    view.warn('Grid headers exceed limit: ' + limit);
    headers = headers.slice(0, limit);
  }

  // apply offset
  init += offset;

  // clear mark bounds for all headers
  for (j=0, m=headers.length; j<m; ++j) {
    view.dirty(headers[j]);
    headers[j].mark.bounds.clear();
  }

  // layout each header
  for (i=start, j=0, m=headers.length; j<m; ++j, i+=stride) {
    h = headers[j];
    b = h.mark.bounds;

    // search for nearest group to align to
    // necessary if table has empty cells
    for (k=i; k >= 0 && (g = groups[k]) == null; k-=back);

    // assign coordinates and update bounds
    if (isX) {
      x = band == null ? g.x : Math.round(g.bounds.x1 + band * g.bounds.width());
      y = init;
    } else {
      x = init;
      y = band == null ? g.y : Math.round(g.bounds.y1 + band * g.bounds.height());
    }
    b.union(h.bounds.translate(x - (h.x || 0), y - (h.y || 0)));
    h.x = x;
    h.y = y;
    view.dirty(h);

    // update current edge of layout bounds
    edge = agg(edge, b[bf]);
  }

  return edge;
}

function layoutTitle(view, g, offset, isX, bounds, band) {
  if (!g) return;
  view.dirty(g);

  // compute title coordinates
  var x = offset, y = offset;
  isX
    ? (x = Math.round(bounds.x1 + band * bounds.width()))
    : (y = Math.round(bounds.y1 + band * bounds.height()));

  // assign coordinates and update bounds
  g.bounds.translate(x - (g.x || 0), y - (g.y || 0));
  g.mark.bounds.clear().union(g.bounds);
  g.x = x;
  g.y = y;

  // queue title for redraw
  view.dirty(g);
}

// utility for looking up legend layout configuration
function lookup$2(config, orient) {
  const opt = config[orient] || {};
  return (key, d) => opt[key] != null ? opt[key]
    : config[key] != null ? config[key]
    : d;
}

// if legends specify offset directly, use the maximum specified value
function offsets(legends, value) {
  var max = -Infinity;
  legends.forEach(item => {
    if (item.offset != null) max = Math.max(max, item.offset);
  });
  return max > -Infinity ? max : value;
}

function legendParams(g, orient, config, xb, yb, w, h) {
  const _ = lookup$2(config, orient),
        offset = offsets(g, _('offset', 0)),
        anchor = _('anchor', Start),
        mult = anchor === End ? 1 : anchor === Middle ? 0.5 : 0;

  const p = {
    align:   Each,
    bounds:  _('bounds', Flush),
    columns: _('direction') === 'vertical' ? 1 : g.length,
    padding: _('margin', 8),
    center:  _('center'),
    nodirty: true
  };

  switch (orient) {
    case Left:
      p.anchor = {
        x: Math.floor(xb.x1) - offset, column: End,
        y: mult * (h || xb.height() + 2 * xb.y1), row: anchor
      };
      break;
    case Right:
      p.anchor = {
        x: Math.ceil(xb.x2) + offset,
        y: mult * (h || xb.height() + 2 * xb.y1), row: anchor
      };
      break;
    case Top:
      p.anchor = {
        y: Math.floor(yb.y1) - offset, row: End,
        x: mult * (w || yb.width() + 2 * yb.x1), column: anchor
      };
      break;
    case Bottom:
      p.anchor = {
        y: Math.ceil(yb.y2) + offset,
        x: mult * (w || yb.width() + 2 * yb.x1), column: anchor
      };
      break;
    case TopLeft:
      p.anchor = {x: offset, y: offset};
      break;
    case TopRight:
      p.anchor = {x: w - offset, y: offset, column: End};
      break;
    case BottomLeft:
      p.anchor = {x: offset, y: h - offset, row: End};
      break;
    case BottomRight:
      p.anchor = {x: w - offset, y: h - offset, column: End, row: End};
      break;
  }

  return p;
}

function legendLayout(view, legend) {
  var item = legend.items[0],
      datum = item.datum,
      orient = item.orient,
      bounds = item.bounds,
      x = item.x, y = item.y, w, h;

  // cache current bounds for later comparison
  item._bounds
    ? item._bounds.clear().union(bounds)
    : item._bounds = bounds.clone();
  bounds.clear();

  // adjust legend to accommodate padding and title
  legendGroupLayout(view, item, item.items[0].items[0]);

  // aggregate bounds to determine size, and include origin
  bounds = legendBounds(item, bounds);
  w = 2 * item.padding;
  h = 2 * item.padding;
  if (!bounds.empty()) {
    w = Math.ceil(bounds.width() + w);
    h = Math.ceil(bounds.height() + h);
  }

  if (datum.type === Symbols) {
    legendEntryLayout(item.items[0].items[0].items[0].items);
  }

  if (orient !== None$1) {
    item.x = x = 0;
    item.y = y = 0;
  }
  item.width = w;
  item.height = h;
  boundStroke(bounds.set(x, y, x + w, y + h), item);
  item.mark.bounds.clear().union(bounds);

  return item;
}

function legendBounds(item, b) {
  // aggregate item bounds
  item.items.forEach(_ => b.union(_.bounds));

  // anchor to legend origin
  b.x1 = item.padding;
  b.y1 = item.padding;

  return b;
}

function legendGroupLayout(view, item, entry) {
  var pad = item.padding,
      ex = pad - entry.x,
      ey = pad - entry.y;

  if (!item.datum.title) {
    if (ex || ey) translate$2(view, entry, ex, ey);
  } else {
    var title = item.items[1].items[0],
        anchor = title.anchor,
        tpad = item.titlePadding || 0,
        tx = pad - title.x,
        ty = pad - title.y;

    switch (title.orient) {
      case Left:
        ex += Math.ceil(title.bounds.width()) + tpad;
        break;
      case Right:
      case Bottom:
        break;
      default:
        ey += title.bounds.height() + tpad;
    }
    if (ex || ey) translate$2(view, entry, ex, ey);

    switch (title.orient) {
      case Left:
        ty += legendTitleOffset(item, entry, title, anchor, 1, 1);
        break;
      case Right:
        tx += legendTitleOffset(item, entry, title, End, 0, 0) + tpad;
        ty += legendTitleOffset(item, entry, title, anchor, 1, 1);
        break;
      case Bottom:
        tx += legendTitleOffset(item, entry, title, anchor, 0, 0);
        ty += legendTitleOffset(item, entry, title, End, -1, 0, 1) + tpad;
        break;
      default:
        tx += legendTitleOffset(item, entry, title, anchor, 0, 0);
    }
    if (tx || ty) translate$2(view, title, tx, ty);

    // translate legend if title pushes into negative coordinates
    if ((tx = Math.round(title.bounds.x1 - pad)) < 0) {
      translate$2(view, entry, -tx, 0);
      translate$2(view, title, -tx, 0);
    }
  }
}

function legendTitleOffset(item, entry, title, anchor, y, lr, noBar) {
  const grad = item.datum.type !== 'symbol',
        vgrad = title.datum.vgrad,
        e = grad && (lr || !vgrad) && !noBar ? entry.items[0] : entry,
        s = e.bounds[y ? 'y2' : 'x2'] - item.padding,
        u = vgrad && lr ? s : 0,
        v = vgrad && lr ? 0 : s,
        o = y <= 0 ? 0 : multiLineOffset(title);

  return Math.round(anchor === Start ? u
    : anchor === End ? (v - o)
    : 0.5 * (s - o));
}

function translate$2(view, item, dx, dy) {
  item.x += dx;
  item.y += dy;
  item.bounds.translate(dx, dy);
  item.mark.bounds.translate(dx, dy);
  view.dirty(item);
}

function legendEntryLayout(entries) {
  // get max widths for each column
  var widths = entries.reduce(function(w, g) {
    w[g.column] = Math.max(g.bounds.x2 - g.x, w[g.column] || 0);
    return w;
  }, {});

  // set dimensions of legend entry groups
  entries.forEach(function(g) {
    g.width  = widths[g.column];
    g.height = g.bounds.y2 - g.y;
  });
}

function titleLayout(view, mark, width, height, viewBounds) {
  var group = mark.items[0],
      frame = group.frame,
      orient = group.orient,
      anchor = group.anchor,
      offset = group.offset,
      padding = group.padding,
      title = group.items[0].items[0],
      subtitle = group.items[1] && group.items[1].items[0],
      end = (orient === Left || orient === Right) ? height : width,
      start = 0, x = 0, y = 0, sx = 0, sy = 0, pos;

  if (frame !== Group) {
    orient === Left ? (start = viewBounds.y2, end = viewBounds.y1)
      : orient === Right ? (start = viewBounds.y1, end = viewBounds.y2)
      : (start = viewBounds.x1, end = viewBounds.x2);
  } else if (orient === Left) {
    start = height, end = 0;
  }

  pos = (anchor === Start) ? start
    : (anchor === End) ? end
    : (start + end) / 2;

  if (subtitle && subtitle.text) {
    // position subtitle
    switch (orient) {
      case Top:
      case Bottom:
        sy = title.bounds.height() + padding;
        break;
      case Left:
        sx = title.bounds.width() + padding;
        break;
      case Right:
        sx = -title.bounds.width() - padding;
        break;
    }

    tempBounds$2.clear().union(subtitle.bounds);
    tempBounds$2.translate(sx - (subtitle.x || 0), sy - (subtitle.y || 0));
    if (set(subtitle, 'x', sx) | set(subtitle, 'y', sy)) {
      view.dirty(subtitle);
      subtitle.bounds.clear().union(tempBounds$2);
      subtitle.mark.bounds.clear().union(tempBounds$2);
      view.dirty(subtitle);
    }

    tempBounds$2.clear().union(subtitle.bounds);
  } else {
    tempBounds$2.clear();
  }
  tempBounds$2.union(title.bounds);

  // position title group
  switch (orient) {
    case Top:
      x = pos;
      y = viewBounds.y1 - tempBounds$2.height() - offset;
      break;
    case Left:
      x = viewBounds.x1 - tempBounds$2.width() - offset;
      y = pos;
      break;
    case Right:
      x = viewBounds.x2 + tempBounds$2.width() + offset;
      y = pos;
      break;
    case Bottom:
      x = pos;
      y = viewBounds.y2 + offset;
      break;
    default:
      x = group.x;
      y = group.y;
  }

  if (set(group, 'x', x) | set(group, 'y', y)) {
    tempBounds$2.translate(x, y);
    view.dirty(group);
    group.bounds.clear().union(tempBounds$2);
    mark.bounds.clear().union(tempBounds$2);
    view.dirty(group);
  }
  return group.bounds;
}

/**
 * Layout view elements such as axes and legends.
 * Also performs size adjustments.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {object} params.mark - Scenegraph mark of groups to layout.
 */
function ViewLayout(params) {
  Transform.call(this, null, params);
}

var prototype$V = inherits(ViewLayout, Transform);

prototype$V.transform = function(_, pulse) {
  // TODO incremental update, output?
  var view = pulse.dataflow;
  _.mark.items.forEach(function(group) {
    if (_.layout) trellisLayout(view, group, _.layout);
    layoutGroup(view, group, _);
  });
  if (_.modified()) pulse.reflow();
  return pulse;
};

function layoutGroup(view, group, _) {
  var items = group.items,
      width = Math.max(0, group.width || 0),
      height = Math.max(0, group.height || 0),
      viewBounds = new Bounds().set(0, 0, width, height),
      xBounds = viewBounds.clone(),
      yBounds = viewBounds.clone(),
      legends = [], title,
      mark, orient, b, i, n;

  // layout axes, gather legends, collect bounds
  for (i=0, n=items.length; i<n; ++i) {
    mark = items[i];
    switch (mark.role) {
      case AxisRole:
        b = isYAxis(mark) ? xBounds : yBounds;
        b.union(axisLayout(view, mark, width, height));
        break;
      case TitleRole:
        title = mark;
        break;
      case LegendRole:
        legends.push(legendLayout(view, mark));
        break;
      case FrameRole:
      case ScopeRole:
      case RowHeader:
      case RowFooter:
      case RowTitle:
      case ColHeader:
      case ColFooter:
      case ColTitle:
        xBounds.union(mark.bounds);
        yBounds.union(mark.bounds);
        break;
      default:
        viewBounds.union(mark.bounds);
    }
  }

  // layout legends, adjust viewBounds
  if (legends.length) {
    // group legends by orient
    const l = {};
    legends.forEach(item => {
      orient = item.orient || Right;
      if (orient !== None$1) (l[orient] || (l[orient] = [])).push(item);
    });

    // perform grid layout for each orient group
    for (let orient in l) {
      const g = l[orient];
      gridLayout(view, g, legendParams(
        g, orient, _.legends, xBounds, yBounds, width, height
      ));
    }

    // update view bounds
    legends.forEach(item => {
      const b = item.bounds;

      if (!b.equals(item._bounds)) {
        item.bounds = item._bounds;
        view.dirty(item); // dirty previous location
        item.bounds = b;
        view.dirty(item);
      }

      if (_.autosize && _.autosize.type === Fit) {
        // For autosize fit, incorporate the orthogonal dimension only.
        // Legends that overrun the chart area will then be clipped;
        // otherwise the chart area gets reduced to nothing!
        switch(item.orient) {
          case Left:
          case Right:
            viewBounds.add(b.x1, 0).add(b.x2, 0);
            break;
          case Top:
          case Bottom:
            viewBounds.add(0, b.y1).add(0, b.y2);
        }
      } else {
        viewBounds.union(b);
      }
    });
  }

  // combine bounding boxes
  viewBounds.union(xBounds).union(yBounds);

  // layout title, adjust bounds
  if (title) {
    viewBounds.union(titleLayout(view, title, width, height, viewBounds));
  }

  // override aggregated view bounds if content is clipped
  if (group.clip) {
    viewBounds.set(0, 0, group.width || 0, group.height || 0);
  }

  // perform size adjustment
  viewSizeLayout(view, group, viewBounds, _);
}

function viewSizeLayout(view, group, viewBounds, _) {
  var auto = _.autosize || {},
      type = auto.type,
      viewWidth = view._width,
      viewHeight = view._height,
      padding = view.padding();

  if (view._autosize < 1 || !type) return;

  var width  = Math.max(0, group.width || 0),
      left   = Math.max(0, Math.ceil(-viewBounds.x1)),
      right  = Math.max(0, Math.ceil(viewBounds.x2 - width)),
      height = Math.max(0, group.height || 0),
      top    = Math.max(0, Math.ceil(-viewBounds.y1)),
      bottom = Math.max(0, Math.ceil(viewBounds.y2 - height));

  if (auto.contains === Padding) {
    viewWidth -= padding.left + padding.right;
    viewHeight -= padding.top + padding.bottom;
  }

  if (type === None$1) {
    left = 0;
    top = 0;
    width = viewWidth;
    height = viewHeight;
  }

  else if (type === Fit) {
    width = Math.max(0, viewWidth - left - right);
    height = Math.max(0, viewHeight - top - bottom);
  }

  else if (type === FitX) {
    width = Math.max(0, viewWidth - left - right);
    viewHeight = height + top + bottom;
  }

  else if (type === FitY) {
    viewWidth = width + left + right;
    height = Math.max(0, viewHeight - top - bottom);
  }

  else if (type === Pad) {
    viewWidth = width + left + right;
    viewHeight = height + top + bottom;
  }

  view._resizeView(
    viewWidth, viewHeight,
    width, height,
    [left, top],
    auto.resize
  );
}



var vtx = /*#__PURE__*/Object.freeze({
  __proto__: null,
  bound: Bound,
  identifier: Identifier,
  mark: Mark,
  overlap: Overlap,
  render: Render,
  viewlayout: ViewLayout
});

function bandSpace(count, paddingInner, paddingOuter) {
  var space = count - paddingInner + paddingOuter * 2;
  return count ? (space > 0 ? space : 1) : 0;
}

const Identity = 'identity';

const Linear = 'linear';
const Log = 'log';
const Pow = 'pow';
const Sqrt = 'sqrt';
const Symlog = 'symlog';

const Time = 'time';
const UTC = 'utc';

const Sequential = 'sequential';
const Diverging = 'diverging';

const Quantile$1 = 'quantile';
const Quantize = 'quantize';
const Threshold = 'threshold';

const Ordinal = 'ordinal';
const Point = 'point';
const Band = 'band';
const BinOrdinal = 'bin-ordinal';

// categories
const Continuous = 'continuous';
const Discrete = 'discrete';
const Discretizing = 'discretizing';
const Interpolating = 'interpolating';
const Temporal = 'temporal';

function invertRange(scale) {
  return function(_) {
    var lo = _[0],
        hi = _[1],
        t;

    if (hi < lo) {
      t = lo;
      lo = hi;
      hi = t;
    }

    return [
      scale.invert(lo),
      scale.invert(hi)
    ];
  }
}

function invertRangeExtent(scale) {
  return function(_) {
    var range = scale.range(),
        lo = _[0],
        hi = _[1],
        min = -1, max, t, i, n;

    if (hi < lo) {
      t = lo;
      lo = hi;
      hi = t;
    }

    for (i=0, n=range.length; i<n; ++i) {
      if (range[i] >= lo && range[i] <= hi) {
        if (min < 0) min = i;
        max = i;
      }
    }

    if (min < 0) return undefined;

    lo = scale.invertExtent(range[min]);
    hi = scale.invertExtent(range[max]);

    return [
      lo[0] === undefined ? lo[1] : lo[0],
      hi[1] === undefined ? hi[0] : hi[1]
    ];
  }
}

function initRange(domain, range) {
  switch (arguments.length) {
    case 0: break;
    case 1: this.range(domain); break;
    default: this.range(range).domain(domain); break;
  }
  return this;
}

function initInterpolator(domain, interpolator) {
  switch (arguments.length) {
    case 0: break;
    case 1: {
      if (typeof domain === "function") this.interpolator(domain);
      else this.range(domain);
      break;
    }
    default: {
      this.domain(domain);
      if (typeof interpolator === "function") this.interpolator(interpolator);
      else this.range(interpolator);
      break;
    }
  }
  return this;
}

const implicit = Symbol("implicit");

function ordinal() {
  var index = new Map(),
      domain = [],
      range = [],
      unknown = implicit;

  function scale(d) {
    var key = d + "", i = index.get(key);
    if (!i) {
      if (unknown !== implicit) return unknown;
      index.set(key, i = domain.push(d));
    }
    return range[(i - 1) % range.length];
  }

  scale.domain = function(_) {
    if (!arguments.length) return domain.slice();
    domain = [], index = new Map();
    for (const value of _) {
      const key = value + "";
      if (index.has(key)) continue;
      index.set(key, domain.push(value));
    }
    return scale;
  };

  scale.range = function(_) {
    return arguments.length ? (range = Array.from(_), scale) : range.slice();
  };

  scale.unknown = function(_) {
    return arguments.length ? (unknown = _, scale) : unknown;
  };

  scale.copy = function() {
    return ordinal(domain, range).unknown(unknown);
  };

  initRange.apply(scale, arguments);

  return scale;
}

function constant$1(x) {
  return function() {
    return x;
  };
}

function number$2(x) {
  return +x;
}

var unit = [0, 1];

function identity$1(x) {
  return x;
}

function normalize(a, b) {
  return (b -= (a = +a))
      ? function(x) { return (x - a) / b; }
      : constant$1(isNaN(b) ? NaN : 0.5);
}

function clamper(a, b) {
  var t;
  if (a > b) t = a, a = b, b = t;
  return function(x) { return Math.max(a, Math.min(b, x)); };
}

// normalize(a, b)(x) takes a domain value x in [a,b] and returns the corresponding parameter t in [0,1].
// interpolate(a, b)(t) takes a parameter t in [0,1] and returns the corresponding range value x in [a,b].
function bimap(domain, range, interpolate) {
  var d0 = domain[0], d1 = domain[1], r0 = range[0], r1 = range[1];
  if (d1 < d0) d0 = normalize(d1, d0), r0 = interpolate(r1, r0);
  else d0 = normalize(d0, d1), r0 = interpolate(r0, r1);
  return function(x) { return r0(d0(x)); };
}

function polymap(domain, range, interpolate) {
  var j = Math.min(domain.length, range.length) - 1,
      d = new Array(j),
      r = new Array(j),
      i = -1;

  // Reverse descending domains.
  if (domain[j] < domain[0]) {
    domain = domain.slice().reverse();
    range = range.slice().reverse();
  }

  while (++i < j) {
    d[i] = normalize(domain[i], domain[i + 1]);
    r[i] = interpolate(range[i], range[i + 1]);
  }

  return function(x) {
    var i = bisectRight(domain, x, 1, j) - 1;
    return r[i](d[i](x));
  };
}

function copy(source, target) {
  return target
      .domain(source.domain())
      .range(source.range())
      .interpolate(source.interpolate())
      .clamp(source.clamp())
      .unknown(source.unknown());
}

function transformer() {
  var domain = unit,
      range = unit,
      interpolate = interpolate$1,
      transform,
      untransform,
      unknown,
      clamp = identity$1,
      piecewise,
      output,
      input;

  function rescale() {
    var n = Math.min(domain.length, range.length);
    if (clamp !== identity$1) clamp = clamper(domain[0], domain[n - 1]);
    piecewise = n > 2 ? polymap : bimap;
    output = input = null;
    return scale;
  }

  function scale(x) {
    return isNaN(x = +x) ? unknown : (output || (output = piecewise(domain.map(transform), range, interpolate)))(transform(clamp(x)));
  }

  scale.invert = function(y) {
    return clamp(untransform((input || (input = piecewise(range, domain.map(transform), interpolateNumber)))(y)));
  };

  scale.domain = function(_) {
    return arguments.length ? (domain = Array.from(_, number$2), rescale()) : domain.slice();
  };

  scale.range = function(_) {
    return arguments.length ? (range = Array.from(_), rescale()) : range.slice();
  };

  scale.rangeRound = function(_) {
    return range = Array.from(_), interpolate = interpolateRound, rescale();
  };

  scale.clamp = function(_) {
    return arguments.length ? (clamp = _ ? true : identity$1, rescale()) : clamp !== identity$1;
  };

  scale.interpolate = function(_) {
    return arguments.length ? (interpolate = _, rescale()) : interpolate;
  };

  scale.unknown = function(_) {
    return arguments.length ? (unknown = _, scale) : unknown;
  };

  return function(t, u) {
    transform = t, untransform = u;
    return rescale();
  };
}

function continuous() {
  return transformer()(identity$1, identity$1);
}

function spanFormat(start, stop, count, specifier) {
  var step = tickStep(start, stop, count),
      precision;
  specifier = formatSpecifier(specifier == null ? ",f" : specifier);
  switch (specifier.type) {
    case "s": {
      var value = Math.max(Math.abs(start), Math.abs(stop));
      if (specifier.precision == null && !isNaN(precision = precisionPrefix(step, value))) specifier.precision = precision;
      return formatPrefix(specifier, value);
    }
    case "":
    case "e":
    case "g":
    case "p":
    case "r": {
      if (specifier.precision == null && !isNaN(precision = precisionRound(step, Math.max(Math.abs(start), Math.abs(stop))))) specifier.precision = precision - (specifier.type === "e");
      break;
    }
    case "f":
    case "%": {
      if (specifier.precision == null && !isNaN(precision = precisionFixed(step))) specifier.precision = precision - (specifier.type === "%") * 2;
      break;
    }
  }
  return format$2(specifier);
}

function linearish(scale) {
  var domain = scale.domain;

  scale.ticks = function(count) {
    var d = domain();
    return ticks(d[0], d[d.length - 1], count == null ? 10 : count);
  };

  scale.tickFormat = function(count, specifier) {
    var d = domain();
    return spanFormat(d[0], d[d.length - 1], count == null ? 10 : count, specifier);
  };

  scale.nice = function(count) {
    if (count == null) count = 10;

    var d = domain(),
        i0 = 0,
        i1 = d.length - 1,
        start = d[i0],
        stop = d[i1],
        step;

    if (stop < start) {
      step = start, start = stop, stop = step;
      step = i0, i0 = i1, i1 = step;
    }

    step = tickIncrement(start, stop, count);

    if (step > 0) {
      start = Math.floor(start / step) * step;
      stop = Math.ceil(stop / step) * step;
      step = tickIncrement(start, stop, count);
    } else if (step < 0) {
      start = Math.ceil(start * step) / step;
      stop = Math.floor(stop * step) / step;
      step = tickIncrement(start, stop, count);
    }

    if (step > 0) {
      d[i0] = Math.floor(start / step) * step;
      d[i1] = Math.ceil(stop / step) * step;
      domain(d);
    } else if (step < 0) {
      d[i0] = Math.ceil(start * step) / step;
      d[i1] = Math.floor(stop * step) / step;
      domain(d);
    }

    return scale;
  };

  return scale;
}

function linear() {
  var scale = continuous();

  scale.copy = function() {
    return copy(scale, linear());
  };

  initRange.apply(scale, arguments);

  return linearish(scale);
}

function identity$2(domain) {
  var unknown;

  function scale(x) {
    return isNaN(x = +x) ? unknown : x;
  }

  scale.invert = scale;

  scale.domain = scale.range = function(_) {
    return arguments.length ? (domain = Array.from(_, number$2), scale) : domain.slice();
  };

  scale.unknown = function(_) {
    return arguments.length ? (unknown = _, scale) : unknown;
  };

  scale.copy = function() {
    return identity$2(domain).unknown(unknown);
  };

  domain = arguments.length ? Array.from(domain, number$2) : [0, 1];

  return linearish(scale);
}

function nice(domain, interval) {
  domain = domain.slice();

  var i0 = 0,
      i1 = domain.length - 1,
      x0 = domain[i0],
      x1 = domain[i1],
      t;

  if (x1 < x0) {
    t = i0, i0 = i1, i1 = t;
    t = x0, x0 = x1, x1 = t;
  }

  domain[i0] = interval.floor(x0);
  domain[i1] = interval.ceil(x1);
  return domain;
}

function transformLog(x) {
  return Math.log(x);
}

function transformExp(x) {
  return Math.exp(x);
}

function transformLogn(x) {
  return -Math.log(-x);
}

function transformExpn(x) {
  return -Math.exp(-x);
}

function pow10(x) {
  return isFinite(x) ? +("1e" + x) : x < 0 ? 0 : x;
}

function powp(base) {
  return base === 10 ? pow10
      : base === Math.E ? Math.exp
      : function(x) { return Math.pow(base, x); };
}

function logp(base) {
  return base === Math.E ? Math.log
      : base === 10 && Math.log10
      || base === 2 && Math.log2
      || (base = Math.log(base), function(x) { return Math.log(x) / base; });
}

function reflect(f) {
  return function(x) {
    return -f(-x);
  };
}

function loggish(transform) {
  var scale = transform(transformLog, transformExp),
      domain = scale.domain,
      base = 10,
      logs,
      pows;

  function rescale() {
    logs = logp(base), pows = powp(base);
    if (domain()[0] < 0) {
      logs = reflect(logs), pows = reflect(pows);
      transform(transformLogn, transformExpn);
    } else {
      transform(transformLog, transformExp);
    }
    return scale;
  }

  scale.base = function(_) {
    return arguments.length ? (base = +_, rescale()) : base;
  };

  scale.domain = function(_) {
    return arguments.length ? (domain(_), rescale()) : domain();
  };

  scale.ticks = function(count) {
    var d = domain(),
        u = d[0],
        v = d[d.length - 1],
        r;

    if (r = v < u) i = u, u = v, v = i;

    var i = logs(u),
        j = logs(v),
        p,
        k,
        t,
        n = count == null ? 10 : +count,
        z = [];

    if (!(base % 1) && j - i < n) {
      i = Math.floor(i), j = Math.ceil(j);
      if (u > 0) for (; i <= j; ++i) {
        for (k = 1, p = pows(i); k < base; ++k) {
          t = p * k;
          if (t < u) continue;
          if (t > v) break;
          z.push(t);
        }
      } else for (; i <= j; ++i) {
        for (k = base - 1, p = pows(i); k >= 1; --k) {
          t = p * k;
          if (t < u) continue;
          if (t > v) break;
          z.push(t);
        }
      }
      if (z.length * 2 < n) z = ticks(u, v, n);
    } else {
      z = ticks(i, j, Math.min(j - i, n)).map(pows);
    }

    return r ? z.reverse() : z;
  };

  scale.tickFormat = function(count, specifier) {
    if (specifier == null) specifier = base === 10 ? ".0e" : ",";
    if (typeof specifier !== "function") specifier = format$2(specifier);
    if (count === Infinity) return specifier;
    if (count == null) count = 10;
    var k = Math.max(1, base * count / scale.ticks().length); // TODO fast estimate?
    return function(d) {
      var i = d / pows(Math.round(logs(d)));
      if (i * base < base - 0.5) i *= base;
      return i <= k ? specifier(d) : "";
    };
  };

  scale.nice = function() {
    return domain(nice(domain(), {
      floor: function(x) { return pows(Math.floor(logs(x))); },
      ceil: function(x) { return pows(Math.ceil(logs(x))); }
    }));
  };

  return scale;
}

function log$2() {
  var scale = loggish(transformer()).domain([1, 10]);

  scale.copy = function() {
    return copy(scale, log$2()).base(scale.base());
  };

  initRange.apply(scale, arguments);

  return scale;
}

function transformSymlog(c) {
  return function(x) {
    return Math.sign(x) * Math.log1p(Math.abs(x / c));
  };
}

function transformSymexp(c) {
  return function(x) {
    return Math.sign(x) * Math.expm1(Math.abs(x)) * c;
  };
}

function symlogish(transform) {
  var c = 1, scale = transform(transformSymlog(c), transformSymexp(c));

  scale.constant = function(_) {
    return arguments.length ? transform(transformSymlog(c = +_), transformSymexp(c)) : c;
  };

  return linearish(scale);
}

function symlog$1() {
  var scale = symlogish(transformer());

  scale.copy = function() {
    return copy(scale, symlog$1()).constant(scale.constant());
  };

  return initRange.apply(scale, arguments);
}

function transformPow(exponent) {
  return function(x) {
    return x < 0 ? -Math.pow(-x, exponent) : Math.pow(x, exponent);
  };
}

function transformSqrt(x) {
  return x < 0 ? -Math.sqrt(-x) : Math.sqrt(x);
}

function transformSquare(x) {
  return x < 0 ? -x * x : x * x;
}

function powish(transform) {
  var scale = transform(identity$1, identity$1),
      exponent = 1;

  function rescale() {
    return exponent === 1 ? transform(identity$1, identity$1)
        : exponent === 0.5 ? transform(transformSqrt, transformSquare)
        : transform(transformPow(exponent), transformPow(1 / exponent));
  }

  scale.exponent = function(_) {
    return arguments.length ? (exponent = +_, rescale()) : exponent;
  };

  return linearish(scale);
}

function pow$1() {
  var scale = powish(transformer());

  scale.copy = function() {
    return copy(scale, pow$1()).exponent(scale.exponent());
  };

  initRange.apply(scale, arguments);

  return scale;
}

function sqrt() {
  return pow$1.apply(null, arguments).exponent(0.5);
}

function quantile$1() {
  var domain = [],
      range = [],
      thresholds = [],
      unknown;

  function rescale() {
    var i = 0, n = Math.max(1, range.length);
    thresholds = new Array(n - 1);
    while (++i < n) thresholds[i - 1] = quantile(domain, i / n);
    return scale;
  }

  function scale(x) {
    return isNaN(x = +x) ? unknown : range[bisectRight(thresholds, x)];
  }

  scale.invertExtent = function(y) {
    var i = range.indexOf(y);
    return i < 0 ? [NaN, NaN] : [
      i > 0 ? thresholds[i - 1] : domain[0],
      i < thresholds.length ? thresholds[i] : domain[domain.length - 1]
    ];
  };

  scale.domain = function(_) {
    if (!arguments.length) return domain.slice();
    domain = [];
    for (let d of _) if (d != null && !isNaN(d = +d)) domain.push(d);
    domain.sort(ascending);
    return rescale();
  };

  scale.range = function(_) {
    return arguments.length ? (range = Array.from(_), rescale()) : range.slice();
  };

  scale.unknown = function(_) {
    return arguments.length ? (unknown = _, scale) : unknown;
  };

  scale.quantiles = function() {
    return thresholds.slice();
  };

  scale.copy = function() {
    return quantile$1()
        .domain(domain)
        .range(range)
        .unknown(unknown);
  };

  return initRange.apply(scale, arguments);
}

function quantize() {
  var x0 = 0,
      x1 = 1,
      n = 1,
      domain = [0.5],
      range = [0, 1],
      unknown;

  function scale(x) {
    return x <= x ? range[bisectRight(domain, x, 0, n)] : unknown;
  }

  function rescale() {
    var i = -1;
    domain = new Array(n);
    while (++i < n) domain[i] = ((i + 1) * x1 - (i - n) * x0) / (n + 1);
    return scale;
  }

  scale.domain = function(_) {
    return arguments.length ? ([x0, x1] = _, x0 = +x0, x1 = +x1, rescale()) : [x0, x1];
  };

  scale.range = function(_) {
    return arguments.length ? (n = (range = Array.from(_)).length - 1, rescale()) : range.slice();
  };

  scale.invertExtent = function(y) {
    var i = range.indexOf(y);
    return i < 0 ? [NaN, NaN]
        : i < 1 ? [x0, domain[0]]
        : i >= n ? [domain[n - 1], x1]
        : [domain[i - 1], domain[i]];
  };

  scale.unknown = function(_) {
    return arguments.length ? (unknown = _, scale) : scale;
  };

  scale.thresholds = function() {
    return domain.slice();
  };

  scale.copy = function() {
    return quantize()
        .domain([x0, x1])
        .range(range)
        .unknown(unknown);
  };

  return initRange.apply(linearish(scale), arguments);
}

function threshold() {
  var domain = [0.5],
      range = [0, 1],
      unknown,
      n = 1;

  function scale(x) {
    return x <= x ? range[bisectRight(domain, x, 0, n)] : unknown;
  }

  scale.domain = function(_) {
    return arguments.length ? (domain = Array.from(_), n = Math.min(domain.length, range.length - 1), scale) : domain.slice();
  };

  scale.range = function(_) {
    return arguments.length ? (range = Array.from(_), n = Math.min(domain.length, range.length - 1), scale) : range.slice();
  };

  scale.invertExtent = function(y) {
    var i = range.indexOf(y);
    return [domain[i - 1], domain[i]];
  };

  scale.unknown = function(_) {
    return arguments.length ? (unknown = _, scale) : unknown;
  };

  scale.copy = function() {
    return threshold()
        .domain(domain)
        .range(range)
        .unknown(unknown);
  };

  return initRange.apply(scale, arguments);
}

var durationSecond$1 = 1000,
    durationMinute$1 = durationSecond$1 * 60,
    durationHour$1 = durationMinute$1 * 60,
    durationDay$1 = durationHour$1 * 24,
    durationWeek$1 = durationDay$1 * 7,
    durationMonth$1 = durationDay$1 * 30,
    durationYear$1 = durationDay$1 * 365;

function date(t) {
  return new Date(t);
}

function number$3(t) {
  return t instanceof Date ? +t : +new Date(+t);
}

function calendar(year, month, week, day, hour, minute, second, millisecond, format) {
  var scale = continuous(),
      invert = scale.invert,
      domain = scale.domain;

  var formatMillisecond = format(".%L"),
      formatSecond = format(":%S"),
      formatMinute = format("%I:%M"),
      formatHour = format("%I %p"),
      formatDay = format("%a %d"),
      formatWeek = format("%b %d"),
      formatMonth = format("%B"),
      formatYear = format("%Y");

  var tickIntervals = [
    [second,  1,      durationSecond$1],
    [second,  5,  5 * durationSecond$1],
    [second, 15, 15 * durationSecond$1],
    [second, 30, 30 * durationSecond$1],
    [minute,  1,      durationMinute$1],
    [minute,  5,  5 * durationMinute$1],
    [minute, 15, 15 * durationMinute$1],
    [minute, 30, 30 * durationMinute$1],
    [  hour,  1,      durationHour$1  ],
    [  hour,  3,  3 * durationHour$1  ],
    [  hour,  6,  6 * durationHour$1  ],
    [  hour, 12, 12 * durationHour$1  ],
    [   day,  1,      durationDay$1   ],
    [   day,  2,  2 * durationDay$1   ],
    [  week,  1,      durationWeek$1  ],
    [ month,  1,      durationMonth$1 ],
    [ month,  3,  3 * durationMonth$1 ],
    [  year,  1,      durationYear$1  ]
  ];

  function tickFormat(date) {
    return (second(date) < date ? formatMillisecond
        : minute(date) < date ? formatSecond
        : hour(date) < date ? formatMinute
        : day(date) < date ? formatHour
        : month(date) < date ? (week(date) < date ? formatDay : formatWeek)
        : year(date) < date ? formatMonth
        : formatYear)(date);
  }

  function tickInterval(interval, start, stop) {
    if (interval == null) interval = 10;

    // If a desired tick count is specified, pick a reasonable tick interval
    // based on the extent of the domain and a rough estimate of tick size.
    // Otherwise, assume interval is already a time interval and use it.
    if (typeof interval === "number") {
      var target = Math.abs(stop - start) / interval,
          i = bisector(function(i) { return i[2]; }).right(tickIntervals, target),
          step;
      if (i === tickIntervals.length) {
        step = tickStep(start / durationYear$1, stop / durationYear$1, interval);
        interval = year;
      } else if (i) {
        i = tickIntervals[target / tickIntervals[i - 1][2] < tickIntervals[i][2] / target ? i - 1 : i];
        step = i[1];
        interval = i[0];
      } else {
        step = Math.max(tickStep(start, stop, interval), 1);
        interval = millisecond;
      }
      return interval.every(step);
    }

    return interval;
  }

  scale.invert = function(y) {
    return new Date(invert(y));
  };

  scale.domain = function(_) {
    return arguments.length ? domain(Array.from(_, number$3)) : domain().map(date);
  };

  scale.ticks = function(interval) {
    var d = domain(),
        t0 = d[0],
        t1 = d[d.length - 1],
        r = t1 < t0,
        t;
    if (r) t = t0, t0 = t1, t1 = t;
    t = tickInterval(interval, t0, t1);
    t = t ? t.range(t0, t1 + 1) : []; // inclusive stop
    return r ? t.reverse() : t;
  };

  scale.tickFormat = function(count, specifier) {
    return specifier == null ? tickFormat : format(specifier);
  };

  scale.nice = function(interval) {
    var d = domain();
    return (interval = tickInterval(interval, d[0], d[d.length - 1]))
        ? domain(nice(d, interval))
        : scale;
  };

  scale.copy = function() {
    return copy(scale, calendar(year, month, week, day, hour, minute, second, millisecond, format));
  };

  return scale;
}

function time() {
  return initRange.apply(calendar(timeYear, timeMonth, timeWeek, timeDay, timeHour, timeMinute, timeSecond, timeMillisecond, timeFormat$2).domain([new Date(2000, 0, 1), new Date(2000, 0, 2)]), arguments);
}

function utcTime() {
  return initRange.apply(calendar(utcYear, utcMonth, utcWeek, utcDay, utcHour, utcMinute, utcSecond, utcMillisecond, utcFormat$2).domain([Date.UTC(2000, 0, 1), Date.UTC(2000, 0, 2)]), arguments);
}

function transformer$1() {
  var x0 = 0,
      x1 = 1,
      t0,
      t1,
      k10,
      transform,
      interpolator = identity$1,
      clamp = false,
      unknown;

  function scale(x) {
    return isNaN(x = +x) ? unknown : interpolator(k10 === 0 ? 0.5 : (x = (transform(x) - t0) * k10, clamp ? Math.max(0, Math.min(1, x)) : x));
  }

  scale.domain = function(_) {
    return arguments.length ? ([x0, x1] = _, t0 = transform(x0 = +x0), t1 = transform(x1 = +x1), k10 = t0 === t1 ? 0 : 1 / (t1 - t0), scale) : [x0, x1];
  };

  scale.clamp = function(_) {
    return arguments.length ? (clamp = !!_, scale) : clamp;
  };

  scale.interpolator = function(_) {
    return arguments.length ? (interpolator = _, scale) : interpolator;
  };

  function range(interpolate) {
    return function(_) {
      var r0, r1;
      return arguments.length ? ([r0, r1] = _, interpolator = interpolate(r0, r1), scale) : [interpolator(0), interpolator(1)];
    };
  }

  scale.range = range(interpolate$1);

  scale.rangeRound = range(interpolateRound);

  scale.unknown = function(_) {
    return arguments.length ? (unknown = _, scale) : unknown;
  };

  return function(t) {
    transform = t, t0 = t(x0), t1 = t(x1), k10 = t0 === t1 ? 0 : 1 / (t1 - t0);
    return scale;
  };
}

function copy$1(source, target) {
  return target
      .domain(source.domain())
      .interpolator(source.interpolator())
      .clamp(source.clamp())
      .unknown(source.unknown());
}

function sequential() {
  var scale = linearish(transformer$1()(identity$1));

  scale.copy = function() {
    return copy$1(scale, sequential());
  };

  return initInterpolator.apply(scale, arguments);
}

function sequentialLog() {
  var scale = loggish(transformer$1()).domain([1, 10]);

  scale.copy = function() {
    return copy$1(scale, sequentialLog()).base(scale.base());
  };

  return initInterpolator.apply(scale, arguments);
}

function sequentialSymlog() {
  var scale = symlogish(transformer$1());

  scale.copy = function() {
    return copy$1(scale, sequentialSymlog()).constant(scale.constant());
  };

  return initInterpolator.apply(scale, arguments);
}

function sequentialPow() {
  var scale = powish(transformer$1());

  scale.copy = function() {
    return copy$1(scale, sequentialPow()).exponent(scale.exponent());
  };

  return initInterpolator.apply(scale, arguments);
}

function sequentialSqrt() {
  return sequentialPow.apply(null, arguments).exponent(0.5);
}

function transformer$2() {
  var x0 = 0,
      x1 = 0.5,
      x2 = 1,
      s = 1,
      t0,
      t1,
      t2,
      k10,
      k21,
      interpolator = identity$1,
      transform,
      clamp = false,
      unknown;

  function scale(x) {
    return isNaN(x = +x) ? unknown : (x = 0.5 + ((x = +transform(x)) - t1) * (s * x < s * t1 ? k10 : k21), interpolator(clamp ? Math.max(0, Math.min(1, x)) : x));
  }

  scale.domain = function(_) {
    return arguments.length ? ([x0, x1, x2] = _, t0 = transform(x0 = +x0), t1 = transform(x1 = +x1), t2 = transform(x2 = +x2), k10 = t0 === t1 ? 0 : 0.5 / (t1 - t0), k21 = t1 === t2 ? 0 : 0.5 / (t2 - t1), s = t1 < t0 ? -1 : 1, scale) : [x0, x1, x2];
  };

  scale.clamp = function(_) {
    return arguments.length ? (clamp = !!_, scale) : clamp;
  };

  scale.interpolator = function(_) {
    return arguments.length ? (interpolator = _, scale) : interpolator;
  };

  function range(interpolate) {
    return function(_) {
      var r0, r1, r2;
      return arguments.length ? ([r0, r1, r2] = _, interpolator = piecewise(interpolate, [r0, r1, r2]), scale) : [interpolator(0), interpolator(0.5), interpolator(1)];
    };
  }

  scale.range = range(interpolate$1);

  scale.rangeRound = range(interpolateRound);

  scale.unknown = function(_) {
    return arguments.length ? (unknown = _, scale) : unknown;
  };

  return function(t) {
    transform = t, t0 = t(x0), t1 = t(x1), t2 = t(x2), k10 = t0 === t1 ? 0 : 0.5 / (t1 - t0), k21 = t1 === t2 ? 0 : 0.5 / (t2 - t1), s = t1 < t0 ? -1 : 1;
    return scale;
  };
}

function diverging() {
  var scale = linearish(transformer$2()(identity$1));

  scale.copy = function() {
    return copy$1(scale, diverging());
  };

  return initInterpolator.apply(scale, arguments);
}

function divergingLog() {
  var scale = loggish(transformer$2()).domain([0.1, 1, 10]);

  scale.copy = function() {
    return copy$1(scale, divergingLog()).base(scale.base());
  };

  return initInterpolator.apply(scale, arguments);
}

function divergingSymlog() {
  var scale = symlogish(transformer$2());

  scale.copy = function() {
    return copy$1(scale, divergingSymlog()).constant(scale.constant());
  };

  return initInterpolator.apply(scale, arguments);
}

function divergingPow() {
  var scale = powish(transformer$2());

  scale.copy = function() {
    return copy$1(scale, divergingPow()).exponent(scale.exponent());
  };

  return initInterpolator.apply(scale, arguments);
}

function divergingSqrt() {
  return divergingPow.apply(null, arguments).exponent(0.5);
}

function band() {
  var scale = ordinal().unknown(undefined),
      domain = scale.domain,
      ordinalRange = scale.range,
      range = [0, 1],
      step,
      bandwidth,
      round = false,
      paddingInner = 0,
      paddingOuter = 0,
      align = 0.5;

  delete scale.unknown;

  function rescale() {
    var n = domain().length,
        reverse = range[1] < range[0],
        start = range[reverse - 0],
        stop = range[1 - reverse],
        space = bandSpace(n, paddingInner, paddingOuter);

    step = (stop - start) / (space || 1);
    if (round) {
      step = Math.floor(step);
    }
    start += (stop - start - step * (n - paddingInner)) * align;
    bandwidth = step * (1 - paddingInner);
    if (round) {
      start = Math.round(start);
      bandwidth = Math.round(bandwidth);
    }
    var values = sequence(n).map(function(i) { return start + step * i; });
    return ordinalRange(reverse ? values.reverse() : values);
  }

  scale.domain = function(_) {
    if (arguments.length) {
      domain(_);
      return rescale();
    } else {
      return domain();
    }
  };

  scale.range = function(_) {
    if (arguments.length) {
      range = [+_[0], +_[1]];
      return rescale();
    } else {
      return range.slice();
    }
  };

  scale.rangeRound = function(_) {
    range = [+_[0], +_[1]];
    round = true;
    return rescale();
  };

  scale.bandwidth = function() {
    return bandwidth;
  };

  scale.step = function() {
    return step;
  };

  scale.round = function(_) {
    if (arguments.length) {
      round = !!_;
      return rescale();
    } else {
      return round;
    }
  };

  scale.padding = function(_) {
    if (arguments.length) {
      paddingOuter = Math.max(0, Math.min(1, _));
      paddingInner = paddingOuter;
      return rescale();
    } else {
      return paddingInner;
    }
  };

  scale.paddingInner = function(_) {
    if (arguments.length) {
      paddingInner = Math.max(0, Math.min(1, _));
      return rescale();
    } else {
      return paddingInner;
    }
  };

  scale.paddingOuter = function(_) {
    if (arguments.length) {
      paddingOuter = Math.max(0, Math.min(1, _));
      return rescale();
    } else {
      return paddingOuter;
    }
  };

  scale.align = function(_) {
    if (arguments.length) {
      align = Math.max(0, Math.min(1, _));
      return rescale();
    } else {
      return align;
    }
  };

  scale.invertRange = function(_) {
    // bail if range has null or undefined values
    if (_[0] == null || _[1] == null) return;

    var lo = +_[0],
        hi = +_[1],
        reverse = range[1] < range[0],
        values = reverse ? ordinalRange().reverse() : ordinalRange(),
        n = values.length - 1, a, b, t;

    // bail if either range endpoint is invalid
    if (lo !== lo || hi !== hi) return;

    // order range inputs, bail if outside of scale range
    if (hi < lo) {
      t = lo;
      lo = hi;
      hi = t;
    }
    if (hi < values[0] || lo > range[1-reverse]) return;

    // binary search to index into scale range
    a = Math.max(0, bisectRight(values, lo) - 1);
    b = lo===hi ? a : bisectRight(values, hi) - 1;

    // increment index a if lo is within padding gap
    if (lo - values[a] > bandwidth + 1e-10) ++a;

    if (reverse) {
      // map + swap
      t = a;
      a = n - b;
      b = n - t;
    }
    return (a > b) ? undefined : domain().slice(a, b+1);
  };

  scale.invert = function(_) {
    var value = scale.invertRange([_, _]);
    return value ? value[0] : value;
  };

  scale.copy = function() {
    return band()
        .domain(domain())
        .range(range)
        .round(round)
        .paddingInner(paddingInner)
        .paddingOuter(paddingOuter)
        .align(align);
  };

  return rescale();
}

function pointish(scale) {
  var copy = scale.copy;

  scale.padding = scale.paddingOuter;
  delete scale.paddingInner;

  scale.copy = function() {
    return pointish(copy());
  };

  return scale;
}

function point$1() {
  return pointish(band().paddingInner(1));
}

var map = Array.prototype.map;

function numbers$2(_) {
  return map.call(_, function(x) { return +x; });
}

var slice = Array.prototype.slice;

function scaleBinOrdinal() {
  var domain = [],
      range = [];

  function scale(x) {
    return x == null || x !== x
      ? undefined
      : range[(bisectRight(domain, x) - 1) % range.length];
  }

  scale.domain = function(_) {
    if (arguments.length) {
      domain = numbers$2(_);
      return scale;
    } else {
      return domain.slice();
    }
  };

  scale.range = function(_) {
    if (arguments.length) {
      range = slice.call(_);
      return scale;
    } else {
      return range.slice();
    }
  };

  scale.tickFormat = function(count, specifier) {
    return spanFormat(domain[0], peek(domain), count == null ? 10 : count, specifier);
  };

  scale.copy = function() {
    return scaleBinOrdinal().domain(scale.domain()).range(scale.range());
  };

  return scale;
}

// scale registry
const scales = {};

/**
 * Augment scales with their type and needed inverse methods.
 */
function create(type, constructor, metadata) {
  const ctr = function scale() {
    var s = constructor();

    if (!s.invertRange) {
      s.invertRange = s.invert ? invertRange(s)
        : s.invertExtent ? invertRangeExtent(s)
        : undefined;
    }

    s.type = type;
    return s;
  };

  ctr.metadata = toSet(array(metadata));

  return ctr;
}

function scale$2(type, scale, metadata) {
  if (arguments.length > 1) {
    scales[type] = create(type, scale, metadata);
    return this;
  } else {
    return isValidScaleType(type) ? scales[type] : undefined;
  }
}

// identity scale
scale$2(Identity, identity$2);

// continuous scales
scale$2(Linear, linear, Continuous);
scale$2(Log, log$2, [Continuous, Log]);
scale$2(Pow, pow$1, Continuous);
scale$2(Sqrt, sqrt, Continuous);
scale$2(Symlog, symlog$1, Continuous);
scale$2(Time, time, [Continuous, Temporal]);
scale$2(UTC, utcTime, [Continuous, Temporal]);

// sequential scales
scale$2(Sequential, sequential, [Continuous, Interpolating]); // backwards compat
scale$2(`${Sequential}-${Linear}`, sequential, [Continuous, Interpolating]);
scale$2(`${Sequential}-${Log}`, sequentialLog, [Continuous, Interpolating, Log]);
scale$2(`${Sequential}-${Pow}`, sequentialPow, [Continuous, Interpolating]);
scale$2(`${Sequential}-${Sqrt}`, sequentialSqrt, [Continuous, Interpolating]);
scale$2(`${Sequential}-${Symlog}`, sequentialSymlog, [Continuous, Interpolating]);

// diverging scales
scale$2(`${Diverging}-${Linear}`, diverging, [Continuous, Interpolating]);
scale$2(`${Diverging}-${Log}`, divergingLog, [Continuous, Interpolating, Log]);
scale$2(`${Diverging}-${Pow}`, divergingPow, [Continuous, Interpolating]);
scale$2(`${Diverging}-${Sqrt}`, divergingSqrt, [Continuous, Interpolating]);
scale$2(`${Diverging}-${Symlog}`, divergingSymlog, [Continuous, Interpolating]);

// discretizing scales
scale$2(Quantile$1, quantile$1, [Discretizing, Quantile$1]);
scale$2(Quantize, quantize, Discretizing);
scale$2(Threshold, threshold, Discretizing);

// discrete scales
scale$2(BinOrdinal, scaleBinOrdinal, [Discrete, Discretizing]);
scale$2(Ordinal, ordinal, Discrete);
scale$2(Band, band, Discrete);
scale$2(Point, point$1, Discrete);

function isValidScaleType(type) {
  return hasOwnProperty(scales, type);
}

function hasType(key, type) {
  const s = scales[key];
  return s && s.metadata[type];
}

function isContinuous(key) {
  return hasType(key, Continuous);
}

function isDiscrete(key) {
  return hasType(key, Discrete);
}

function isDiscretizing(key) {
  return hasType(key, Discretizing);
}

function isLogarithmic(key) {
  return hasType(key, Log);
}

function isInterpolating(key) {
  return hasType(key, Interpolating);
}

function isQuantile(key) {
  return hasType(key, Quantile$1);
}

const scaleProps = ['clamp', 'base', 'constant', 'exponent'];

function interpolateRange(interpolator, range) {
  var start = range[0],
      span = peek(range) - start;
  return function(i) { return interpolator(start + i * span); };
}

function interpolateColors(colors, type, gamma) {
  return piecewise(interpolate(type || 'rgb', gamma), colors);
}

function quantizeInterpolator(interpolator, count) {
  var samples = new Array(count),
      n = count + 1;
  for (var i = 0; i < count;) samples[i] = interpolator(++i / n);
  return samples;
}

function scaleFraction(scale, min, max) {
  var delta = max - min, i, t, s;

  if (!delta || !Number.isFinite(delta)) {
    return constant(0.5);
  } else {
    i = (t = scale.type).indexOf('-');
    t = i < 0 ? t : t.slice(i + 1);
    s = scale$2(t)().domain([min, max]).range([0, 1]);
    scaleProps.forEach(m => scale[m] ? s[m](scale[m]()) : 0);
    return s;
  }
}

function interpolate(type, gamma) {
  var interp = $$1[method(type)];
  return (gamma != null && interp && interp.gamma)
    ? interp.gamma(gamma)
    : interp;
}

function method(type) {
  return 'interpolate' + type.toLowerCase()
    .split('-')
    .map(function(s) { return s[0].toUpperCase() + s.slice(1); })
    .join('');
}

const continuous$1 = {
  blues: 'cfe1f2bed8eca8cee58fc1de74b2d75ba3cf4592c63181bd206fb2125ca40a4a90',
  greens: 'd3eecdc0e6baabdda594d3917bc77d60ba6c46ab5e329a512089430e7735036429',
  greys: 'e2e2e2d4d4d4c4c4c4b1b1b19d9d9d8888887575756262624d4d4d3535351e1e1e',
  oranges: 'fdd8b3fdc998fdb87bfda55efc9244f87f2cf06b18e4580bd14904b93d029f3303',
  purples: 'e2e1efd4d4e8c4c5e0b4b3d6a3a0cc928ec3827cb97566ae684ea25c3696501f8c',
  reds: 'fdc9b4fcb49afc9e80fc8767fa7051f6573fec3f2fdc2a25c81b1db21218970b13',

  blueGreen: 'd5efedc1e8e0a7ddd18bd2be70c6a958ba9144ad77319c5d2089460e7736036429',
  bluePurple: 'ccddecbad0e4a8c2dd9ab0d4919cc98d85be8b6db28a55a6873c99822287730f71',
  greenBlue: 'd3eecec5e8c3b1e1bb9bd8bb82cec269c2ca51b2cd3c9fc7288abd1675b10b60a1',
  orangeRed: 'fddcaffdcf9bfdc18afdad77fb9562f67d53ee6545e24932d32d1ebf130da70403',
  purpleBlue: 'dbdaebc8cee4b1c3de97b7d87bacd15b9fc93a90c01e7fb70b70ab056199045281',
  purpleBlueGreen: 'dbd8eac8cee4b0c3de93b7d872acd1549fc83892bb1c88a3097f8702736b016353',
  purpleRed: 'dcc9e2d3b3d7ce9eccd186c0da6bb2e14da0e23189d91e6fc61159ab07498f023a',
  redPurple: 'fccfccfcbec0faa9b8f98faff571a5ec539ddb3695c41b8aa908808d0179700174',
  yellowGreen: 'e4f4acd1eca0b9e2949ed68880c97c62bb6e47aa5e3297502083440e723b036034',
  yellowOrangeBrown: 'feeaa1fedd84fecc63feb746fca031f68921eb7215db5e0bc54c05ab3d038f3204',
  yellowOrangeRed: 'fee087fed16ffebd59fea849fd903efc7335f9522bee3423de1b20ca0b22af0225',

  blueOrange: '134b852f78b35da2cb9dcae1d2e5eff2f0ebfce0bafbbf74e8932fc5690d994a07',
  brownBlueGreen: '704108a0651ac79548e3c78af3e6c6eef1eac9e9e48ed1c74da79e187a72025147',
  purpleGreen: '5b1667834792a67fb6c9aed3e6d6e8eff0efd9efd5aedda971bb75368e490e5e29',
  purpleOrange: '4114696647968f83b7b9b4d6dadbebf3eeeafce0bafbbf74e8932fc5690d994a07',
  redBlue: '8c0d25bf363adf745ef4ae91fbdbc9f2efeed2e5ef9dcae15da2cb2f78b3134b85',
  redGrey: '8c0d25bf363adf745ef4ae91fcdccbfaf4f1e2e2e2c0c0c0969696646464343434',
  yellowGreenBlue: 'eff9bddbf1b4bde5b594d5b969c5be45b4c22c9ec02182b82163aa23479c1c3185',
  redYellowBlue: 'a50026d4322cf16e43fcac64fedd90faf8c1dcf1ecabd6e875abd04a74b4313695',
  redYellowGreen: 'a50026d4322cf16e43fcac63fedd8df9f7aed7ee8ea4d86e64bc6122964f006837',
  pinkYellowGreen: '8e0152c0267edd72adf0b3d6faddedf5f3efe1f2cab6de8780bb474f9125276419',
  spectral: '9e0142d13c4bf0704afcac63fedd8dfbf8b0e0f3a1a9dda269bda94288b55e4fa2',

  viridis: '440154470e61481a6c482575472f7d443a834144873d4e8a39568c35608d31688e2d708e2a788e27818e23888e21918d1f988b1fa08822a8842ab07f35b77943bf7154c56866cc5d7ad1518fd744a5db36bcdf27d2e21be9e51afde725',
  magma: '0000040404130b0924150e3720114b2c11603b0f704a107957157e651a80721f817f24828c29819a2e80a8327db6377ac43c75d1426fde4968e95462f1605df76f5cfa7f5efc8f65fe9f6dfeaf78febf84fece91fddea0fcedaffcfdbf',
  inferno: '0000040403130c0826170c3b240c4f330a5f420a68500d6c5d126e6b176e781c6d86216b932667a12b62ae305cbb3755c73e4cd24644dd513ae65c30ed6925f3771af8850ffb9506fca50afcb519fac62df6d645f2e661f3f484fcffa4',
  plasma: '0d088723069033059742039d5002a25d01a66a00a87801a88405a7900da49c179ea72198b12a90ba3488c33d80cb4779d35171da5a69e16462e76e5bed7953f2834cf68f44fa9a3dfca636fdb32ffec029fcce25f9dc24f5ea27f0f921',

  rainbow: '6e40aa883eb1a43db3bf3cafd83fa4ee4395fe4b83ff576eff6659ff7847ff8c38f3a130e2b72fcfcc36bee044aff05b8ff4576ff65b52f6673af27828ea8d1ddfa319d0b81cbecb23abd82f96e03d82e14c6edb5a5dd0664dbf6e40aa',
  sinebow: 'ff4040fc582af47218e78d0bd5a703bfbf00a7d5038de70b72f41858fc2a40ff402afc5818f4720be78d03d5a700bfbf03a7d50b8de71872f42a58fc4040ff582afc7218f48d0be7a703d5bf00bfd503a7e70b8df41872fc2a58ff4040',

  browns: 'eedbbdecca96e9b97ae4a865dc9856d18954c7784cc0673fb85536ad44339f3632',
  tealBlues: 'bce4d89dd3d181c3cb65b3c245a2b9368fae347da0306a932c5985',
  teals: 'bbdfdfa2d4d58ac9c975bcbb61b0af4da5a43799982b8b8c1e7f7f127273006667',
  warmGreys: 'dcd4d0cec5c1c0b8b4b3aaa7a59c9998908c8b827f7e7673726866665c5a59504e',

  goldGreen: 'f4d166d5ca60b6c35c98bb597cb25760a6564b9c533f8f4f33834a257740146c36',
  goldOrange: 'f4d166f8be5cf8aa4cf5983bf3852aef701be2621fd65322c54923b142239e3a26',
  goldRed: 'f4d166f6be59f9aa51fc964ef6834bee734ae56249db5247cf4244c43141b71d3e',

  lightGreyRed: 'efe9e6e1dad7d5cbc8c8bdb9bbaea9cd967ddc7b43e15f19df4011dc000b',
  lightGreyTeal: 'e4eaead6dcddc8ced2b7c2c7a6b4bc64b0bf22a6c32295c11f85be1876bc',
  lightMulti: 'e0f1f2c4e9d0b0de9fd0e181f6e072f6c053f3993ef77440ef4a3c',
  lightOrange: 'f2e7daf7d5baf9c499fab184fa9c73f68967ef7860e8645bde515bd43d5b',
  lightTealBlue: 'e3e9e0c0dccf9aceca7abfc859afc0389fb9328dad2f7ca0276b95255988',

  darkBlue: '3232322d46681a5c930074af008cbf05a7ce25c0dd38daed50f3faffffff',
  darkGold: '3c3c3c584b37725e348c7631ae8b2bcfa424ecc31ef9de30fff184ffffff',
  darkGreen: '3a3a3a215748006f4d048942489e4276b340a6c63dd2d836ffeb2cffffaa',
  darkMulti: '3737371f5287197d8c29a86995ce3fffe800ffffff',
  darkRed: '3434347036339e3c38cc4037e75d1eec8620eeab29f0ce32ffeb2c'
};

const discrete = {
  category10: '1f77b4ff7f0e2ca02cd627289467bd8c564be377c27f7f7fbcbd2217becf',
  category20: '1f77b4aec7e8ff7f0effbb782ca02c98df8ad62728ff98969467bdc5b0d58c564bc49c94e377c2f7b6d27f7f7fc7c7c7bcbd22dbdb8d17becf9edae5',
  category20b: '393b795254a36b6ecf9c9ede6379398ca252b5cf6bcedb9c8c6d31bd9e39e7ba52e7cb94843c39ad494ad6616be7969c7b4173a55194ce6dbdde9ed6',
  category20c: '3182bd6baed69ecae1c6dbefe6550dfd8d3cfdae6bfdd0a231a35474c476a1d99bc7e9c0756bb19e9ac8bcbddcdadaeb636363969696bdbdbdd9d9d9',
  tableau10: '4c78a8f58518e4575672b7b254a24beeca3bb279a2ff9da69d755dbab0ac',
  tableau20: '4c78a89ecae9f58518ffbf7954a24b88d27ab79a20f2cf5b43989483bcb6e45756ff9d9879706ebab0acd67195fcbfd2b279a2d6a5c99e765fd8b5a5',
  accent: '7fc97fbeaed4fdc086ffff99386cb0f0027fbf5b17666666',
  dark2: '1b9e77d95f027570b3e7298a66a61ee6ab02a6761d666666',
  paired: 'a6cee31f78b4b2df8a33a02cfb9a99e31a1cfdbf6fff7f00cab2d66a3d9affff99b15928',
  pastel1: 'fbb4aeb3cde3ccebc5decbe4fed9a6ffffcce5d8bdfddaecf2f2f2',
  pastel2: 'b3e2cdfdcdaccbd5e8f4cae4e6f5c9fff2aef1e2cccccccc',
  set1: 'e41a1c377eb84daf4a984ea3ff7f00ffff33a65628f781bf999999',
  set2: '66c2a5fc8d628da0cbe78ac3a6d854ffd92fe5c494b3b3b3',
  set3: '8dd3c7ffffb3bebadafb807280b1d3fdb462b3de69fccde5d9d9d9bc80bdccebc5ffed6f'
};

function colors(palette) {
  var n = palette.length / 6 | 0, c = new Array(n), i = 0;
  while (i < n) c[i] = '#' + palette.slice(i * 6, ++i * 6);
  return c;
}

function apply(_, f) {
  for (let k in _) scheme(k, f(_[k]));
}

const schemes = {};
apply(discrete, colors);
apply(continuous$1, _ => interpolateColors(colors(_)));

function scheme(name, scheme) {
  name = name && name.toLowerCase();
  if (arguments.length > 1) {
    schemes[name] = scheme;
    return this;
  } else {
    return schemes[name];
  }
}

/**
 * Determine the tick count or interval function.
 * @param {Scale} scale - The scale for which to generate tick values.
 * @param {*} count - The desired tick count or interval specifier.
 * @param {number} minStep - The desired minimum step between tick values.
 * @return {*} - The tick count or interval function.
 */
function tickCount(scale, count, minStep) {
  var step;

  if (isNumber(count)) {
    if (scale.bins) {
      count = Math.max(count, scale.bins.length);
    }
    if (minStep != null) {
      count = Math.min(count, ~~(span(scale.domain()) / minStep) || 1);
    }
  }

  if (isObject(count)) {
    step = count.step;
    count = count.interval;
  }

  if (isString(count)) {
    count = scale.type === Time ? timeInterval(count)
      : scale.type == UTC ? utcInterval(count)
      : error('Only time and utc scales accept interval strings.');
    if (step) count = count.every(step);
  }

  return count;
}

/**
 * Filter a set of candidate tick values, ensuring that only tick values
 * that lie within the scale range are included.
 * @param {Scale} scale - The scale for which to generate tick values.
 * @param {Array<*>} ticks - The candidate tick values.
 * @param {*} count - The tick count or interval function.
 * @return {Array<*>} - The filtered tick values.
 */
function validTicks(scale, ticks, count) {
  var range = scale.range(),
      lo = Math.floor(range[0]),
      hi = Math.ceil(peek(range));

  if (lo > hi) {
    range = hi;
    hi = lo;
    lo = range;
  }

  ticks = ticks.filter(function(v) {
    v = scale(v);
    return lo <= v && v <= hi;
  });

  if (count > 0 && ticks.length > 1) {
    var endpoints = [ticks[0], peek(ticks)];
    while (ticks.length > count && ticks.length >= 3) {
      ticks = ticks.filter(function(_, i) { return !(i % 2); });
    }
    if (ticks.length < 3) {
      ticks = endpoints;
    }
  }

  return ticks;
}

/**
 * Generate tick values for the given scale and approximate tick count or
 * interval value. If the scale has a 'ticks' method, it will be used to
 * generate the ticks, with the count argument passed as a parameter. If the
 * scale lacks a 'ticks' method, the full scale domain will be returned.
 * @param {Scale} scale - The scale for which to generate tick values.
 * @param {*} [count] - The approximate number of desired ticks.
 * @return {Array<*>} - The generated tick values.
 */
function tickValues(scale, count) {
  return scale.bins ? validTicks(scale, scale.bins)
    : scale.ticks ? scale.ticks(count)
    : scale.domain();
}

/**
 * Generate a label format function for a scale. If the scale has a
 * 'tickFormat' method, it will be used to generate the formatter, with the
 * count and specifier arguments passed as parameters. If the scale lacks a
 * 'tickFormat' method, the returned formatter performs simple string coercion.
 * If the input scale is a logarithmic scale and the format specifier does not
 * indicate a desired decimal precision, a special variable precision formatter
 * that automatically trims trailing zeroes will be generated.
 * @param {Scale} scale - The scale for which to generate the label formatter.
 * @param {*} [count] - The approximate number of desired ticks.
 * @param {string} [specifier] - The format specifier. Must be a legal d3
 *   specifier string (see https://github.com/d3/d3-format#formatSpecifier) or
 *   time multi-format specifier object.
 * @return {function(*):string} - The generated label formatter.
 */
function tickFormat(scale, count, specifier, formatType, noSkip) {
  var type = scale.type,
      format = (type === Time || formatType === Time) ? timeFormat(specifier)
        : (type === UTC || formatType === UTC) ? utcFormat(specifier)
        : scale.tickFormat ? scale.tickFormat(count, specifier)
        : specifier ? format$2(specifier)
        : String;

  if (isLogarithmic(type)) {
    var logfmt = variablePrecision(specifier);
    format = noSkip || scale.bins ? logfmt : filter$1(format, logfmt);
  }

  return format;
}

function filter$1(sourceFormat, targetFormat) {
  return _ => sourceFormat(_) ? targetFormat(_) : '';
}

function variablePrecision(specifier) {
  var s = formatSpecifier(specifier || ',');

  if (s.precision == null) {
    s.precision = 12;
    switch (s.type) {
      case '%': s.precision -= 2; break;
      case 'e': s.precision -= 1; break;
    }
    return trimZeroes(
      format$2(s),          // number format
      format$2('.1f')(1)[1] // decimal point character
    );
  } else {
    return format$2(s);
  }
}

function trimZeroes(format, decimalChar) {
  return function(x) {
    var str = format(x),
        dec = str.indexOf(decimalChar),
        idx, end;

    if (dec < 0) return str;

    idx = rightmostDigit(str, dec);
    end = idx < str.length ? str.slice(idx) : '';
    while (--idx > dec) if (str[idx] !== '0') { ++idx; break; }

    return str.slice(0, idx) + end;
  };
}

function rightmostDigit(str, dec) {
  var i = str.lastIndexOf('e'), c;
  if (i > 0) return i;
  for (i=str.length; --i > dec;) {
    c = str.charCodeAt(i);
    if (c >= 48 && c <= 57) return i + 1; // is digit
  }
}

/**
 * Generates axis ticks for visualizing a spatial scale.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Scale} params.scale - The scale to generate ticks for.
 * @param {*} [params.count=10] - The approximate number of ticks, or
 *   desired tick interval, to use.
 * @param {Array<*>} [params.values] - The exact tick values to use.
 *   These must be legal domain values for the provided scale.
 *   If provided, the count argument is ignored.
 * @param {function(*):string} [params.formatSpecifier] - A format specifier
 *   to use in conjunction with scale.tickFormat. Legal values are
 *   any valid d3 4.0 format specifier.
 * @param {function(*):string} [params.format] - The format function to use.
 *   If provided, the formatSpecifier argument is ignored.
 */
function AxisTicks(params) {
  Transform.call(this, null, params);
}

var prototype$W = inherits(AxisTicks, Transform);

prototype$W.transform = function(_, pulse) {
  if (this.value && !_.modified()) {
    return pulse.StopPropagation;
  }

  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS),
      ticks = this.value,
      scale = _.scale,
      tally = _.count == null ? (_.values ? _.values.length : 10) : _.count,
      count = tickCount(scale, tally, _.minstep),
      format = _.format || tickFormat(scale, count, _.formatSpecifier, _.formatType, !!_.values),
      values = _.values ? validTicks(scale, _.values, count) : tickValues(scale, count);

  if (ticks) out.rem = ticks;

  ticks = values.map(function(value, i) {
    return ingest({
      index: i / (values.length - 1 || 1),
      value: value,
      label: format(value)
    });
  });

  if (_.extra && ticks.length) {
    // add an extra tick pegged to the initial domain value
    // this is used to generate axes with 'binned' domains
    ticks.push(ingest({
      index: -1,
      extra: {value: ticks[0].value},
      label: ''
    }));
  }

  out.source = ticks;
  out.add = ticks;
  this.value = ticks;

  return out;
};

/**
 * Joins a set of data elements against a set of visual items.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): object} [params.item] - An item generator function.
 * @param {function(object): *} [params.key] - The key field associating data and visual items.
 */
function DataJoin(params) {
  Transform.call(this, null, params);
}

var prototype$X = inherits(DataJoin, Transform);

function defaultItemCreate() {
  return ingest({});
}

function isExit(t) {
  return t.exit;
}

prototype$X.transform = function(_, pulse) {
  var df = pulse.dataflow,
      out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS),
      item = _.item || defaultItemCreate,
      key = _.key || tupleid,
      map = this.value;

  // prevent transient (e.g., hover) requests from
  // cascading across marks derived from marks
  if (isArray(out.encode)) {
    out.encode = null;
  }

  if (map && (_.modified('key') || pulse.modified(key))) {
    error('DataJoin does not support modified key function or fields.');
  }

  if (!map) {
    pulse = pulse.addAll();
    this.value = map = fastmap().test(isExit);
    map.lookup = function(t) { return map.get(key(t)); };
  }

  pulse.visit(pulse.ADD, function(t) {
    var k = key(t),
        x = map.get(k);

    if (x) {
      if (x.exit) {
        map.empty--;
        out.add.push(x);
      } else {
        out.mod.push(x);
      }
    } else {
      map.set(k, (x = item(t)));
      out.add.push(x);
    }

    x.datum = t;
    x.exit = false;
  });

  pulse.visit(pulse.MOD, function(t) {
    var k = key(t),
        x = map.get(k);

    if (x) {
      x.datum = t;
      out.mod.push(x);
    }
  });

  pulse.visit(pulse.REM, function(t) {
    var k = key(t),
        x = map.get(k);

    if (t === x.datum && !x.exit) {
      out.rem.push(x);
      x.exit = true;
      ++map.empty;
    }
  });

  if (pulse.changed(pulse.ADD_MOD)) out.modifies('datum');

  if (_.clean && map.empty > df.cleanThreshold) df.runAfter(map.clean);

  return out;
};

/**
 * Invokes encoding functions for visual items.
 * @constructor
 * @param {object} params - The parameters to the encoding functions. This
 *   parameter object will be passed through to all invoked encoding functions.
 * @param {object} [params.mod=false] - Flag indicating if tuples in the input
 *   mod set that are unmodified by encoders should be included in the output.
 * @param {object} param.encoders - The encoding functions
 * @param {function(object, object): boolean} [param.encoders.update] - Update encoding set
 * @param {function(object, object): boolean} [param.encoders.enter] - Enter encoding set
 * @param {function(object, object): boolean} [param.encoders.exit] - Exit encoding set
 */
function Encode(params) {
  Transform.call(this, null, params);
}

var prototype$Y = inherits(Encode, Transform);

prototype$Y.transform = function(_, pulse) {
  var out = pulse.fork(pulse.ADD_REM),
      fmod = _.mod || false,
      encoders = _.encoders,
      encode = pulse.encode;

  // if an array, the encode directive includes additional sets
  // that must be defined in order for the primary set to be invoked
  // e.g., only run the update set if the hover set is defined
  if (isArray(encode)) {
    if (out.changed() || encode.every(function(e) { return encoders[e]; })) {
      encode = encode[0];
      out.encode = null; // consume targeted encode directive
    } else {
      return pulse.StopPropagation;
    }
  }

  // marshall encoder functions
  var reenter = encode === 'enter',
      update = encoders.update || falsy,
      enter = encoders.enter || falsy,
      exit = encoders.exit || falsy,
      set = (encode && !reenter ? encoders[encode] : update) || falsy;

  if (pulse.changed(pulse.ADD)) {
    pulse.visit(pulse.ADD, function(t) { enter(t, _); update(t, _); });
    out.modifies(enter.output);
    out.modifies(update.output);
    if (set !== falsy && set !== update) {
      pulse.visit(pulse.ADD, function(t) { set(t, _); });
      out.modifies(set.output);
    }
  }

  if (pulse.changed(pulse.REM) && exit !== falsy) {
    pulse.visit(pulse.REM, function(t) { exit(t, _); });
    out.modifies(exit.output);
  }

  if (reenter || set !== falsy) {
    var flag = pulse.MOD | (_.modified() ? pulse.REFLOW : 0);
    if (reenter) {
      pulse.visit(flag, function(t) {
        var mod = enter(t, _) || fmod;
        if (set(t, _) || mod) out.mod.push(t);
      });
      if (out.mod.length) out.modifies(enter.output);
    } else {
      pulse.visit(flag, function(t) {
        if (set(t, _) || fmod) out.mod.push(t);
      });
    }
    if (out.mod.length) out.modifies(set.output);
  }

  return out.changed() ? out : pulse.StopPropagation;
};

var Symbols$1  = 'symbol';
var Discrete$1 = 'discrete';
var Gradient$1 = 'gradient';

const symbols$1 = {
  [Quantile$1]:  'quantiles',
  [Quantize]:  'thresholds',
  [Threshold]: 'domain'
};

const formats$1 = {
  [Quantile$1]:  'quantiles',
  [Quantize]:  'domain'
};

function labelValues(scale, count) {
  return scale.bins ? binValues(scale.bins)
    : scale.type === Log ? logValues(scale, count)
    : symbols$1[scale.type] ? thresholdValues(scale[symbols$1[scale.type]]())
    : tickValues(scale, count);
}

function logValues(scale, count) {
  var ticks = tickValues(scale, count),
      base = scale.base(),
      logb = Math.log(base),
      k = Math.max(1, base * count / ticks.length);

  // apply d3-scale's log format filter criteria
  return ticks.filter(d => {
    var i = d / Math.pow(base, Math.round(Math.log(d) / logb));
    if (i * base < base - 0.5) i *= base;
    return i <= k;
  });
}

function thresholdFormat(scale, specifier) {
  var _ = scale[formats$1[scale.type]](),
      n = _.length,
      d = n > 1 ? _[1] - _[0] : _[0], i;

  for (i=1; i<n; ++i) {
    d = Math.min(d, _[i] - _[i-1]);
  }

  // 3 ticks times 10 for increased resolution
  return spanFormat(0, d, 3 * 10, specifier);
}

function thresholdValues(thresholds) {
  const values = [-Infinity].concat(thresholds);
  values.max = +Infinity;

  return values;
}

function binValues(bins) {
  const values = bins.slice(0, -1);
  values.max = peek(bins);

  return values;
}

function isDiscreteRange(scale) {
  return symbols$1[scale.type] || scale.bins;
}

function labelFormat(scale, count, type, specifier, formatType, noSkip) {
  const format = formats$1[scale.type] && formatType !== Time && formatType !== UTC
    ? thresholdFormat(scale, specifier)
    : tickFormat(scale, count, specifier, formatType, noSkip);

  return type === Symbols$1 && isDiscreteRange(scale) ? formatRange(format)
    : type === Discrete$1 ? formatDiscrete(format)
    : formatPoint(format);
}

function formatRange(format) {
  return function(value, index, array) {
    var limit = get$3(array[index + 1], get$3(array.max, +Infinity)),
        lo = formatValue(value, format),
        hi = formatValue(limit, format);
    return lo && hi ? lo + ' \u2013 ' + hi : hi ? '< ' + hi : '\u2265 ' + lo;
  };
}

function get$3(value, dflt) {
  return value != null ? value : dflt;
}

function formatDiscrete(format) {
  return function(value, index) {
    return index ? format(value) : null;
  }
}

function formatPoint(format) {
  return function(value) {
    return format(value);
  };
}

function formatValue(value, format) {
  return Number.isFinite(value) ? format(value) : null;
}

function labelFraction(scale) {
  var domain = scale.domain(),
      count = domain.length - 1,
      lo = +domain[0],
      hi = +peek(domain),
      span = hi - lo;

  if (scale.type === Threshold) {
    var adjust = count ? span / count : 0.1;
    lo -= adjust;
    hi += adjust;
    span = hi - lo;
  }

  return function(value) {
    return (value - lo) / span;
  };
}

/**
 * Generates legend entries for visualizing a scale.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Scale} params.scale - The scale to generate items for.
 * @param {*} [params.count=5] - The approximate number of items, or
 *   desired tick interval, to use.
 * @param {*} [params.limit] - The maximum number of entries to
 *   include in a symbol legend.
 * @param {Array<*>} [params.values] - The exact tick values to use.
 *   These must be legal domain values for the provided scale.
 *   If provided, the count argument is ignored.
 * @param {string} [params.formatSpecifier] - A format specifier
 *   to use in conjunction with scale.tickFormat. Legal values are
 *   any valid D3 format specifier string.
 * @param {function(*):string} [params.format] - The format function to use.
 *   If provided, the formatSpecifier argument is ignored.
 */
function LegendEntries(params) {
  Transform.call(this, [], params);
}

var prototype$Z = inherits(LegendEntries, Transform);

prototype$Z.transform = function(_, pulse) {
  if (this.value != null && !_.modified()) {
    return pulse.StopPropagation;
  }

  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS),
      items = this.value,
      type  = _.type || Symbols$1,
      scale = _.scale,
      limit = +_.limit,
      count = tickCount(scale, _.count == null ? 5 : _.count, _.minstep),
      lskip = !!_.values || type === Symbols$1,
      format = _.format || labelFormat(scale, count, type, _.formatSpecifier, _.formatType, lskip),
      values = _.values || labelValues(scale, count),
      domain, fraction, size, offset, ellipsis;

  if (items) out.rem = items;

  if (type === Symbols$1) {
    if (limit && values.length > limit) {
      pulse.dataflow.warn('Symbol legend count exceeds limit, filtering items.');
      items = values.slice(0, limit - 1);
      ellipsis = true;
    } else {
      items = values;
    }

    if (isFunction(size = _.size)) {
      // if first value maps to size zero, remove from list (vega#717)
      if (!_.values && scale(items[0]) === 0) {
        items = items.slice(1);
      }
      // compute size offset for legend entries
      offset = items.reduce(function(max, value) {
        return Math.max(max, size(value, _));
      }, 0);
    } else {
      size = constant(offset = size || 8);
    }

    items = items.map(function(value, index) {
      return ingest({
        index:  index,
        label:  format(value, index, items),
        value:  value,
        offset: offset,
        size:   size(value, _)
      });
    });

    if (ellipsis) {
      ellipsis = values[items.length];
      items.push(ingest({
        index:    items.length,
        label:    `\u2026${values.length-items.length} entries`,
        value:    ellipsis,
        offset:   offset,
        size:     size(ellipsis, _)
      }));
    }
  }

  else if (type === Gradient$1) {
    domain = scale.domain(),
    fraction = scaleFraction(scale, domain[0], peek(domain));

    // if automatic label generation produces 2 or fewer values,
    // use the domain end points instead (fixes vega/vega#1364)
    if (values.length < 3 && !_.values && domain[0] !== peek(domain)) {
      values = [domain[0], peek(domain)];
    }

    items = values.map(function(value, index) {
      return ingest({
        index: index,
        label: format(value, index, values),
        value: value,
        perc:  fraction(value)
      });
    });
  }

  else {
    size = values.length - 1;
    fraction = labelFraction(scale);

    items = values.map(function(value, index) {
      return ingest({
        index: index,
        label: format(value, index, values),
        value: value,
        perc:  index ? fraction(value) : 0,
        perc2: index === size ? 1 : fraction(values[index+1])
      });
    });
  }

  out.source = items;
  out.add = items;
  this.value = items;

  return out;
};

var Paths = fastmap({
  'line': line$2,
  'line-radial': lineR,
  'arc': arc$2,
  'arc-radial': arcR,
  'curve': curve,
  'curve-radial': curveR,
  'orthogonal-horizontal': orthoX,
  'orthogonal-vertical': orthoY,
  'orthogonal-radial': orthoR,
  'diagonal-horizontal': diagonalX,
  'diagonal-vertical': diagonalY,
  'diagonal-radial': diagonalR
});

function sourceX(t) { return t.source.x; }
function sourceY(t) { return t.source.y; }
function targetX(t) { return t.target.x; }
function targetY(t) { return t.target.y; }

 /**
  * Layout paths linking source and target elements.
  * @constructor
  * @param {object} params - The parameters for this operator.
  */
function LinkPath(params) {
  Transform.call(this, {}, params);
}

LinkPath.Definition = {
  "type": "LinkPath",
  "metadata": {"modifies": true},
  "params": [
    { "name": "sourceX", "type": "field", "default": "source.x" },
    { "name": "sourceY", "type": "field", "default": "source.y" },
    { "name": "targetX", "type": "field", "default": "target.x" },
    { "name": "targetY", "type": "field", "default": "target.y" },
    { "name": "orient", "type": "enum", "default": "vertical",
      "values": ["horizontal", "vertical", "radial"] },
    { "name": "shape", "type": "enum", "default": "line",
      "values": ["line", "arc", "curve", "diagonal", "orthogonal"] },
    { "name": "require", "type": "signal" },
    { "name": "as", "type": "string", "default": "path" }
  ]
};

var prototype$_ = inherits(LinkPath, Transform);

prototype$_.transform = function(_, pulse) {
  var sx = _.sourceX || sourceX,
      sy = _.sourceY || sourceY,
      tx = _.targetX || targetX,
      ty = _.targetY || targetY,
      as = _.as || 'path',
      orient = _.orient || 'vertical',
      shape = _.shape || 'line',
      path = Paths.get(shape + '-' + orient) || Paths.get(shape);

  if (!path) {
    error('LinkPath unsupported type: ' + _.shape
      + (_.orient ? '-' + _.orient : ''));
  }

  pulse.visit(pulse.SOURCE, function(t) {
    t[as] = path(sx(t), sy(t), tx(t), ty(t));
  });

  return pulse.reflow(_.modified()).modifies(as);
};

// -- Link Path Generation Methods -----

function line$2(sx, sy, tx, ty) {
  return 'M' + sx + ',' + sy +
         'L' + tx + ',' + ty;
}

function lineR(sa, sr, ta, tr) {
  return line$2(
    sr * Math.cos(sa), sr * Math.sin(sa),
    tr * Math.cos(ta), tr * Math.sin(ta)
  );
}

function arc$2(sx, sy, tx, ty) {
  var dx = tx - sx,
      dy = ty - sy,
      rr = Math.sqrt(dx * dx + dy * dy) / 2,
      ra = 180 * Math.atan2(dy, dx) / Math.PI;
  return 'M' + sx + ',' + sy +
         'A' + rr + ',' + rr +
         ' ' + ra + ' 0 1' +
         ' ' + tx + ',' + ty;
}

function arcR(sa, sr, ta, tr) {
  return arc$2(
    sr * Math.cos(sa), sr * Math.sin(sa),
    tr * Math.cos(ta), tr * Math.sin(ta)
  );
}

function curve(sx, sy, tx, ty) {
  var dx = tx - sx,
      dy = ty - sy,
      ix = 0.2 * (dx + dy),
      iy = 0.2 * (dy - dx);
  return 'M' + sx + ',' + sy +
         'C' + (sx+ix) + ',' + (sy+iy) +
         ' ' + (tx+iy) + ',' + (ty-ix) +
         ' ' + tx + ',' + ty;
}

function curveR(sa, sr, ta, tr) {
  return curve(
    sr * Math.cos(sa), sr * Math.sin(sa),
    tr * Math.cos(ta), tr * Math.sin(ta)
  );
}

function orthoX(sx, sy, tx, ty) {
  return 'M' + sx + ',' + sy +
         'V' + ty + 'H' + tx;
}

function orthoY(sx, sy, tx, ty) {
  return 'M' + sx + ',' + sy +
         'H' + tx + 'V' + ty;
}

function orthoR(sa, sr, ta, tr) {
  var sc = Math.cos(sa),
      ss = Math.sin(sa),
      tc = Math.cos(ta),
      ts = Math.sin(ta),
      sf = Math.abs(ta - sa) > Math.PI ? ta <= sa : ta > sa;
  return 'M' + (sr*sc) + ',' + (sr*ss) +
         'A' + sr + ',' + sr + ' 0 0,' + (sf?1:0) +
         ' ' + (sr*tc) + ',' + (sr*ts) +
         'L' + (tr*tc) + ',' + (tr*ts);
}

function diagonalX(sx, sy, tx, ty) {
  var m = (sx + tx) / 2;
  return 'M' + sx + ',' + sy +
         'C' + m  + ',' + sy +
         ' ' + m  + ',' + ty +
         ' ' + tx + ',' + ty;
}

function diagonalY(sx, sy, tx, ty) {
  var m = (sy + ty) / 2;
  return 'M' + sx + ',' + sy +
         'C' + sx + ',' + m +
         ' ' + tx + ',' + m +
         ' ' + tx + ',' + ty;
}

function diagonalR(sa, sr, ta, tr) {
  var sc = Math.cos(sa),
      ss = Math.sin(sa),
      tc = Math.cos(ta),
      ts = Math.sin(ta),
      mr = (sr + tr) / 2;
  return 'M' + (sr*sc) + ',' + (sr*ss) +
         'C' + (mr*sc) + ',' + (mr*ss) +
         ' ' + (mr*tc) + ',' + (mr*ts) +
         ' ' + (tr*tc) + ',' + (tr*ts);
}

/**
 * Pie and donut chart layout.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The value field to size pie segments.
 * @param {number} [params.startAngle=0] - The start angle (in radians) of the layout.
 * @param {number} [params.endAngle=2π] - The end angle (in radians) of the layout.
 * @param {boolean} [params.sort] - Boolean flag for sorting sectors by value.
 */
function Pie(params) {
  Transform.call(this, null, params);
}

Pie.Definition = {
  "type": "Pie",
  "metadata": {"modifies": true},
  "params": [
    { "name": "field", "type": "field" },
    { "name": "startAngle", "type": "number", "default": 0 },
    { "name": "endAngle", "type": "number", "default": 6.283185307179586 },
    { "name": "sort", "type": "boolean", "default": false },
    { "name": "as", "type": "string", "array": true, "length": 2, "default": ["startAngle", "endAngle"] }
  ]
};

var prototype$$ = inherits(Pie, Transform);

prototype$$.transform = function(_, pulse) {
  var as = _.as || ['startAngle', 'endAngle'],
      startAngle = as[0],
      endAngle = as[1],
      field = _.field || one,
      start = _.startAngle || 0,
      stop = _.endAngle != null ? _.endAngle : 2 * Math.PI,
      data = pulse.source,
      values = data.map(field),
      n = values.length,
      a = start,
      k = (stop - start) / sum(values),
      index = sequence(n),
      i, t, v;

  if (_.sort) {
    index.sort(function(a, b) {
      return values[a] - values[b];
    });
  }

  for (i=0; i<n; ++i) {
    v = values[index[i]];
    t = data[index[i]];
    t[startAngle] = a;
    t[endAngle] = (a += v * k);
  }

  this.value = values;
  return pulse.reflow(_.modified()).modifies(as);
};

var DEFAULT_COUNT = 5;

function includeZero(scale) {
  const type = scale.type;
  return !scale.bins && (
    type === Linear || type === Pow || type === Sqrt
  );
}

function includePad(type) {
  return isContinuous(type) && type !== Sequential;
}

var SKIP$2 = toSet([
  'set', 'modified', 'clear', 'type', 'scheme', 'schemeExtent', 'schemeCount',
  'domain', 'domainMin', 'domainMid', 'domainMax',
  'domainRaw', 'domainImplicit', 'nice', 'zero', 'bins',
  'range', 'rangeStep', 'round', 'reverse', 'interpolate', 'interpolateGamma'
]);

/**
 * Maintains a scale function mapping data values to visual channels.
 * @constructor
 * @param {object} params - The parameters for this operator.
 */
function Scale(params) {
  Transform.call(this, null, params);
  this.modified(true); // always treat as modified
}

var prototype$10 = inherits(Scale, Transform);

prototype$10.transform = function(_, pulse) {
  var df = pulse.dataflow,
      scale = this.value,
      key = scaleKey(_);

  if (!scale || key !== scale.type) {
    this.value = scale = scale$2(key)();
  }

  for (key in _) if (!SKIP$2[key]) {
    // padding is a scale property for band/point but not others
    if (key === 'padding' && includePad(scale.type)) continue;
    // invoke scale property setter, raise warning if not found
    isFunction(scale[key])
      ? scale[key](_[key])
      : df.warn('Unsupported scale property: ' + key);
  }

  configureRange(scale, _,
    configureBins(scale, _, configureDomain(scale, _, df))
  );

  return pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS);
};

function scaleKey(_) {
  var t = _.type, d = '', n;

  // backwards compatibility pre Vega 5.
  if (t === Sequential) return Sequential + '-' + Linear;

  if (isContinuousColor(_)) {
    n = _.rawDomain ? _.rawDomain.length
      : _.domain ? _.domain.length + +(_.domainMid != null)
      : 0;
    d = n === 2 ? Sequential + '-'
      : n === 3 ? Diverging + '-'
      : '';
  }

  return ((d + t) || Linear).toLowerCase();
}

function isContinuousColor(_) {
  const t = _.type;
  return isContinuous(t) && t !== Time && t !== UTC && (
    _.scheme || _.range && _.range.length && _.range.every(isString)
  );
}

function configureDomain(scale, _, df) {
  // check raw domain, if provided use that and exit early
  var raw = rawDomain(scale, _.domainRaw, df);
  if (raw > -1) return raw;

  var domain = _.domain,
      type = scale.type,
      zero = _.zero || (_.zero === undefined && includeZero(scale)),
      n, mid;

  if (!domain) return 0;

  // adjust continuous domain for minimum pixel padding
  if (includePad(type) && _.padding && domain[0] !== peek(domain)) {
    domain = padDomain(type, domain, _.range, _.padding, _.exponent, _.constant);
  }

  // adjust domain based on zero, min, max settings
  if (zero || _.domainMin != null || _.domainMax != null || _.domainMid != null) {
    n = ((domain = domain.slice()).length - 1) || 1;
    if (zero) {
      if (domain[0] > 0) domain[0] = 0;
      if (domain[n] < 0) domain[n] = 0;
    }
    if (_.domainMin != null) domain[0] = _.domainMin;
    if (_.domainMax != null) domain[n] = _.domainMax;

    if (_.domainMid != null) {
      mid = _.domainMid;
      if (mid < domain[0] || mid > domain[n]) {
        df.warn('Scale domainMid exceeds domain min or max.', mid);
      }
      domain.splice(n, 0, mid);
    }
  }

  // set the scale domain
  scale.domain(domainCheck(type, domain, df));

  // if ordinal scale domain is defined, prevent implicit
  // domain construction as side-effect of scale lookup
  if (type === Ordinal) {
    scale.unknown(_.domainImplicit ? implicit : undefined);
  }

  // perform 'nice' adjustment as requested
  if (_.nice && scale.nice) {
    scale.nice((_.nice !== true && tickCount(scale, _.nice)) || null);
  }

  // return the cardinality of the domain
  return domain.length;
}

function rawDomain(scale, raw, df) {
  if (raw) {
    scale.domain(domainCheck(scale.type, raw, df));
    return raw.length;
  } else {
    return -1;
  }
}

function padDomain(type, domain, range, pad, exponent, constant) {
  var span = Math.abs(peek(range) - range[0]),
      frac = span / (span - 2 * pad),
      d = type === Log    ? zoomLog(domain, null, frac)
        : type === Sqrt   ? zoomPow(domain, null, frac, 0.5)
        : type === Pow    ? zoomPow(domain, null, frac, exponent || 1)
        : type === Symlog ? zoomSymlog(domain, null, frac, constant || 1)
        : zoomLinear(domain, null, frac);

  domain = domain.slice();
  domain[0] = d[0];
  domain[domain.length-1] = d[1];
  return domain;
}

function domainCheck(type, domain, df) {
  if (isLogarithmic(type)) {
    // sum signs of domain values
    // if all pos or all neg, abs(sum) === domain.length
    var s = Math.abs(domain.reduce(function(s, v) {
      return s + (v < 0 ? -1 : v > 0 ? 1 : 0);
    }, 0));

    if (s !== domain.length) {
      df.warn('Log scale domain includes zero: ' + $(domain));
    }
  }
  return domain;
}

function configureBins(scale, _, count) {
  let bins = _.bins;

  if (bins && !isArray(bins)) {
    // generate bin boundary array
    let domain = scale.domain(),
        lo = domain[0],
        hi = peek(domain),
        start = bins.start == null ? lo : bins.start,
        stop = bins.stop == null ? hi : bins.stop,
        step = bins.step;

    if (!step) error('Scale bins parameter missing step property.');
    if (start < lo) start = step * Math.ceil(lo / step);
    if (stop > hi) stop = step * Math.floor(hi / step);
    bins = sequence(start, stop + step / 2, step);
  }

  if (bins) {
    // assign bin boundaries to scale instance
    scale.bins = bins;
  } else if (scale.bins) {
    // no current bins, remove bins if previously set
    delete scale.bins;
  }

  // special handling for bin-ordinal scales
  if (scale.type === BinOrdinal) {
    if (!bins) {
      // the domain specifies the bins
      scale.bins = scale.domain();
    } else if (!_.domain && !_.domainRaw) {
      // the bins specify the domain
      scale.domain(bins);
      count = bins.length;
    }
  }

  // return domain cardinality
  return count;
}

function configureRange(scale, _, count) {
  var type = scale.type,
      round = _.round || false,
      range = _.range;

  // if range step specified, calculate full range extent
  if (_.rangeStep != null) {
    range = configureRangeStep(type, _, count);
  }

  // else if a range scheme is defined, use that
  else if (_.scheme) {
    range = configureScheme(type, _, count);
    if (isFunction(range)) {
      if (scale.interpolator) {
        return scale.interpolator(range);
      } else {
        error(`Scale type ${type} does not support interpolating color schemes.`);
      }
    }
  }

  // given a range array for an interpolating scale, convert to interpolator
  if (range && isInterpolating(type)) {
    return scale.interpolator(
      interpolateColors(flip(range, _.reverse), _.interpolate, _.interpolateGamma)
    );
  }

  // configure rounding / interpolation
  if (range && _.interpolate && scale.interpolate) {
    scale.interpolate(interpolate(_.interpolate, _.interpolateGamma));
  } else if (isFunction(scale.round)) {
    scale.round(round);
  } else if (isFunction(scale.rangeRound)) {
    scale.interpolate(round ? interpolateRound : interpolate$1);
  }

  if (range) scale.range(flip(range, _.reverse));
}

function configureRangeStep(type, _, count) {
  if (type !== Band && type !== Point) {
    error('Only band and point scales support rangeStep.');
  }

  // calculate full range based on requested step size and padding
  var outer = (_.paddingOuter != null ? _.paddingOuter : _.padding) || 0,
      inner = type === Point ? 1
            : ((_.paddingInner != null ? _.paddingInner : _.padding) || 0);
  return [0, _.rangeStep * bandSpace(count, inner, outer)];
}

function configureScheme(type, _, count) {
  var extent = _.schemeExtent,
      name, scheme$1;

  if (isArray(_.scheme)) {
    scheme$1 = interpolateColors(_.scheme, _.interpolate, _.interpolateGamma);
  } else {
    name = _.scheme.toLowerCase();
    scheme$1 = scheme(name);
    if (!scheme$1) error(`Unrecognized scheme name: ${_.scheme}`);
  }

  // determine size for potential discrete range
  count = (type === Threshold) ? count + 1
    : (type === BinOrdinal) ? count - 1
    : (type === Quantile$1 || type === Quantize) ? (+_.schemeCount || DEFAULT_COUNT)
    : count;

  // adjust and/or quantize scheme as appropriate
  return isInterpolating(type) ? adjustScheme(scheme$1, extent, _.reverse)
    : isFunction(scheme$1) ? quantizeInterpolator(adjustScheme(scheme$1, extent), count)
    : type === Ordinal ? scheme$1 : scheme$1.slice(0, count);
}

function adjustScheme(scheme, extent, reverse) {
  return (isFunction(scheme) && (extent || reverse))
    ? interpolateRange(scheme, flip(extent || [0, 1], reverse))
    : scheme;
}

function flip(array, reverse) {
  return reverse ? array.slice().reverse() : array;
}

/**
 * Sorts scenegraph items in the pulse source array.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(*,*): number} [params.sort] - A comparator
 *   function for sorting tuples.
 */
function SortItems(params) {
  Transform.call(this, null, params);
}

var prototype$11 = inherits(SortItems, Transform);

prototype$11.transform = function(_, pulse) {
  var mod = _.modified('sort')
         || pulse.changed(pulse.ADD)
         || pulse.modified(_.sort.fields)
         || pulse.modified('datum');

  if (mod) pulse.source.sort(stableCompare(_.sort));

  this.modified(mod);
  return pulse;
};

var Zero = 'zero',
    Center = 'center',
    Normalize = 'normalize',
    DefOutput = ['y0', 'y1'];

/**
 * Stack layout for visualization elements.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The value field to stack.
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors to groupby.
 * @param {function(object,object): number} [params.sort] - A comparator for stack sorting.
 * @param {string} [offset='zero'] - Stack baseline offset. One of 'zero', 'center', 'normalize'.
 */
function Stack(params) {
  Transform.call(this, null, params);
}

Stack.Definition = {
  "type": "Stack",
  "metadata": {"modifies": true},
  "params": [
    { "name": "field", "type": "field" },
    { "name": "groupby", "type": "field", "array": true },
    { "name": "sort", "type": "compare" },
    { "name": "offset", "type": "enum", "default": Zero, "values": [Zero, Center, Normalize] },
    { "name": "as", "type": "string", "array": true, "length": 2, "default": DefOutput }
  ]
};

var prototype$12 = inherits(Stack, Transform);

prototype$12.transform = function(_, pulse) {
  var as = _.as || DefOutput,
      y0 = as[0],
      y1 = as[1],
      sort = stableCompare(_.sort),
      field = _.field || one,
      stack = _.offset === Center ? stackCenter
            : _.offset === Normalize ? stackNormalize
            : stackZero,
      groups, i, n, max;

  // partition, sum, and sort the stack groups
  groups = partition$2(pulse.source, _.groupby, sort, field);

  // compute stack layouts per group
  for (i=0, n=groups.length, max=groups.max; i<n; ++i) {
    stack(groups[i], max, field, y0, y1);
  }

  return pulse.reflow(_.modified()).modifies(as);
};

function stackCenter(group, max, field, y0, y1) {
  var last = (max - group.sum) / 2,
      m = group.length,
      j = 0, t;

  for (; j<m; ++j) {
    t = group[j];
    t[y0] = last;
    t[y1] = (last += Math.abs(field(t)));
  }
}

function stackNormalize(group, max, field, y0, y1) {
  var scale = 1 / group.sum,
      last = 0,
      m = group.length,
      j = 0, v = 0, t;

  for (; j<m; ++j) {
    t = group[j];
    t[y0] = last;
    t[y1] = last = scale * (v += Math.abs(field(t)));
  }
}

function stackZero(group, max, field, y0, y1) {
  var lastPos = 0,
      lastNeg = 0,
      m = group.length,
      j = 0, v, t;

  for (; j<m; ++j) {
    t = group[j];
    v = +field(t);
    if (v < 0) {
      t[y0] = lastNeg;
      t[y1] = (lastNeg += v);
    } else {
      t[y0] = lastPos;
      t[y1] = (lastPos += v);
    }
  }
}

function partition$2(data, groupby, sort, field) {
  var groups = [],
      get = function(f) { return f(t); },
      map, i, n, m, t, k, g, s, max;

  // partition data points into stack groups
  if (groupby == null) {
    groups.push(data.slice());
  } else {
    for (map={}, i=0, n=data.length; i<n; ++i) {
      t = data[i];
      k = groupby.map(get);
      g = map[k];
      if (!g) {
        map[k] = (g = []);
        groups.push(g);
      }
      g.push(t);
    }
  }

  // compute sums of groups, sort groups as needed
  for (k=0, max=0, m=groups.length; k<m; ++k) {
    g = groups[k];
    for (i=0, s=0, n=g.length; i<n; ++i) {
      s += Math.abs(field(g[i]));
    }
    g.sum = s;
    if (s > max) max = s;
    if (sort) g.sort(sort);
  }
  groups.max = max;

  return groups;
}



var encode = /*#__PURE__*/Object.freeze({
  __proto__: null,
  axisticks: AxisTicks,
  datajoin: DataJoin,
  encode: Encode,
  legendentries: LegendEntries,
  linkpath: LinkPath,
  pie: Pie,
  scale: Scale,
  sortitems: SortItems,
  stack: Stack,
  validTicks: validTicks
});

function noop$1() {}

const cases = [
  [],
  [[[1.0, 1.5], [0.5, 1.0]]],
  [[[1.5, 1.0], [1.0, 1.5]]],
  [[[1.5, 1.0], [0.5, 1.0]]],
  [[[1.0, 0.5], [1.5, 1.0]]],
  [[[1.0, 1.5], [0.5, 1.0]], [[1.0, 0.5], [1.5, 1.0]]],
  [[[1.0, 0.5], [1.0, 1.5]]],
  [[[1.0, 0.5], [0.5, 1.0]]],
  [[[0.5, 1.0], [1.0, 0.5]]],
  [[[1.0, 1.5], [1.0, 0.5]]],
  [[[0.5, 1.0], [1.0, 0.5]], [[1.5, 1.0], [1.0, 1.5]]],
  [[[1.5, 1.0], [1.0, 0.5]]],
  [[[0.5, 1.0], [1.5, 1.0]]],
  [[[1.0, 1.5], [1.5, 1.0]]],
  [[[0.5, 1.0], [1.0, 1.5]]],
  []
];

// Implementation adapted from d3/d3-contour. Thanks!
function contours() {
  var dx = 1,
      dy = 1,
      smooth = smoothLinear;

  function contours(values, tz) {
    return tz.map(value => contour(values, value));
  }

  // Accumulate, smooth contour rings, assign holes to exterior rings.
  // Based on https://github.com/mbostock/shapefile/blob/v0.6.2/shp/polygon.js
  function contour(values, value) {
    var polygons = [],
        holes = [];

    isorings(values, value, function(ring) {
      smooth(ring, values, value);
      if (area$2(ring) > 0) polygons.push([ring]);
      else holes.push(ring);
    });

    holes.forEach(function(hole) {
      for (var i = 0, n = polygons.length, polygon; i < n; ++i) {
        if (contains((polygon = polygons[i])[0], hole) !== -1) {
          polygon.push(hole);
          return;
        }
      }
    });

    return {
      type: 'MultiPolygon',
      value: value,
      coordinates: polygons
    };
  }

  // Marching squares with isolines stitched into rings.
  // Based on https://github.com/topojson/topojson-client/blob/v3.0.0/src/stitch.js
  function isorings(values, value, callback) {
    var fragmentByStart = new Array,
        fragmentByEnd = new Array,
        x, y, t0, t1, t2, t3;

    // Special case for the first row (y = -1, t2 = t3 = 0).
    x = y = -1;
    t1 = values[0] >= value;
    cases[t1 << 1].forEach(stitch);
    while (++x < dx - 1) {
      t0 = t1, t1 = values[x + 1] >= value;
      cases[t0 | t1 << 1].forEach(stitch);
    }
    cases[t1 << 0].forEach(stitch);

    // General case for the intermediate rows.
    while (++y < dy - 1) {
      x = -1;
      t1 = values[y * dx + dx] >= value;
      t2 = values[y * dx] >= value;
      cases[t1 << 1 | t2 << 2].forEach(stitch);
      while (++x < dx - 1) {
        t0 = t1, t1 = values[y * dx + dx + x + 1] >= value;
        t3 = t2, t2 = values[y * dx + x + 1] >= value;
        cases[t0 | t1 << 1 | t2 << 2 | t3 << 3].forEach(stitch);
      }
      cases[t1 | t2 << 3].forEach(stitch);
    }

    // Special case for the last row (y = dy - 1, t0 = t1 = 0).
    x = -1;
    t2 = values[y * dx] >= value;
    cases[t2 << 2].forEach(stitch);
    while (++x < dx - 1) {
      t3 = t2, t2 = values[y * dx + x + 1] >= value;
      cases[t2 << 2 | t3 << 3].forEach(stitch);
    }
    cases[t2 << 3].forEach(stitch);

    function stitch(line) {
      var start = [line[0][0] + x, line[0][1] + y],
          end = [line[1][0] + x, line[1][1] + y],
          startIndex = index(start),
          endIndex = index(end),
          f, g;
      if (f = fragmentByEnd[startIndex]) {
        if (g = fragmentByStart[endIndex]) {
          delete fragmentByEnd[f.end];
          delete fragmentByStart[g.start];
          if (f === g) {
            f.ring.push(end);
            callback(f.ring);
          } else {
            fragmentByStart[f.start] = fragmentByEnd[g.end] = {start: f.start, end: g.end, ring: f.ring.concat(g.ring)};
          }
        } else {
          delete fragmentByEnd[f.end];
          f.ring.push(end);
          fragmentByEnd[f.end = endIndex] = f;
        }
      } else if (f = fragmentByStart[endIndex]) {
        if (g = fragmentByEnd[startIndex]) {
          delete fragmentByStart[f.start];
          delete fragmentByEnd[g.end];
          if (f === g) {
            f.ring.push(end);
            callback(f.ring);
          } else {
            fragmentByStart[g.start] = fragmentByEnd[f.end] = {start: g.start, end: f.end, ring: g.ring.concat(f.ring)};
          }
        } else {
          delete fragmentByStart[f.start];
          f.ring.unshift(start);
          fragmentByStart[f.start = startIndex] = f;
        }
      } else {
        fragmentByStart[startIndex] = fragmentByEnd[endIndex] = {start: startIndex, end: endIndex, ring: [start, end]};
      }
    }
  }

  function index(point) {
    return point[0] * 2 + point[1] * (dx + 1) * 4;
  }

  function smoothLinear(ring, values, value) {
    ring.forEach(function(point) {
      var x = point[0],
          y = point[1],
          xt = x | 0,
          yt = y | 0,
          v0,
          v1 = values[yt * dx + xt];
      if (x > 0 && x < dx && xt === x) {
        v0 = values[yt * dx + xt - 1];
        point[0] = x + (value - v0) / (v1 - v0) - 0.5;
      }
      if (y > 0 && y < dy && yt === y) {
        v0 = values[(yt - 1) * dx + xt];
        point[1] = y + (value - v0) / (v1 - v0) - 0.5;
      }
    });
  }

  contours.contour = contour;

  contours.size = function(_) {
    if (!arguments.length) return [dx, dy];
    var _0 = Math.ceil(_[0]), _1 = Math.ceil(_[1]);
    if (!(_0 > 0) || !(_1 > 0)) error('invalid size');
    return dx = _0, dy = _1, contours;
  };

  contours.smooth = function(_) {
    return arguments.length ? (smooth = _ ? smoothLinear : noop$1, contours) : smooth === smoothLinear;
  };

  return contours;
}

function area$2(ring) {
  var i = 0,
      n = ring.length,
      area = ring[n - 1][1] * ring[0][0] - ring[n - 1][0] * ring[0][1];
  while (++i < n) area += ring[i - 1][1] * ring[i][0] - ring[i - 1][0] * ring[i][1];
  return area;
}

function contains(ring, hole) {
  var i = -1, n = hole.length, c;
  while (++i < n) if (c = ringContains(ring, hole[i])) return c;
  return 0;
}

function ringContains(ring, point) {
  var x = point[0], y = point[1], contains = -1;
  for (var i = 0, n = ring.length, j = n - 1; i < n; j = i++) {
    var pi = ring[i], xi = pi[0], yi = pi[1], pj = ring[j], xj = pj[0], yj = pj[1];
    if (segmentContains(pi, pj, point)) return 0;
    if (((yi > y) !== (yj > y)) && ((x < (xj - xi) * (y - yi) / (yj - yi) + xi))) contains = -contains;
  }
  return contains;
}

function segmentContains(a, b, c) {
  var i; return collinear(a, b, c) && within(a[i = +(a[0] === b[0])], c[i], b[i]);
}

function collinear(a, b, c) {
  return (b[0] - a[0]) * (c[1] - a[1]) === (c[0] - a[0]) * (b[1] - a[1]);
}

function within(p, q, r) {
  return p <= q && q <= r || r <= q && q <= p;
}

function quantize$1(k, nice, zero) {
  return function(values) {
    var ex = extent(values),
        start = zero ? Math.min(ex[0], 0) : ex[0],
        stop = ex[1],
        span = stop - start,
        step = nice ? tickStep(start, stop, k) : (span / (k + 1));
    return sequence(step, stop, step);
  };
}

/**
 * Generate isocontours (level sets) based on input raster grid data.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} [params.field] - The field with raster grid
 *   data. If unspecified, the tuple itself is interpreted as a raster grid.
 * @param {Array<number>} [params.thresholds] - Contour threshold array. If
 *   specified, the levels, nice, resolve, and zero parameters are ignored.
 * @param {number} [params.levels] - The desired number of contour levels.
 * @param {boolean} [params.nice] - Boolean flag indicating if the contour
 *   threshold values should be automatically aligned to "nice"
 *   human-friendly values. Setting this flag may cause the number of
 *   thresholds to deviate from the specified levels.
 * @param {string} [params.resolve] - The method for resolving thresholds
 *   across multiple input grids. If 'independent' (the default), threshold
 *   calculation will be performed separately for each grid. If 'shared', a
 *   single set of threshold values will be used for all input grids.
 * @param {boolean} [params.zero] - Boolean flag indicating if the contour
 *   threshold values should include zero.
 * @param {boolean} [params.smooth] - Boolean flag indicating if the contour
 *   polygons should be smoothed using linear interpolation. The default is
 *   true. The parameter is ignored when using density estimation.
 * @param {boolean} [params.scale] - Optional numerical value by which to
 *   scale the output isocontour coordinates. This parameter can be useful
 *   to scale the contours to match a desired output resolution.
 * @param {string} [params.as='contour'] - The output field in which to store
 *   the generated isocontour data (default 'contour').
 */
function Isocontour(params) {
  Transform.call(this, null, params);
}

Isocontour.Definition = {
  "type": "Isocontour",
  "metadata": {"generates": true},
  "params": [
    { "name": "field", "type": "field" },
    { "name": "thresholds", "type": "number", "array": true },
    { "name": "levels", "type": "number" },
    { "name": "nice", "type": "boolean", "default": false },
    { "name": "resolve", "type": "enum", "values": ["shared", "independent"], "default": "independent" },
    { "name": "zero", "type": "boolean", "default": true },
    { "name": "smooth", "type": "boolean", "default": true },
    { "name": "scale", "type": "number", "expr": true },
    { "name": "translate", "type": "number", "array": true, "expr": true },
    { "name": "as", "type": "string", "null": true, "default": "contour" }
  ]
};

var prototype$13 = inherits(Isocontour, Transform);

prototype$13.transform = function(_, pulse) {
  if (this.value && !pulse.changed() && !_.modified()) {
    return pulse.StopPropagation;
  }

  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS),
      source = pulse.materialize(pulse.SOURCE).source,
      field = _.field || identity,
      contour = contours().smooth(_.smooth !== false),
      tz = _.thresholds || levels(source, field, _),
      as = _.as === null ? null : _.as || 'contour',
      values = [];

  source.forEach(t => {
    const grid = field(t);

    // generate contour paths in GeoJSON format
    const paths = contour.size([grid.width, grid.height])(
      grid.values, isArray(tz) ? tz : tz(grid.values)
    );

    // adjust contour path coordinates as needed
    transformPaths(paths, grid, t, _);

    // ingest; copy source data properties to output
    paths.forEach(p => {
      values.push(rederive(t, ingest(as != null ? {[as]: p} : p)));
    });
  });

  if (this.value) out.rem = this.value;
  this.value = out.source = out.add = values;

  return out;
};

function levels(values, f, _) {
  const q = quantize$1(_.levels || 10, _.nice, _.zero !== false);
  return _.resolve !== 'shared'
    ? q
    : q(values.map(t => max(f(t).values)));
}

function transformPaths(paths, grid, datum, _) {
  let s = _.scale || grid.scale,
      t = _.translate || grid.translate;
  if (isFunction(s)) s = s(datum, _);
  if (isFunction(t)) t = t(datum, _);
  if ((s === 1 || s == null) && !t) return;

  const sx = (isNumber(s) ? s : s[0]) || 1,
        sy = (isNumber(s) ? s : s[1]) || 1,
        tx = t && t[0] || 0,
        ty = t && t[1] || 0;

  paths.forEach(transform$1(grid, sx, sy, tx, ty));
}

function transform$1(grid, sx, sy, tx, ty) {
  const x1 = grid.x1 || 0,
        y1 = grid.y1 || 0,
        flip = sx * sy < 0;

  function transformPolygon(coordinates) {
    coordinates.forEach(transformRing);
  }

  function transformRing(coordinates) {
    if (flip) coordinates.reverse(); // maintain winding order
    coordinates.forEach(transformPoint);
  }

  function transformPoint(coordinates) {
    coordinates[0] = (coordinates[0] - x1) * sx + tx;
    coordinates[1] = (coordinates[1] - y1) * sy + ty;
  }

  return function(geometry) {
    geometry.coordinates.forEach(transformPolygon);
    return geometry;
  };
}

function radius(bw, data, f) {
  const v = bw >= 0 ? bw : bandwidthNRD(data, f);
  return Math.round((Math.sqrt(4 * v * v + 1) - 1) / 2);
}

function number$4(_) {
  return isFunction(_) ? _ : constant(+_);
}

// Implementation adapted from d3/d3-contour. Thanks!
function density2D() {
  var x = d => d[0],
      y = d => d[1],
      weight = one,
      bandwidth = [-1, -1],
      dx = 960,
      dy = 500,
      k = 2; // log2(cellSize)

  function density(data, counts) {
    const rx = radius(bandwidth[0], data, x) >> k, // blur x-radius
          ry = radius(bandwidth[1], data, y) >> k, // blur y-radius
          ox = rx ? rx + 2 : 0, // x-offset padding for blur
          oy = ry ? ry + 2 : 0, // y-offset padding for blur
          n = 2 * ox + (dx >> k), // grid width
          m = 2 * oy + (dy >> k), // grid height
          values0 = new Float32Array(n * m),
          values1 = new Float32Array(n * m);

    let values = values0;

    data.forEach(d => {
      const xi = ox + (+x(d) >> k),
            yi = oy + (+y(d) >> k);

      if (xi >= 0 && xi < n && yi >= 0 && yi < m) {
        values0[xi + yi * n] += +weight(d);
      }
    });

    if (rx > 0 && ry > 0) {
      blurX(n, m, values0, values1, rx);
      blurY(n, m, values1, values0, ry);
      blurX(n, m, values0, values1, rx);
      blurY(n, m, values1, values0, ry);
      blurX(n, m, values0, values1, rx);
      blurY(n, m, values1, values0, ry);
    } else if (rx > 0) {
      blurX(n, m, values0, values1, rx);
      blurX(n, m, values1, values0, rx);
      blurX(n, m, values0, values1, rx);
      values = values1;
    } else if (ry > 0) {
      blurY(n, m, values0, values1, ry);
      blurY(n, m, values1, values0, ry);
      blurY(n, m, values0, values1, ry);
      values = values1;
    }

    // scale density estimates
    // density in points per square pixel or probability density
    let s = counts ? Math.pow(2, -2 * k) : 1 / sum(values);
    for (let i=0, sz=n*m; i<sz; ++i) values[i] *= s;

    return {
      values: values,
      scale: 1 << k,
      width: n,
      height: m,
      x1: ox,
      y1: oy,
      x2: ox + (dx >> k),
      y2: oy + (dy >> k)
    };
  }

  density.x = function(_) {
    return arguments.length ? (x = number$4(_), density) : x;
  };

  density.y = function(_) {
    return arguments.length ? (y = number$4(_), density) : y;
  };

  density.weight = function(_) {
    return arguments.length ? (weight = number$4(_), density) : weight;
  };

  density.size = function(_) {
    if (!arguments.length) return [dx, dy];
    var _0 = Math.ceil(_[0]), _1 = Math.ceil(_[1]);
    if (!(_0 >= 0) && !(_0 >= 0)) error('invalid size');
    return dx = _0, dy = _1, density;
  };

  density.cellSize = function(_) {
    if (!arguments.length) return 1 << k;
    if (!((_ = +_) >= 1)) error('invalid cell size');
    k = Math.floor(Math.log(_) / Math.LN2);
    return density;
  };

  density.bandwidth = function(_) {
    if (!arguments.length) return bandwidth;
    _ = array(_);
    if (_.length === 1) _ = [+_[0], +_[0]];
    if (_.length !== 2) error('invalid bandwidth');
    return bandwidth = _, density;
  };

  return density;
}

function blurX(n, m, source, target, r) {
  const w = (r << 1) + 1;
  for (let j = 0; j < m; ++j) {
    for (let i = 0, sr = 0; i < n + r; ++i) {
      if (i < n) {
        sr += source[i + j * n];
      }
      if (i >= r) {
        if (i >= w) {
          sr -= source[i - w + j * n];
        }
        target[i - r + j * n] = sr / Math.min(i + 1, n - 1 + w - i, w);
      }
    }
  }
}

function blurY(n, m, source, target, r) {
  const w = (r << 1) + 1;
  for (let i = 0; i < n; ++i) {
    for (let j = 0, sr = 0; j < m + r; ++j) {
      if (j < m) {
        sr += source[i + j * n];
      }
      if (j >= r) {
        if (j >= w) {
          sr -= source[i + (j - w) * n];
        }
        target[i + (j - r) * n] = sr / Math.min(j + 1, m - 1 + w - j, w);
      }
    }
  }
}

/**
 * Perform 2D kernel-density estimation of point data.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<number>} params.size - The [width, height] extent (in
 *   units of input pixels) over which to perform density estimation.
 * @param {function(object): number} params.x - The x-coordinate accessor.
 * @param {function(object): number} params.y - The y-coordinate accessor.
 * @param {function(object): number} [params.weight] - The weight accessor.
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors
 *   to groupby.
 * @param {number} [params.cellSize] - Contour density calculation cell size.
 *   This parameter determines the level of spatial approximation. For example,
 *   the default value of 4 maps to 2x reductions in both x- and y- dimensions.
 *   A value of 1 will result in an output raster grid whose dimensions exactly
 *   matches the size parameter.
 * @param {Array<number>} [params.bandwidth] - The KDE kernel bandwidths,
 *   in pixels. The input can be a two-element array specifying separate
 *   x and y bandwidths, or a single-element array specifying both. If the
 *   bandwidth is unspecified or less than zero, the bandwidth will be
 *   automatically determined.
 * @param {boolean} [params.counts=false] - A boolean flag indicating if the
 *   output values should be probability estimates (false, default) or
 *   smoothed counts (true).
 * @param {string} [params.as='grid'] - The output field in which to store
 *   the generated raster grid (default 'grid').
 */
function KDE2D(params) {
  Transform.call(this, null, params);
}

KDE2D.Definition = {
  "type": "KDE2D",
  "metadata": {"generates": true},
  "params": [
    { "name": "size", "type": "number", "array": true, "length": 2, "required": true },
    { "name": "x", "type": "field", "required": true },
    { "name": "y", "type": "field", "required": true },
    { "name": "weight", "type": "field" },
    { "name": "groupby", "type": "field", "array": true },
    { "name": "cellSize", "type": "number" },
    { "name": "bandwidth", "type": "number", "array": true, "length": 2 },
    { "name": "counts", "type": "boolean", "default": false },
    { "name": "as", "type": "string", "default": "grid"}
  ]
};

var prototype$14 = inherits(KDE2D, Transform);

const PARAMS = ['x', 'y', 'weight', 'size', 'cellSize', 'bandwidth'];

function params(obj, _) {
  PARAMS.forEach(param => _[param] != null ? obj[param](_[param]) : 0);
  return obj;
}

prototype$14.transform = function(_, pulse) {
  if (this.value && !pulse.changed() && !_.modified())
    return pulse.StopPropagation;

  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS),
      source = pulse.materialize(pulse.SOURCE).source,
      groups = partition$3(source, _.groupby),
      names = (_.groupby || []).map(accessorName),
      kde = params(density2D(), _),
      as = _.as || 'grid',
      values = [];

  function set(t, vals) {
    for (let i=0; i<names.length; ++i) t[names[i]] = vals[i];
    return t;
  }

  // generate density raster grids
  values = groups.map(g => ingest(
    set({[as]: kde(g, _.counts)}, g.dims)
  ));

  if (this.value) out.rem = this.value;
  this.value = out.source = out.add = values;

  return out;
};

function partition$3(data, groupby) {
  var groups = [],
      get = f => f(t),
      map, i, n, t, k, g;

  // partition data points into groups
  if (groupby == null) {
    groups.push(data);
  } else {
    for (map={}, i=0, n=data.length; i<n; ++i) {
      t = data[i];
      k = groupby.map(get);
      g = map[k];
      if (!g) {
        map[k] = (g = []);
        g.dims = k;
        groups.push(g);
      }
      g.push(t);
    }
  }

  return groups;
}

/**
 * Generate contours based on kernel-density estimation of point data.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<number>} params.size - The dimensions [width, height] over which to compute contours.
 *  If the values parameter is provided, this must be the dimensions of the input data.
 *  If density estimation is performed, this is the output view dimensions in pixels.
 * @param {Array<number>} [params.values] - An array of numeric values representing an
 *  width x height grid of values over which to compute contours. If unspecified, this
 *  transform will instead attempt to compute contours for the kernel density estimate
 *  using values drawn from data tuples in the input pulse.
 * @param {function(object): number} [params.x] - The pixel x-coordinate accessor for density estimation.
 * @param {function(object): number} [params.y] - The pixel y-coordinate accessor for density estimation.
 * @param {function(object): number} [params.weight] - The data point weight accessor for density estimation.
 * @param {number} [params.cellSize] - Contour density calculation cell size.
 * @param {number} [params.bandwidth] - Kernel density estimation bandwidth.
 * @param {Array<number>} [params.thresholds] - Contour threshold array. If
 *   this parameter is set, the count and nice parameters will be ignored.
 * @param {number} [params.count] - The desired number of contours.
 * @param {boolean} [params.nice] - Boolean flag indicating if the contour
 *   threshold values should be automatically aligned to "nice"
 *   human-friendly values. Setting this flag may cause the number of
 *   thresholds to deviate from the specified count.
 * @param {boolean} [params.smooth] - Boolean flag indicating if the contour
 *   polygons should be smoothed using linear interpolation. The default is
 *   true. The parameter is ignored when using density estimation.
 */
function Contour(params) {
  Transform.call(this, null, params);
}

Contour.Definition = {
  "type": "Contour",
  "metadata": {"generates": true},
  "params": [
    { "name": "size", "type": "number", "array": true, "length": 2, "required": true },
    { "name": "values", "type": "number", "array": true },
    { "name": "x", "type": "field" },
    { "name": "y", "type": "field" },
    { "name": "weight", "type": "field" },
    { "name": "cellSize", "type": "number" },
    { "name": "bandwidth", "type": "number" },
    { "name": "count", "type": "number" },
    { "name": "nice", "type": "boolean", "default": false },
    { "name": "thresholds", "type": "number", "array": true },
    { "name": "smooth", "type": "boolean", "default": true }
  ]
};

var prototype$15 = inherits(Contour, Transform);

prototype$15.transform = function(_, pulse) {
  if (this.value && !pulse.changed() && !_.modified()) {
    return pulse.StopPropagation;
  }

  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS),
      contour = contours().smooth(_.smooth !== false),
      values = _.values,
      thresh = _.thresholds || quantize$1(_.count || 10, _.nice, !!values),
      size = _.size, grid, post;

  if (!values) {
    values = pulse.materialize(pulse.SOURCE).source;
    grid = params(density2D(), _)(values, true);
    post = transform$1(grid, grid.scale || 1, grid.scale || 1, 0, 0);
    size = [grid.width, grid.height];
    values = grid.values;
  }

  thresh = isArray(thresh) ? thresh : thresh(values);
  values = contour.size(size)(values, thresh);
  if (post) values.forEach(post);

  if (this.value) out.rem = this.value;
  this.value = out.source = out.add = (values || []).map(ingest);

  return out;
};

var Feature = 'Feature';
var FeatureCollection = 'FeatureCollection';
var MultiPoint = 'MultiPoint';

/**
 * Consolidate an array of [longitude, latitude] points or GeoJSON features
 * into a combined GeoJSON object. This transform is particularly useful for
 * combining geo data for a Projection's fit argument. The resulting GeoJSON
 * data is available as this transform's value. Input pulses are unchanged.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<function(object): *>} [params.fields] - A two-element array
 *   of field accessors for the longitude and latitude values.
 * @param {function(object): *} params.geojson - A field accessor for
 *   retrieving GeoJSON feature data.
 */
function GeoJSON(params) {
  Transform.call(this, null, params);
}

GeoJSON.Definition = {
  "type": "GeoJSON",
  "metadata": {},
  "params": [
    { "name": "fields", "type": "field", "array": true, "length": 2 },
    { "name": "geojson", "type": "field" },
  ]
};

var prototype$16 = inherits(GeoJSON, Transform);

prototype$16.transform = function(_, pulse) {
  var features = this._features,
      points = this._points,
      fields = _.fields,
      lon = fields && fields[0],
      lat = fields && fields[1],
      geojson = _.geojson || (!fields && identity),
      flag = pulse.ADD,
      mod;

  mod = _.modified()
    || pulse.changed(pulse.REM)
    || pulse.modified(accessorFields(geojson))
    || (lon && (pulse.modified(accessorFields(lon))))
    || (lat && (pulse.modified(accessorFields(lat))));

  if (!this.value || mod) {
    flag = pulse.SOURCE;
    this._features = (features = []);
    this._points = (points = []);
  }

  if (geojson) {
    pulse.visit(flag, function(t) {
      features.push(geojson(t));
    });
  }

  if (lon && lat) {
    pulse.visit(flag, function(t) {
      var x = lon(t),
          y = lat(t);
      if (x != null && y != null && (x = +x) === x && (y = +y) === y) {
        points.push([x, y]);
      }
    });
    features = features.concat({
      type: Feature,
      geometry: {
        type: MultiPoint,
        coordinates: points
      }
    });
  }

  this.value = {
    type: FeatureCollection,
    features: features
  };
};

var abs = Math.abs;
var cos = Math.cos;
var sin = Math.sin;

var epsilon$1 = 1e-6;
var pi = Math.PI;
var halfPi = pi / 2;
var sqrt2 = sqrt$1(2);

function asin(x) {
  return x > 1 ? halfPi : x < -1 ? -halfPi : Math.asin(x);
}

function sqrt$1(x) {
  return x > 0 ? Math.sqrt(x) : 0;
}

function mollweideBromleyTheta(cp, phi) {
  var cpsinPhi = cp * sin(phi), i = 30, delta;
  do phi -= delta = (phi + sin(phi) - cpsinPhi) / (1 + cos(phi));
  while (abs(delta) > epsilon$1 && --i > 0);
  return phi / 2;
}

function mollweideBromleyRaw(cx, cy, cp) {

  function forward(lambda, phi) {
    return [cx * lambda * cos(phi = mollweideBromleyTheta(cp, phi)), cy * sin(phi)];
  }

  forward.invert = function(x, y) {
    return y = asin(y / cy), [x / (cx * cos(y)), asin((2 * y + sin(2 * y)) / cp)];
  };

  return forward;
}

var mollweideRaw = mollweideBromleyRaw(sqrt2 / halfPi, sqrt2, pi);

function geoMollweide() {
  return geoProjection(mollweideRaw)
      .scale(169.529);
}

var defaultPath = geoPath();

var projectionProperties = [
  // standard properties in d3-geo
  'clipAngle',
  'clipExtent',
  'scale',
  'translate',
  'center',
  'rotate',
  'parallels',
  'precision',
  'reflectX',
  'reflectY',

  // extended properties in d3-geo-projections
  'coefficient',
  'distance',
  'fraction',
  'lobes',
  'parallel',
  'radius',
  'ratio',
  'spacing',
  'tilt'
];

/**
 * Augment projections with their type and a copy method.
 */
function create$1(type, constructor) {
  return function projection() {
    var p = constructor();

    p.type = type;

    p.path = geoPath().projection(p);

    p.copy = p.copy || function() {
      var c = projection();
      projectionProperties.forEach(function(prop) {
        if (p[prop]) c[prop](p[prop]());
      });
      c.path.pointRadius(p.path.pointRadius());
      return c;
    };

    return p;
  };
}

function projection(type, proj) {
  if (!type || typeof type !== 'string') {
    throw new Error('Projection type must be a name string.');
  }
  type = type.toLowerCase();
  if (arguments.length > 1) {
    projections[type] = create$1(type, proj);
    return this;
  } else {
    return projections[type] || null;
  }
}

function getProjectionPath(proj) {
  return (proj && proj.path) || defaultPath;
}

var projections = {
  // base d3-geo projection types
  albers:               geoAlbers,
  albersusa:            geoAlbersUsa,
  azimuthalequalarea:   geoAzimuthalEqualArea,
  azimuthalequidistant: geoAzimuthalEquidistant,
  conicconformal:       geoConicConformal,
  conicequalarea:       geoConicEqualArea,
  conicequidistant:     geoConicEquidistant,
  equalEarth:           geoEqualEarth,
  equirectangular:      geoEquirectangular,
  gnomonic:             geoGnomonic,
  identity:             geoIdentity,
  mercator:             geoMercator,
  mollweide:            geoMollweide,
  naturalEarth1:        geoNaturalEarth1,
  orthographic:         geoOrthographic,
  stereographic:        geoStereographic,
  transversemercator:   geoTransverseMercator
};

for (var key$1 in projections) {
  projection(key$1, projections[key$1]);
}

/**
 * Map GeoJSON data to an SVG path string.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(number, number): *} params.projection - The cartographic
 *   projection to apply.
 * @param {function(object): *} [params.field] - The field with GeoJSON data,
 *   or null if the tuple itself is a GeoJSON feature.
 * @param {string} [params.as='path'] - The output field in which to store
 *   the generated path data (default 'path').
 */
function GeoPath(params) {
  Transform.call(this, null, params);
}

GeoPath.Definition = {
  "type": "GeoPath",
  "metadata": {"modifies": true},
  "params": [
    { "name": "projection", "type": "projection" },
    { "name": "field", "type": "field" },
    { "name": "pointRadius", "type": "number", "expr": true },
    { "name": "as", "type": "string", "default": "path" }
  ]
};

var prototype$17 = inherits(GeoPath, Transform);

prototype$17.transform = function(_, pulse) {
  var out = pulse.fork(pulse.ALL),
      path = this.value,
      field = _.field || identity,
      as = _.as || 'path',
      flag = out.SOURCE;

  function set(t) { t[as] = path(field(t)); }

  if (!path || _.modified()) {
    // parameters updated, reset and reflow
    this.value = path = getProjectionPath(_.projection);
    out.materialize().reflow();
  } else {
    flag = field === identity || pulse.modified(field.fields)
      ? out.ADD_MOD
      : out.ADD;
  }

  var prev = initPath(path, _.pointRadius);
  out.visit(flag, set);
  path.pointRadius(prev);

  return out.modifies(as);
};

function initPath(path, pointRadius) {
  var prev = path.pointRadius();
  path.context(null);
  if (pointRadius != null) {
    path.pointRadius(pointRadius);
  }
  return prev;
}

/**
 * Geo-code a longitude/latitude point to an x/y coordinate.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(number, number): *} params.projection - The cartographic
 *   projection to apply.
 * @param {Array<function(object): *>} params.fields - A two-element array of
 *   field accessors for the longitude and latitude values.
 * @param {Array<string>} [params.as] - A two-element array of field names
 *   under which to store the result. Defaults to ['x','y'].
 */
function GeoPoint(params) {
  Transform.call(this, null, params);
}

GeoPoint.Definition = {
  "type": "GeoPoint",
  "metadata": {"modifies": true},
  "params": [
    { "name": "projection", "type": "projection", "required": true },
    { "name": "fields", "type": "field", "array": true, "required": true, "length": 2 },
    { "name": "as", "type": "string", "array": true, "length": 2, "default": ["x", "y"] }
  ]
};

var prototype$18 = inherits(GeoPoint, Transform);

prototype$18.transform = function(_, pulse) {
  var proj = _.projection,
      lon = _.fields[0],
      lat = _.fields[1],
      as = _.as || ['x', 'y'],
      x = as[0],
      y = as[1],
      mod;

  function set(t) {
    var xy = proj([lon(t), lat(t)]);
    if (xy) {
      t[x] = xy[0];
      t[y] = xy[1];
    } else {
      t[x] = undefined;
      t[y] = undefined;
    }
  }

  if (_.modified()) {
    // parameters updated, reflow
    pulse = pulse.materialize().reflow(true).visit(pulse.SOURCE, set);
  } else {
    mod = pulse.modified(lon.fields) || pulse.modified(lat.fields);
    pulse.visit(mod ? pulse.ADD_MOD : pulse.ADD, set);
  }

  return pulse.modifies(as);
};

/**
 * Annotate items with a geopath shape generator.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(number, number): *} params.projection - The cartographic
 *   projection to apply.
 * @param {function(object): *} [params.field] - The field with GeoJSON data,
 *   or null if the tuple itself is a GeoJSON feature.
 * @param {string} [params.as='shape'] - The output field in which to store
 *   the generated path data (default 'shape').
 */
function GeoShape(params) {
  Transform.call(this, null, params);
}

GeoShape.Definition = {
  "type": "GeoShape",
  "metadata": {"modifies": true, "nomod": true},
  "params": [
    { "name": "projection", "type": "projection" },
    { "name": "field", "type": "field", "default": "datum" },
    { "name": "pointRadius", "type": "number", "expr": true },
    { "name": "as", "type": "string", "default": "shape" }
  ]
};

var prototype$19 = inherits(GeoShape, Transform);

prototype$19.transform = function(_, pulse) {
  var out = pulse.fork(pulse.ALL),
      shape = this.value,
      as = _.as || 'shape',
      flag = out.ADD;

  if (!shape || _.modified()) {
    // parameters updated, reset and reflow
    this.value = shape = shapeGenerator(
      getProjectionPath(_.projection),
      _.field || field('datum'),
      _.pointRadius
    );
    out.materialize().reflow();
    flag = out.SOURCE;
  }

  out.visit(flag, function(t) { t[as] = shape; });

  return out.modifies(as);
};

function shapeGenerator(path, field, pointRadius) {
  var shape = pointRadius == null
    ? function(_) { return path(field(_)); }
    : function(_) {
      var prev = path.pointRadius(),
          value = path.pointRadius(pointRadius)(field(_));
      path.pointRadius(prev);
      return value;
    };
  shape.context = function(_) {
    path.context(_);
    return shape;
  };

  return shape;
}

/**
 * GeoJSON feature generator for creating graticules.
 * @constructor
 */
function Graticule(params) {
  Transform.call(this, [], params);
  this.generator = geoGraticule();
}

Graticule.Definition = {
  "type": "Graticule",
  "metadata": {"changes": true, "generates": true},
  "params": [
    { "name": "extent", "type": "array", "array": true, "length": 2,
      "content": {"type": "number", "array": true, "length": 2} },
    { "name": "extentMajor", "type": "array", "array": true, "length": 2,
      "content": {"type": "number", "array": true, "length": 2} },
    { "name": "extentMinor", "type": "array", "array": true, "length": 2,
      "content": {"type": "number", "array": true, "length": 2} },
    { "name": "step", "type": "number", "array": true, "length": 2 },
    { "name": "stepMajor", "type": "number", "array": true, "length": 2, "default": [90, 360] },
    { "name": "stepMinor", "type": "number", "array": true, "length": 2, "default": [10, 10] },
    { "name": "precision", "type": "number", "default": 2.5 }
  ]
};

var prototype$1a = inherits(Graticule, Transform);

prototype$1a.transform = function(_, pulse) {
  var src = this.value,
      gen = this.generator, t;

  if (!src.length || _.modified()) {
    for (var prop in _) {
      if (isFunction(gen[prop])) {
        gen[prop](_[prop]);
      }
    }
  }

  t = gen();
  if (src.length) {
    pulse.mod.push(replace(src[0], t));
  } else {
    pulse.add.push(ingest(t));
  }
  src[0] = t;

  return pulse;
};

/**
 * Render a heatmap image for input raster grid data.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} [params.field] - The field with raster grid
 *   data. If unspecified, the tuple itself is interpreted as a raster grid.
 * @param {string} [params.color] - A constant color value or function for
 *   individual pixel color. If a function, it will be invoked with an input
 *   object that includes $x, $y, $value, and $max fields for the grid.
 * @param {number} [params.opacity] - A constant opacity value or function for
 *   individual pixel opacity. If a function, it will be invoked with an input
 *   object that includes $x, $y, $value, and $max fields for the grid.
 * @param {string} [params.resolve] - The method for resolving maximum values
 *   across multiple input grids. If 'independent' (the default), maximum
 *   calculation will be performed separately for each grid. If 'shared',
 *   a single global maximum will be used for all input grids.
 * @param {string} [params.as='image'] - The output field in which to store
 *   the generated bitmap canvas images (default 'image').
 */
function Heatmap(params) {
  Transform.call(this, null, params);
}

Heatmap.Definition = {
  "type": "heatmap",
  "metadata": {"modifies": true},
  "params": [
    { "name": "field", "type": "field" },
    { "name": "color", "type": "string", "expr": true},
    { "name": "opacity", "type": "number", "expr": true},
    { "name": "resolve", "type": "enum", "values": ["shared", "independent"], "default": "independent" },
    { "name": "as", "type": "string", "default": "image" }
  ]
};

var prototype$1b = inherits(Heatmap, Transform);

prototype$1b.transform = function(_, pulse) {
  if (!pulse.changed() && !_.modified()) {
    return pulse.StopPropagation;
  }

  var source = pulse.materialize(pulse.SOURCE).source,
      shared = _.resolve === 'shared',
      field = _.field || identity,
      opacity = opacity_(_.opacity, _),
      color = color_(_.color, _),
      as = _.as || 'image',
      obj = {
        $x: 0, $y: 0, $value: 0,
        $max: shared ? max(source.map(t => max(field(t).values))) : 0
      };

  source.forEach(t => {
    const v = field(t);

    // build proxy data object
    const o = extend({}, t, obj);
    // set maximum value if not globally shared
    if (!shared) o.$max = max(v.values || []);

    // generate canvas image
    // optimize color/opacity if not pixel-dependent
    t[as] = toCanvas(v, o,
      color.dep ? color : constant(color(o)),
      opacity.dep ? opacity : constant(opacity(o))
    );
  });

  return pulse.reflow(true).modifies(as);
};

// get image color function
function color_(color, _) {
  let f;
  if (isFunction(color)) {
    f = obj => rgb(color(obj, _));
    f.dep = dependency(color);
  } else {
    // default to mid-grey
    f = constant(rgb(color || '#888'));
  }
  return f;
}

// get image opacity function
function opacity_(opacity, _) {
  let f;
  if (isFunction(opacity)) {
    f = obj => opacity(obj, _);
    f.dep = dependency(opacity);
  } else if (opacity) {
    f = constant(opacity);
  } else {
    // default to [0, max] opacity gradient
    f = obj => (obj.$value / obj.$max) || 0;
    f.dep = true;
  }
  return f;
}

// check if function depends on individual pixel data
function dependency(f) {
  if (!isFunction(f)) return false;
  const set = toSet(accessorFields(f));
  return set.$x || set.$y || set.$value || set.$max;
}

// render raster grid to canvas
function toCanvas(grid, obj, color, opacity) {
  const n = grid.width,
        m = grid.height,
        x1 = grid.x1 || 0,
        y1 = grid.y1 || 0,
        x2 = grid.x2 || n,
        y2 = grid.y2 || m,
        val = grid.values,
        value = val ? i => val[i] : zero,
        can = domCanvas(x2 - x1, y2 - y1),
        ctx = can.getContext('2d'),
        img = ctx.getImageData(0, 0, x2 - x1, y2 - y1),
        pix = img.data;

  for (let j=y1, k=0; j<y2; ++j) {
    obj.$y = j - y1;
    for (let i=x1, r=j*n; i<x2; ++i, k+=4) {
      obj.$x = i - x1;
      obj.$value = value(i + r);

      const v = color(obj);
      pix[k+0] = v.r;
      pix[k+1] = v.g;
      pix[k+2] = v.b;
      pix[k+3] = ~~(255 * opacity(obj));
    }
  }

  ctx.putImageData(img, 0, 0);
  return can;
}

/**
 * Maintains a cartographic projection.
 * @constructor
 * @param {object} params - The parameters for this operator.
 */
function Projection(params) {
  Transform.call(this, null, params);
  this.modified(true); // always treat as modified
}

var prototype$1c = inherits(Projection, Transform);

prototype$1c.transform = function(_, pulse) {
  var proj = this.value;

  if (!proj || _.modified('type')) {
    this.value = (proj = create$2(_.type));
    projectionProperties.forEach(function(prop) {
      if (_[prop] != null) set$1(proj, prop, _[prop]);
    });
  } else {
    projectionProperties.forEach(function(prop) {
      if (_.modified(prop)) set$1(proj, prop, _[prop]);
    });
  }

  if (_.pointRadius != null) proj.path.pointRadius(_.pointRadius);
  if (_.fit) fit(proj, _);

  return pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS);
};

function fit(proj, _) {
  var data = collectGeoJSON(_.fit);
  _.extent ? proj.fitExtent(_.extent, data)
    : _.size ? proj.fitSize(_.size, data) : 0;
}

function create$2(type) {
  var constructor = projection((type || 'mercator').toLowerCase());
  if (!constructor) error('Unrecognized projection type: ' + type);
  return constructor();
}

function set$1(proj, key, value) {
   if (isFunction(proj[key])) proj[key](value);
}

function collectGeoJSON(data) {
  data = array(data);
  return data.length === 1 ? data[0]
    : {
        type: FeatureCollection,
        features: data.reduce((a, f) => a.concat(featurize(f)), [])
      };
}

function featurize(f) {
  return f.type === FeatureCollection
    ? f.features
    : array(f).filter(d => d != null).map(
        d => d.type === Feature ? d : {type: Feature, geometry: d}
      );
}



var geo = /*#__PURE__*/Object.freeze({
  __proto__: null,
  contour: Contour,
  geojson: GeoJSON,
  geopath: GeoPath,
  geopoint: GeoPoint,
  geoshape: GeoShape,
  graticule: Graticule,
  heatmap: Heatmap,
  isocontour: Isocontour,
  kde2d: KDE2D,
  projection: Projection
});

var ForceMap = {
  center: forceCenter,
  collide: forceCollide,
  nbody: forceManyBody,
  link: forceLink,
  x: forceX,
  y: forceY
};

var Forces = 'forces',
    ForceParams = [
      'alpha', 'alphaMin', 'alphaTarget',
      'velocityDecay', 'forces'
    ],
    ForceConfig = ['static', 'iterations'],
    ForceOutput = ['x', 'y', 'vx', 'vy'];

/**
 * Force simulation layout.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<object>} params.forces - The forces to apply.
 */
function Force(params) {
  Transform.call(this, null, params);
}

Force.Definition = {
  "type": "Force",
  "metadata": {"modifies": true},
  "params": [
    { "name": "static", "type": "boolean", "default": false },
    { "name": "restart", "type": "boolean", "default": false },
    { "name": "iterations", "type": "number", "default": 300 },
    { "name": "alpha", "type": "number", "default": 1 },
    { "name": "alphaMin", "type": "number", "default": 0.001 },
    { "name": "alphaTarget", "type": "number", "default": 0 },
    { "name": "velocityDecay", "type": "number", "default": 0.4 },
    { "name": "forces", "type": "param", "array": true,
      "params": [
        {
          "key": {"force": "center"},
          "params": [
            { "name": "x", "type": "number", "default": 0 },
            { "name": "y", "type": "number", "default": 0 }
          ]
        },
        {
          "key": {"force": "collide"},
          "params": [
            { "name": "radius", "type": "number", "expr": true },
            { "name": "strength", "type": "number", "default": 0.7 },
            { "name": "iterations", "type": "number", "default": 1 }
          ]
        },
        {
          "key": {"force": "nbody"},
          "params": [
            { "name": "strength", "type": "number", "default": -30 },
            { "name": "theta", "type": "number", "default": 0.9 },
            { "name": "distanceMin", "type": "number", "default": 1 },
            { "name": "distanceMax", "type": "number" }
          ]
        },
        {
          "key": {"force": "link"},
          "params": [
            { "name": "links", "type": "data" },
            { "name": "id", "type": "field" },
            { "name": "distance", "type": "number", "default": 30, "expr": true },
            { "name": "strength", "type": "number", "expr": true },
            { "name": "iterations", "type": "number", "default": 1 }
          ]
        },
        {
          "key": {"force": "x"},
          "params": [
            { "name": "strength", "type": "number", "default": 0.1 },
            { "name": "x", "type": "field" }
          ]
        },
        {
          "key": {"force": "y"},
          "params": [
            { "name": "strength", "type": "number", "default": 0.1 },
            { "name": "y", "type": "field" }
          ]
        }
      ] },
    {
      "name": "as", "type": "string", "array": true, "modify": false,
      "default": ForceOutput
    }
  ]
};

var prototype$1d = inherits(Force, Transform);

prototype$1d.transform = function(_, pulse) {
  var sim = this.value,
      change = pulse.changed(pulse.ADD_REM),
      params = _.modified(ForceParams),
      iters = _.iterations || 300;

  // configure simulation
  if (!sim) {
    this.value = sim = simulation(pulse.source, _);
    sim.on('tick', rerun(pulse.dataflow, this));
    if (!_.static) {
      change = true;
      sim.tick(); // ensure we run on init
    }
    pulse.modifies('index');
  } else {
    if (change) {
      pulse.modifies('index');
      sim.nodes(pulse.source);
    }
    if (params || pulse.changed(pulse.MOD)) {
      setup(sim, _, 0, pulse);
    }
  }

  // run simulation
  if (params || change || _.modified(ForceConfig)
      || (pulse.changed() && _.restart))
  {
    sim.alpha(Math.max(sim.alpha(), _.alpha || 1))
       .alphaDecay(1 - Math.pow(sim.alphaMin(), 1 / iters));

    if (_.static) {
      for (sim.stop(); --iters >= 0;) sim.tick();
    } else {
      if (sim.stopped()) sim.restart();
      if (!change) return pulse.StopPropagation; // defer to sim ticks
    }
  }

  return this.finish(_, pulse);
};

prototype$1d.finish = function(_, pulse) {
  var dataflow = pulse.dataflow;

  // inspect dependencies, touch link source data
  for (var args=this._argops, j=0, m=args.length, arg; j<m; ++j) {
    arg = args[j];
    if (arg.name !== Forces || arg.op._argval.force !== 'link') {
      continue;
    }
    for (var ops=arg.op._argops, i=0, n=ops.length, op; i<n; ++i) {
      if (ops[i].name === 'links' && (op = ops[i].op.source)) {
        dataflow.pulse(op, dataflow.changeset().reflow());
        break;
      }
    }
  }

  // reflow all nodes
  return pulse.reflow(_.modified()).modifies(ForceOutput);
};

function rerun(df, op) {
  return function() { df.touch(op).run(); }
}

function simulation(nodes, _) {
  var sim = forceSimulation(nodes),
      stopped = false,
      stop = sim.stop,
      restart = sim.restart;

  sim.stopped = function() {
    return stopped;
  };
  sim.restart = function() {
    stopped = false;
    return restart();
  };
  sim.stop = function() {
    stopped = true;
    return stop();
  };

  return setup(sim, _, true).on('end', function() { stopped = true; });
}

function setup(sim, _, init, pulse) {
  var f = array(_.forces), i, n, p, name;

  for (i=0, n=ForceParams.length; i<n; ++i) {
    p = ForceParams[i];
    if (p !== Forces && _.modified(p)) sim[p](_[p]);
  }

  for (i=0, n=f.length; i<n; ++i) {
    name = Forces + i;
    p = init || _.modified(Forces, i) ? getForce(f[i])
      : pulse && modified(f[i], pulse) ? sim.force(name)
      : null;
    if (p) sim.force(name, p);
  }

  for (n=(sim.numForces || 0); i<n; ++i) {
    sim.force(Forces + i, null); // remove
  }

  sim.numForces = f.length;
  return sim;
}

function modified(f, pulse) {
  var k, v;
  for (k in f) {
    if (isFunction(v = f[k]) && pulse.modified(accessorFields(v)))
      return 1;
  }
  return 0;
}

function getForce(_) {
  var f, p;

  if (!hasOwnProperty(ForceMap, _.force)) {
    error('Unrecognized force: ' + _.force);
  }
  f = ForceMap[_.force]();

  for (p in _) {
    if (isFunction(f[p])) setForceParam(f[p], _[p], _);
  }

  return f;
}

function setForceParam(f, v, _) {
  f(isFunction(v) ? function(d) { return v(d, _); } : v);
}



var force = /*#__PURE__*/Object.freeze({
  __proto__: null,
  force: Force
});

// Build lookup table mapping tuple keys to tree node instances
function lookup$3(tree, key, filter) {
  var map = {};
  tree.each(function(node) {
    var t = node.data;
    if (filter(t)) map[key(t)] = node;
  });
  tree.lookup = map;
  return tree;
}

/**
  * Nest tuples into a tree structure, grouped by key values.
  * @constructor
  * @param {object} params - The parameters for this operator.
  * @param {Array<function(object): *>} params.keys - The key fields to nest by, in order.
  * @param {boolean} [params.generate=false] - A boolean flag indicating if
  *   non-leaf nodes generated by this transform should be included in the
  *   output. The default (false) includes only the input data (leaf nodes)
  *   in the data stream.
  */
function Nest(params) {
  Transform.call(this, null, params);
}

Nest.Definition = {
  "type": "Nest",
  "metadata": {"treesource": true, "changes": true},
  "params": [
    { "name": "keys", "type": "field", "array": true },
    { "name": "generate", "type": "boolean" }
  ]
};

var prototype$1e = inherits(Nest, Transform);

function children(n) {
  return n.values;
}

prototype$1e.transform = function(_, pulse) {
  if (!pulse.source) {
    error('Nest transform requires an upstream data source.');
  }

  var gen = _.generate,
      mod = _.modified(),
      out = pulse.clone(),
      tree = this.value;

  if (!tree || mod || pulse.changed()) {
    // collect nodes to remove
    if (tree) {
      tree.each(node => {
        if (node.children && isTuple(node.data)) {
          out.rem.push(node.data);
        }
      });
    }

    // generate new tree structure
    this.value = tree = hierarchy({
      values: array(_.keys)
        .reduce((n, k) => { n.key(k); return n; }, nest())
        .entries(out.source)
    }, children);

    // collect nodes to add
    if (gen) {
      tree.each(node => {
        if (node.children) {
          node = ingest(node.data);
          out.add.push(node);
          out.source.push(node);
        }
      });
    }

    // build lookup table
    lookup$3(tree, tupleid, tupleid);
  }

  out.source.root = tree;
  return out;
};

function nest() {
  var keys = [],
      nest;

  function apply(array, depth) {
    if (depth >= keys.length) {
      return array;
    }

    var i = -1,
        n = array.length,
        key = keys[depth++],
        keyValue,
        value,
        valuesByKey = {},
        values,
        result = {};

    while (++i < n) {
      keyValue = key(value = array[i]) + '';
      if (values = valuesByKey[keyValue]) {
        values.push(value);
      } else {
        valuesByKey[keyValue] = [value];
      }
    }

    for (keyValue in valuesByKey) {
      result[keyValue] = apply(valuesByKey[keyValue], depth);
    }

    return result;
  }

  function entries(map, depth) {
    if (++depth > keys.length) return map;
    var array = [], k;
    for (k in map) {
      array.push({key: k, values: entries(map[k], depth)});
    }
    return array;
  }

  return nest = {
    entries: array => entries(apply(array, 0), 0),
    key: d => { keys.push(d); return nest; }
  };
}

/**
 * Abstract class for tree layout.
 * @constructor
 * @param {object} params - The parameters for this operator.
 */
function HierarchyLayout(params) {
  Transform.call(this, null, params);
}

var prototype$1f = inherits(HierarchyLayout, Transform);

prototype$1f.transform = function(_, pulse) {
  if (!pulse.source || !pulse.source.root) {
    error(this.constructor.name
      + ' transform requires a backing tree data source.');
  }

  var layout = this.layout(_.method),
      fields = this.fields,
      root = pulse.source.root,
      as = _.as || fields;

  if (_.field) root.sum(_.field); else root.count();
  if (_.sort) root.sort(stableCompare(_.sort, d => d.data));

  setParams(layout, this.params, _);
  if (layout.separation) {
    layout.separation(_.separation !== false ? defaultSeparation : one);
  }

  try {
    this.value = layout(root);
  } catch (err) {
    error(err);
  }
  root.each(function(node) { setFields(node, fields, as); });

  return pulse.reflow(_.modified()).modifies(as).modifies('leaf');
};

function setParams(layout, params, _) {
  for (var p, i=0, n=params.length; i<n; ++i) {
    p = params[i];
    if (p in _) layout[p](_[p]);
  }
}

function setFields(node, fields, as) {
  var t = node.data;
  for (var i=0, n=fields.length-1; i<n; ++i) {
    t[as[i]] = node[fields[i]];
  }
  t[as[n]] = node.children ? node.children.length : 0;
}

function defaultSeparation(a, b) {
  return a.parent === b.parent ? 1 : 2;
}

var Output$1 = ['x', 'y', 'r', 'depth', 'children'];

/**
 * Packed circle tree layout.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The value field to size nodes.
 */
function Pack(params) {
  HierarchyLayout.call(this, params);
}

Pack.Definition = {
  "type": "Pack",
  "metadata": {"tree": true, "modifies": true},
  "params": [
    { "name": "field", "type": "field" },
    { "name": "sort", "type": "compare" },
    { "name": "padding", "type": "number", "default": 0 },
    { "name": "radius", "type": "field", "default": null },
    { "name": "size", "type": "number", "array": true, "length": 2 },
    { "name": "as", "type": "string", "array": true, "length": Output$1.length, "default": Output$1 }
  ]
};

var prototype$1g = inherits(Pack, HierarchyLayout);

prototype$1g.layout = pack;

prototype$1g.params = ['radius', 'size', 'padding'];

prototype$1g.fields = Output$1;

var Output$2 = ['x0', 'y0', 'x1', 'y1', 'depth', 'children'];

/**
 * Partition tree layout.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The value field to size nodes.
 */
function Partition(params) {
  HierarchyLayout.call(this, params);
}

Partition.Definition = {
  "type": "Partition",
  "metadata": {"tree": true, "modifies": true},
  "params": [
    { "name": "field", "type": "field" },
    { "name": "sort", "type": "compare" },
    { "name": "padding", "type": "number", "default": 0 },
    { "name": "round", "type": "boolean", "default": false },
    { "name": "size", "type": "number", "array": true, "length": 2 },
    { "name": "as", "type": "string", "array": true, "length": Output$2.length, "default": Output$2 }
  ]
};

var prototype$1h = inherits(Partition, HierarchyLayout);

prototype$1h.layout = partition$5;

prototype$1h.params = ['size', 'round', 'padding'];

prototype$1h.fields = Output$2;

/**
  * Stratify a collection of tuples into a tree structure based on
  * id and parent id fields.
  * @constructor
  * @param {object} params - The parameters for this operator.
  * @param {function(object): *} params.key - Unique key field for each tuple.
  * @param {function(object): *} params.parentKey - Field with key for parent tuple.
  */
function Stratify(params) {
  Transform.call(this, null, params);
}

Stratify.Definition = {
  "type": "Stratify",
  "metadata": {"treesource": true},
  "params": [
    { "name": "key", "type": "field", "required": true },
    { "name": "parentKey", "type": "field", "required": true  }
  ]
};

var prototype$1i = inherits(Stratify, Transform);

prototype$1i.transform = function(_, pulse) {
  if (!pulse.source) {
    error('Stratify transform requires an upstream data source.');
  }

  var tree = this.value,
      mod = _.modified(),
      out = pulse.fork(pulse.ALL).materialize(pulse.SOURCE),
      run = !this.value
         || mod
         || pulse.changed(pulse.ADD_REM)
         || pulse.modified(_.key.fields)
         || pulse.modified(_.parentKey.fields);

  // prevent upstream source pollution
  out.source = out.source.slice();

  if (run) {
    if (out.source.length) {
      tree = lookup$3(
        stratify().id(_.key).parentId(_.parentKey)(out.source)
        , _.key, truthy);
    } else {
      tree = lookup$3(stratify()([{}]), _.key, _.key);
    }
  }

  out.source.root = this.value = tree;
  return out;
};

var Layouts = {
  tidy: tree$1,
  cluster: cluster
};

var Output$3 = ['x', 'y', 'depth', 'children'];

/**
 * Tree layout. Depending on the method parameter, performs either
 * Reingold-Tilford 'tidy' layout or dendrogram 'cluster' layout.
 * @constructor
 * @param {object} params - The parameters for this operator.
 */
function Tree(params) {
  HierarchyLayout.call(this, params);
}

Tree.Definition = {
  "type": "Tree",
  "metadata": {"tree": true, "modifies": true},
  "params": [
    { "name": "field", "type": "field" },
    { "name": "sort", "type": "compare" },
    { "name": "method", "type": "enum", "default": "tidy", "values": ["tidy", "cluster"] },
    { "name": "size", "type": "number", "array": true, "length": 2 },
    { "name": "nodeSize", "type": "number", "array": true, "length": 2 },
    { "name": "separation", "type": "boolean", "default": true },
    { "name": "as", "type": "string", "array": true, "length": Output$3.length, "default": Output$3 }
  ]
};

var prototype$1j = inherits(Tree, HierarchyLayout);

/**
 * Tree layout generator. Supports both 'tidy' and 'cluster' layouts.
 */
prototype$1j.layout = function(method) {
  var m = method || 'tidy';
  if (hasOwnProperty(Layouts, m)) return Layouts[m]();
  else error('Unrecognized Tree layout method: ' + m);
};

prototype$1j.params = ['size', 'nodeSize'];

prototype$1j.fields = Output$3;

/**
  * Generate tuples representing links between tree nodes.
  * The resulting tuples will contain 'source' and 'target' fields,
  * which point to parent and child node tuples, respectively.
  * @constructor
  * @param {object} params - The parameters for this operator.
  */
function TreeLinks(params) {
  Transform.call(this, [], params);
}

TreeLinks.Definition = {
  "type": "TreeLinks",
  "metadata": {"tree": true, "generates": true, "changes": true},
  "params": []
};

var prototype$1k = inherits(TreeLinks, Transform);

prototype$1k.transform = function(_, pulse) {
  var links = this.value,
      tree = pulse.source && pulse.source.root,
      out = pulse.fork(pulse.NO_SOURCE),
      lut = {};

  if (!tree) error('TreeLinks transform requires a tree data source.');

  if (pulse.changed(pulse.ADD_REM)) {
    // remove previous links
    out.rem = links;

    // build lookup table of valid tuples
    pulse.visit(pulse.SOURCE, function(t) { lut[tupleid(t)] = 1; });

    // generate links for all edges incident on valid tuples
    tree.each(function(node) {
      var t = node.data,
          p = node.parent && node.parent.data;
      if (p && lut[tupleid(t)] && lut[tupleid(p)]) {
        out.add.push(ingest({source: p, target: t}));
      }
    });
    this.value = out.add;
  }

  else if (pulse.changed(pulse.MOD)) {
    // build lookup table of modified tuples
    pulse.visit(pulse.MOD, function(t) { lut[tupleid(t)] = 1; });

    // gather links incident on modified tuples
    links.forEach(function(link) {
      if (lut[tupleid(link.source)] || lut[tupleid(link.target)]) {
        out.mod.push(link);
      }
    });
  }

  return out;
};

var Tiles = {
  binary: treemapBinary,
  dice: treemapDice,
  slice: treemapSlice,
  slicedice: treemapSliceDice,
  squarify: treemapSquarify,
  resquarify: treemapResquarify
};

var Output$4 = ['x0', 'y0', 'x1', 'y1', 'depth', 'children'];

/**
 * Treemap layout.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.field - The value field to size nodes.
 */
function Treemap(params) {
  HierarchyLayout.call(this, params);
}

Treemap.Definition = {
  "type": "Treemap",
  "metadata": {"tree": true, "modifies": true},
  "params": [
    { "name": "field", "type": "field" },
    { "name": "sort", "type": "compare" },
    { "name": "method", "type": "enum", "default": "squarify",
      "values": ["squarify", "resquarify", "binary", "dice", "slice", "slicedice"] },
    { "name": "padding", "type": "number", "default": 0 },
    { "name": "paddingInner", "type": "number", "default": 0 },
    { "name": "paddingOuter", "type": "number", "default": 0 },
    { "name": "paddingTop", "type": "number", "default": 0 },
    { "name": "paddingRight", "type": "number", "default": 0 },
    { "name": "paddingBottom", "type": "number", "default": 0 },
    { "name": "paddingLeft", "type": "number", "default": 0 },
    { "name": "ratio", "type": "number", "default": 1.618033988749895 },
    { "name": "round", "type": "boolean", "default": false },
    { "name": "size", "type": "number", "array": true, "length": 2 },
    { "name": "as", "type": "string", "array": true, "length": Output$4.length, "default": Output$4 }
  ]
};

var prototype$1l = inherits(Treemap, HierarchyLayout);

/**
 * Treemap layout generator. Adds 'method' and 'ratio' parameters
 * to configure the underlying tile method.
 */
prototype$1l.layout = function() {
  var x = treemap();
  x.ratio = function(_) {
    var t = x.tile();
    if (t.ratio) x.tile(t.ratio(_));
  };
  x.method = function(_) {
    if (hasOwnProperty(Tiles, _)) x.tile(Tiles[_]);
    else error('Unrecognized Treemap layout method: ' + _);
  };
  return x;
};

prototype$1l.params = [
  'method', 'ratio', 'size', 'round',
  'padding', 'paddingInner', 'paddingOuter',
  'paddingTop', 'paddingRight', 'paddingBottom', 'paddingLeft'
];

prototype$1l.fields = Output$4;



var tree = /*#__PURE__*/Object.freeze({
  __proto__: null,
  nest: Nest,
  pack: Pack,
  partition: Partition,
  stratify: Stratify,
  tree: Tree,
  treelinks: TreeLinks,
  treemap: Treemap
});

function partition$4(data, groupby) {
  var groups = [],
      get = function(f) { return f(t); },
      map, i, n, t, k, g;

  // partition data points into stack groups
  if (groupby == null) {
    groups.push(data);
  } else {
    for (map={}, i=0, n=data.length; i<n; ++i) {
      t = data[i];
      k = groupby.map(get);
      g = map[k];
      if (!g) {
        map[k] = (g = []);
        g.dims = k;
        groups.push(g);
      }
      g.push(t);
    }
  }

  return groups;
}

/**
 * Compute locally-weighted regression fits for one or more data groups.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.x - An accessor for the predictor data field.
 * @param {function(object): *} params.y - An accessor for the predicted data field.
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors to groupby.
 * @param {number} [params.bandwidth=0.3] - The loess bandwidth.
 */
function Loess(params) {
  Transform.call(this, null, params);
}

Loess.Definition = {
  "type": "Loess",
  "metadata": {"generates": true},
  "params": [
    { "name": "x", "type": "field", "required": true },
    { "name": "y", "type": "field", "required": true },
    { "name": "groupby", "type": "field", "array": true },
    { "name": "bandwidth", "type": "number", "default": 0.3 },
    { "name": "as", "type": "string", "array": true }
  ]
};

var prototype$1m = inherits(Loess, Transform);

prototype$1m.transform = function(_, pulse) {
  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS);

  if (!this.value || pulse.changed() || _.modified()) {
    const source = pulse.materialize(pulse.SOURCE).source,
          groups = partition$4(source, _.groupby),
          names = (_.groupby || []).map(accessorName),
          m = names.length,
          as = _.as || [accessorName(_.x), accessorName(_.y)],
          values = [];

    groups.forEach(g => {
      regressionLoess(g, _.x, _.y, _.bandwidth || 0.3).forEach(p => {
        const t = {};
        for (let i=0; i<m; ++i) {
          t[names[i]] = g.dims[i];
        }
        t[as[0]] = p[0];
        t[as[1]] = p[1];
        values.push(ingest(t));
      });
    });

    if (this.value) out.rem = this.value;
    this.value = out.add = out.source = values;
  }

  return out;
};

const Methods$1 = {
  linear: regressionLinear,
  log:    regressionLog,
  exp:    regressionExp,
  pow:    regressionPow,
  quad:   regressionQuad,
  poly:   regressionPoly
};

function degreesOfFreedom(method, order) {
  return method === 'poly' ? order : method === 'quad' ? 2 : 1;
}

/**
 * Compute regression fits for one or more data groups.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {function(object): *} params.x - An accessor for the predictor data field.
 * @param {function(object): *} params.y - An accessor for the predicted data field.
 * @param {string} [params.method='linear'] - The regression method to apply.
 * @param {Array<function(object): *>} [params.groupby] - An array of accessors to groupby.
 * @param {Array<number>} [params.extent] - The domain extent over which to plot the regression line.
 * @param {number} [params.order=3] - The polynomial order. Only applies to the 'poly' method.
 */
function Regression(params) {
  Transform.call(this, null, params);
}

Regression.Definition = {
  "type": "Regression",
  "metadata": {"generates": true},
  "params": [
    { "name": "x", "type": "field", "required": true },
    { "name": "y", "type": "field", "required": true },
    { "name": "groupby", "type": "field", "array": true },
    { "name": "method", "type": "string", "default": "linear", "values": Object.keys(Methods$1) },
    { "name": "order", "type": "number", "default": 3 },
    { "name": "extent", "type": "number", "array": true, "length": 2 },
    { "name": "params", "type": "boolean", "default": false },
    { "name": "as", "type": "string", "array": true }
  ]
};

var prototype$1n = inherits(Regression, Transform);

prototype$1n.transform = function(_, pulse) {
  var out = pulse.fork(pulse.NO_SOURCE | pulse.NO_FIELDS);

  if (!this.value || pulse.changed() || _.modified()) {
    const source = pulse.materialize(pulse.SOURCE).source,
          groups = partition$4(source, _.groupby),
          names = (_.groupby || []).map(accessorName),
          method = _.method || 'linear',
          order = _.order || 3,
          dof = degreesOfFreedom(method, order),
          as = _.as || [accessorName(_.x), accessorName(_.y)],
          fit = Methods$1[method],
          values = [];

    let domain = _.extent;

    if (!hasOwnProperty(Methods$1, method)) {
      error('Invalid regression method: ' + method);
    }

    if (domain != null) {
      if (method === 'log' && domain[0] <= 0) {
        pulse.dataflow.warn('Ignoring extent with values <= 0 for log regression.');
        domain = null;
      }
    }

    groups.forEach(g => {
      const n = g.length;
      if (n <= dof) {
        pulse.dataflow.warn('Skipping regression with more parameters than data points.');
        return;
      }

      const model = fit(g, _.x, _.y, order);

      if (_.params) {
        // if parameter vectors requested return those
        values.push(ingest({
          keys: g.dims,
          coef: model.coef,
          rSquared: model.rSquared
        }));
        return;
      }

      const dom = domain || extent(g, _.x),
            add = p => {
              const t = {};
              for (let i=0; i<names.length; ++i) {
                t[names[i]] = g.dims[i];
              }
              t[as[0]] = p[0];
              t[as[1]] = p[1];
              values.push(ingest(t));
            };

      if (method === 'linear') {
        // for linear regression we only need the end points
        dom.forEach(x => add([x, model.predict(x)]));
      } else {
        // otherwise return trend line sample points
        sampleCurve(model.predict, dom, 25, 200).forEach(add);
      }
    });

    if (this.value) out.rem = this.value;
    this.value = out.add = out.source = values;
  }

  return out;
};



var reg = /*#__PURE__*/Object.freeze({
  __proto__: null,
  loess: Loess,
  regression: Regression
});

const EPSILON$2 = Math.pow(2, -52);
const EDGE_STACK = new Uint32Array(512);

class Delaunator {

    static from(points, getX = defaultGetX, getY = defaultGetY) {
        const n = points.length;
        const coords = new Float64Array(n * 2);

        for (let i = 0; i < n; i++) {
            const p = points[i];
            coords[2 * i] = getX(p);
            coords[2 * i + 1] = getY(p);
        }

        return new Delaunator(coords);
    }

    constructor(coords) {
        const n = coords.length >> 1;
        if (n > 0 && typeof coords[0] !== 'number') throw new Error('Expected coords to contain numbers.');

        this.coords = coords;

        // arrays that will store the triangulation graph
        const maxTriangles = Math.max(2 * n - 5, 0);
        this._triangles = new Uint32Array(maxTriangles * 3);
        this._halfedges = new Int32Array(maxTriangles * 3);

        // temporary arrays for tracking the edges of the advancing convex hull
        this._hashSize = Math.ceil(Math.sqrt(n));
        this._hullPrev = new Uint32Array(n); // edge to prev edge
        this._hullNext = new Uint32Array(n); // edge to next edge
        this._hullTri = new Uint32Array(n); // edge to adjacent triangle
        this._hullHash = new Int32Array(this._hashSize).fill(-1); // angular edge hash

        // temporary arrays for sorting points
        this._ids = new Uint32Array(n);
        this._dists = new Float64Array(n);

        this.update();
    }

    update() {
        const {coords, _hullPrev: hullPrev, _hullNext: hullNext, _hullTri: hullTri, _hullHash: hullHash} =  this;
        const n = coords.length >> 1;

        // populate an array of point indices; calculate input data bbox
        let minX = Infinity;
        let minY = Infinity;
        let maxX = -Infinity;
        let maxY = -Infinity;

        for (let i = 0; i < n; i++) {
            const x = coords[2 * i];
            const y = coords[2 * i + 1];
            if (x < minX) minX = x;
            if (y < minY) minY = y;
            if (x > maxX) maxX = x;
            if (y > maxY) maxY = y;
            this._ids[i] = i;
        }
        const cx = (minX + maxX) / 2;
        const cy = (minY + maxY) / 2;

        let minDist = Infinity;
        let i0, i1, i2;

        // pick a seed point close to the center
        for (let i = 0; i < n; i++) {
            const d = dist(cx, cy, coords[2 * i], coords[2 * i + 1]);
            if (d < minDist) {
                i0 = i;
                minDist = d;
            }
        }
        const i0x = coords[2 * i0];
        const i0y = coords[2 * i0 + 1];

        minDist = Infinity;

        // find the point closest to the seed
        for (let i = 0; i < n; i++) {
            if (i === i0) continue;
            const d = dist(i0x, i0y, coords[2 * i], coords[2 * i + 1]);
            if (d < minDist && d > 0) {
                i1 = i;
                minDist = d;
            }
        }
        let i1x = coords[2 * i1];
        let i1y = coords[2 * i1 + 1];

        let minRadius = Infinity;

        // find the third point which forms the smallest circumcircle with the first two
        for (let i = 0; i < n; i++) {
            if (i === i0 || i === i1) continue;
            const r = circumradius(i0x, i0y, i1x, i1y, coords[2 * i], coords[2 * i + 1]);
            if (r < minRadius) {
                i2 = i;
                minRadius = r;
            }
        }
        let i2x = coords[2 * i2];
        let i2y = coords[2 * i2 + 1];

        if (minRadius === Infinity) {
            // order collinear points by dx (or dy if all x are identical)
            // and return the list as a hull
            for (let i = 0; i < n; i++) {
                this._dists[i] = (coords[2 * i] - coords[0]) || (coords[2 * i + 1] - coords[1]);
            }
            quicksort(this._ids, this._dists, 0, n - 1);
            const hull = new Uint32Array(n);
            let j = 0;
            for (let i = 0, d0 = -Infinity; i < n; i++) {
                const id = this._ids[i];
                if (this._dists[id] > d0) {
                    hull[j++] = id;
                    d0 = this._dists[id];
                }
            }
            this.hull = hull.subarray(0, j);
            this.triangles = new Uint32Array(0);
            this.halfedges = new Uint32Array(0);
            return;
        }

        // swap the order of the seed points for counter-clockwise orientation
        if (orient(i0x, i0y, i1x, i1y, i2x, i2y)) {
            const i = i1;
            const x = i1x;
            const y = i1y;
            i1 = i2;
            i1x = i2x;
            i1y = i2y;
            i2 = i;
            i2x = x;
            i2y = y;
        }

        const center = circumcenter(i0x, i0y, i1x, i1y, i2x, i2y);
        this._cx = center.x;
        this._cy = center.y;

        for (let i = 0; i < n; i++) {
            this._dists[i] = dist(coords[2 * i], coords[2 * i + 1], center.x, center.y);
        }

        // sort the points by distance from the seed triangle circumcenter
        quicksort(this._ids, this._dists, 0, n - 1);

        // set up the seed triangle as the starting hull
        this._hullStart = i0;
        let hullSize = 3;

        hullNext[i0] = hullPrev[i2] = i1;
        hullNext[i1] = hullPrev[i0] = i2;
        hullNext[i2] = hullPrev[i1] = i0;

        hullTri[i0] = 0;
        hullTri[i1] = 1;
        hullTri[i2] = 2;

        hullHash.fill(-1);
        hullHash[this._hashKey(i0x, i0y)] = i0;
        hullHash[this._hashKey(i1x, i1y)] = i1;
        hullHash[this._hashKey(i2x, i2y)] = i2;

        this.trianglesLen = 0;
        this._addTriangle(i0, i1, i2, -1, -1, -1);

        for (let k = 0, xp, yp; k < this._ids.length; k++) {
            const i = this._ids[k];
            const x = coords[2 * i];
            const y = coords[2 * i + 1];

            // skip near-duplicate points
            if (k > 0 && Math.abs(x - xp) <= EPSILON$2 && Math.abs(y - yp) <= EPSILON$2) continue;
            xp = x;
            yp = y;

            // skip seed triangle points
            if (i === i0 || i === i1 || i === i2) continue;

            // find a visible edge on the convex hull using edge hash
            let start = 0;
            for (let j = 0, key = this._hashKey(x, y); j < this._hashSize; j++) {
                start = hullHash[(key + j) % this._hashSize];
                if (start !== -1 && start !== hullNext[start]) break;
            }

            start = hullPrev[start];
            let e = start, q;
            while (q = hullNext[e], !orient(x, y, coords[2 * e], coords[2 * e + 1], coords[2 * q], coords[2 * q + 1])) {
                e = q;
                if (e === start) {
                    e = -1;
                    break;
                }
            }
            if (e === -1) continue; // likely a near-duplicate point; skip it

            // add the first triangle from the point
            let t = this._addTriangle(e, i, hullNext[e], -1, -1, hullTri[e]);

            // recursively flip triangles from the point until they satisfy the Delaunay condition
            hullTri[i] = this._legalize(t + 2);
            hullTri[e] = t; // keep track of boundary triangles on the hull
            hullSize++;

            // walk forward through the hull, adding more triangles and flipping recursively
            let n = hullNext[e];
            while (q = hullNext[n], orient(x, y, coords[2 * n], coords[2 * n + 1], coords[2 * q], coords[2 * q + 1])) {
                t = this._addTriangle(n, i, q, hullTri[i], -1, hullTri[n]);
                hullTri[i] = this._legalize(t + 2);
                hullNext[n] = n; // mark as removed
                hullSize--;
                n = q;
            }

            // walk backward from the other side, adding more triangles and flipping
            if (e === start) {
                while (q = hullPrev[e], orient(x, y, coords[2 * q], coords[2 * q + 1], coords[2 * e], coords[2 * e + 1])) {
                    t = this._addTriangle(q, i, e, -1, hullTri[e], hullTri[q]);
                    this._legalize(t + 2);
                    hullTri[q] = t;
                    hullNext[e] = e; // mark as removed
                    hullSize--;
                    e = q;
                }
            }

            // update the hull indices
            this._hullStart = hullPrev[i] = e;
            hullNext[e] = hullPrev[n] = i;
            hullNext[i] = n;

            // save the two new edges in the hash table
            hullHash[this._hashKey(x, y)] = i;
            hullHash[this._hashKey(coords[2 * e], coords[2 * e + 1])] = e;
        }

        this.hull = new Uint32Array(hullSize);
        for (let i = 0, e = this._hullStart; i < hullSize; i++) {
            this.hull[i] = e;
            e = hullNext[e];
        }

        // trim typed triangle mesh arrays
        this.triangles = this._triangles.subarray(0, this.trianglesLen);
        this.halfedges = this._halfedges.subarray(0, this.trianglesLen);
    }

    _hashKey(x, y) {
        return Math.floor(pseudoAngle(x - this._cx, y - this._cy) * this._hashSize) % this._hashSize;
    }

    _legalize(a) {
        const {_triangles: triangles, _halfedges: halfedges, coords} = this;

        let i = 0;
        let ar = 0;

        // recursion eliminated with a fixed-size stack
        while (true) {
            const b = halfedges[a];

            /* if the pair of triangles doesn't satisfy the Delaunay condition
             * (p1 is inside the circumcircle of [p0, pl, pr]), flip them,
             * then do the same check/flip recursively for the new pair of triangles
             *
             *           pl                    pl
             *          /||\                  /  \
             *       al/ || \bl            al/    \a
             *        /  ||  \              /      \
             *       /  a||b  \    flip    /___ar___\
             *     p0\   ||   /p1   =>   p0\---bl---/p1
             *        \  ||  /              \      /
             *       ar\ || /br             b\    /br
             *          \||/                  \  /
             *           pr                    pr
             */
            const a0 = a - a % 3;
            ar = a0 + (a + 2) % 3;

            if (b === -1) { // convex hull edge
                if (i === 0) break;
                a = EDGE_STACK[--i];
                continue;
            }

            const b0 = b - b % 3;
            const al = a0 + (a + 1) % 3;
            const bl = b0 + (b + 2) % 3;

            const p0 = triangles[ar];
            const pr = triangles[a];
            const pl = triangles[al];
            const p1 = triangles[bl];

            const illegal = inCircle(
                coords[2 * p0], coords[2 * p0 + 1],
                coords[2 * pr], coords[2 * pr + 1],
                coords[2 * pl], coords[2 * pl + 1],
                coords[2 * p1], coords[2 * p1 + 1]);

            if (illegal) {
                triangles[a] = p1;
                triangles[b] = p0;

                const hbl = halfedges[bl];

                // edge swapped on the other side of the hull (rare); fix the halfedge reference
                if (hbl === -1) {
                    let e = this._hullStart;
                    do {
                        if (this._hullTri[e] === bl) {
                            this._hullTri[e] = a;
                            break;
                        }
                        e = this._hullPrev[e];
                    } while (e !== this._hullStart);
                }
                this._link(a, hbl);
                this._link(b, halfedges[ar]);
                this._link(ar, bl);

                const br = b0 + (b + 1) % 3;

                // don't worry about hitting the cap: it can only happen on extremely degenerate input
                if (i < EDGE_STACK.length) {
                    EDGE_STACK[i++] = br;
                }
            } else {
                if (i === 0) break;
                a = EDGE_STACK[--i];
            }
        }

        return ar;
    }

    _link(a, b) {
        this._halfedges[a] = b;
        if (b !== -1) this._halfedges[b] = a;
    }

    // add a new triangle given vertex indices and adjacent half-edge ids
    _addTriangle(i0, i1, i2, a, b, c) {
        const t = this.trianglesLen;

        this._triangles[t] = i0;
        this._triangles[t + 1] = i1;
        this._triangles[t + 2] = i2;

        this._link(t, a);
        this._link(t + 1, b);
        this._link(t + 2, c);

        this.trianglesLen += 3;

        return t;
    }
}

// monotonically increases with real angle, but doesn't need expensive trigonometry
function pseudoAngle(dx, dy) {
    const p = dx / (Math.abs(dx) + Math.abs(dy));
    return (dy > 0 ? 3 - p : 1 + p) / 4; // [0..1]
}

function dist(ax, ay, bx, by) {
    const dx = ax - bx;
    const dy = ay - by;
    return dx * dx + dy * dy;
}

// return 2d orientation sign if we're confident in it through J. Shewchuk's error bound check
function orientIfSure(px, py, rx, ry, qx, qy) {
    const l = (ry - py) * (qx - px);
    const r = (rx - px) * (qy - py);
    return Math.abs(l - r) >= 3.3306690738754716e-16 * Math.abs(l + r) ? l - r : 0;
}

// a more robust orientation test that's stable in a given triangle (to fix robustness issues)
function orient(rx, ry, qx, qy, px, py) {
    const sign = orientIfSure(px, py, rx, ry, qx, qy) ||
    orientIfSure(rx, ry, qx, qy, px, py) ||
    orientIfSure(qx, qy, px, py, rx, ry);
    return sign < 0;
}

function inCircle(ax, ay, bx, by, cx, cy, px, py) {
    const dx = ax - px;
    const dy = ay - py;
    const ex = bx - px;
    const ey = by - py;
    const fx = cx - px;
    const fy = cy - py;

    const ap = dx * dx + dy * dy;
    const bp = ex * ex + ey * ey;
    const cp = fx * fx + fy * fy;

    return dx * (ey * cp - bp * fy) -
           dy * (ex * cp - bp * fx) +
           ap * (ex * fy - ey * fx) < 0;
}

function circumradius(ax, ay, bx, by, cx, cy) {
    const dx = bx - ax;
    const dy = by - ay;
    const ex = cx - ax;
    const ey = cy - ay;

    const bl = dx * dx + dy * dy;
    const cl = ex * ex + ey * ey;
    const d = 0.5 / (dx * ey - dy * ex);

    const x = (ey * bl - dy * cl) * d;
    const y = (dx * cl - ex * bl) * d;

    return x * x + y * y;
}

function circumcenter(ax, ay, bx, by, cx, cy) {
    const dx = bx - ax;
    const dy = by - ay;
    const ex = cx - ax;
    const ey = cy - ay;

    const bl = dx * dx + dy * dy;
    const cl = ex * ex + ey * ey;
    const d = 0.5 / (dx * ey - dy * ex);

    const x = ax + (ey * bl - dy * cl) * d;
    const y = ay + (dx * cl - ex * bl) * d;

    return {x, y};
}

function quicksort(ids, dists, left, right) {
    if (right - left <= 20) {
        for (let i = left + 1; i <= right; i++) {
            const temp = ids[i];
            const tempDist = dists[temp];
            let j = i - 1;
            while (j >= left && dists[ids[j]] > tempDist) ids[j + 1] = ids[j--];
            ids[j + 1] = temp;
        }
    } else {
        const median = (left + right) >> 1;
        let i = left + 1;
        let j = right;
        swap$1(ids, median, i);
        if (dists[ids[left]] > dists[ids[right]]) swap$1(ids, left, right);
        if (dists[ids[i]] > dists[ids[right]]) swap$1(ids, i, right);
        if (dists[ids[left]] > dists[ids[i]]) swap$1(ids, left, i);

        const temp = ids[i];
        const tempDist = dists[temp];
        while (true) {
            do i++; while (dists[ids[i]] < tempDist);
            do j--; while (dists[ids[j]] > tempDist);
            if (j < i) break;
            swap$1(ids, i, j);
        }
        ids[left + 1] = ids[j];
        ids[j] = temp;

        if (right - i + 1 >= j - left) {
            quicksort(ids, dists, i, right);
            quicksort(ids, dists, left, j - 1);
        } else {
            quicksort(ids, dists, left, j - 1);
            quicksort(ids, dists, i, right);
        }
    }
}

function swap$1(arr, i, j) {
    const tmp = arr[i];
    arr[i] = arr[j];
    arr[j] = tmp;
}

function defaultGetX(p) {
    return p[0];
}
function defaultGetY(p) {
    return p[1];
}

const epsilon$2 = 1e-6;

class Path {
  constructor() {
    this._x0 = this._y0 = // start of current subpath
    this._x1 = this._y1 = null; // end of current subpath
    this._ = "";
  }
  moveTo(x, y) {
    this._ += `M${this._x0 = this._x1 = +x},${this._y0 = this._y1 = +y}`;
  }
  closePath() {
    if (this._x1 !== null) {
      this._x1 = this._x0, this._y1 = this._y0;
      this._ += "Z";
    }
  }
  lineTo(x, y) {
    this._ += `L${this._x1 = +x},${this._y1 = +y}`;
  }
  arc(x, y, r) {
    x = +x, y = +y, r = +r;
    const x0 = x + r;
    const y0 = y;
    if (r < 0) throw new Error("negative radius");
    if (this._x1 === null) this._ += `M${x0},${y0}`;
    else if (Math.abs(this._x1 - x0) > epsilon$2 || Math.abs(this._y1 - y0) > epsilon$2) this._ += "L" + x0 + "," + y0;
    if (!r) return;
    this._ += `A${r},${r},0,1,1,${x - r},${y}A${r},${r},0,1,1,${this._x1 = x0},${this._y1 = y0}`;
  }
  rect(x, y, w, h) {
    this._ += `M${this._x0 = this._x1 = +x},${this._y0 = this._y1 = +y}h${+w}v${+h}h${-w}Z`;
  }
  value() {
    return this._ || null;
  }
}

class Polygon {
  constructor() {
    this._ = [];
  }
  moveTo(x, y) {
    this._.push([x, y]);
  }
  closePath() {
    this._.push(this._[0].slice());
  }
  lineTo(x, y) {
    this._.push([x, y]);
  }
  value() {
    return this._.length ? this._ : null;
  }
}

class Voronoi {
  constructor(delaunay, [xmin, ymin, xmax, ymax] = [0, 0, 960, 500]) {
    if (!((xmax = +xmax) >= (xmin = +xmin)) || !((ymax = +ymax) >= (ymin = +ymin))) throw new Error("invalid bounds");
    this.delaunay = delaunay;
    this._circumcenters = new Float64Array(delaunay.points.length * 2);
    this.vectors = new Float64Array(delaunay.points.length * 2);
    this.xmax = xmax, this.xmin = xmin;
    this.ymax = ymax, this.ymin = ymin;
    this._init();
  }
  update() {
    this.delaunay.update();
    this._init();
    return this;
  }
  _init() {
    const {delaunay: {points, hull, triangles}, vectors} = this;

    // Compute circumcenters.
    const circumcenters = this.circumcenters = this._circumcenters.subarray(0, triangles.length / 3 * 2);
    for (let i = 0, j = 0, n = triangles.length, x, y; i < n; i += 3, j += 2) {
      const t1 = triangles[i] * 2;
      const t2 = triangles[i + 1] * 2;
      const t3 = triangles[i + 2] * 2;
      const x1 = points[t1];
      const y1 = points[t1 + 1];
      const x2 = points[t2];
      const y2 = points[t2 + 1];
      const x3 = points[t3];
      const y3 = points[t3 + 1];

      const dx = x2 - x1;
      const dy = y2 - y1;
      const ex = x3 - x1;
      const ey = y3 - y1;
      const bl = dx * dx + dy * dy;
      const cl = ex * ex + ey * ey;
      const ab = (dx * ey - dy * ex) * 2;

      if (!ab) {
        // degenerate case (collinear diagram)
        x = (x1 + x3) / 2 - 1e8 * ey;
        y = (y1 + y3) / 2 + 1e8 * ex;
      }
      else if (Math.abs(ab) < 1e-8) {
        // almost equal points (degenerate triangle)
        x = (x1 + x3) / 2;
        y = (y1 + y3) / 2;
      } else {
        const d = 1 / ab;
        x = x1 + (ey * bl - dy * cl) * d;
        y = y1 + (dx * cl - ex * bl) * d;
      }
      circumcenters[j] = x;
      circumcenters[j + 1] = y;
    }

    // Compute exterior cell rays.
    let h = hull[hull.length - 1];
    let p0, p1 = h * 4;
    let x0, x1 = points[2 * h];
    let y0, y1 = points[2 * h + 1];
    vectors.fill(0);
    for (let i = 0; i < hull.length; ++i) {
      h = hull[i];
      p0 = p1, x0 = x1, y0 = y1;
      p1 = h * 4, x1 = points[2 * h], y1 = points[2 * h + 1];
      vectors[p0 + 2] = vectors[p1] = y0 - y1;
      vectors[p0 + 3] = vectors[p1 + 1] = x1 - x0;
    }
  }
  render(context) {
    const buffer = context == null ? context = new Path : undefined;
    const {delaunay: {halfedges, inedges, hull}, circumcenters, vectors} = this;
    if (hull.length <= 1) return null;
    for (let i = 0, n = halfedges.length; i < n; ++i) {
      const j = halfedges[i];
      if (j < i) continue;
      const ti = Math.floor(i / 3) * 2;
      const tj = Math.floor(j / 3) * 2;
      const xi = circumcenters[ti];
      const yi = circumcenters[ti + 1];
      const xj = circumcenters[tj];
      const yj = circumcenters[tj + 1];
      this._renderSegment(xi, yi, xj, yj, context);
    }
    let h0, h1 = hull[hull.length - 1];
    for (let i = 0; i < hull.length; ++i) {
      h0 = h1, h1 = hull[i];
      const t = Math.floor(inedges[h1] / 3) * 2;
      const x = circumcenters[t];
      const y = circumcenters[t + 1];
      const v = h0 * 4;
      const p = this._project(x, y, vectors[v + 2], vectors[v + 3]);
      if (p) this._renderSegment(x, y, p[0], p[1], context);
    }
    return buffer && buffer.value();
  }
  renderBounds(context) {
    const buffer = context == null ? context = new Path : undefined;
    context.rect(this.xmin, this.ymin, this.xmax - this.xmin, this.ymax - this.ymin);
    return buffer && buffer.value();
  }
  renderCell(i, context) {
    const buffer = context == null ? context = new Path : undefined;
    const points = this._clip(i);
    if (points === null) return;
    context.moveTo(points[0], points[1]);
    let n = points.length;
    while (points[0] === points[n-2] && points[1] === points[n-1] && n > 1) n -= 2;
    for (let i = 2; i < n; i += 2) {
      if (points[i] !== points[i-2] || points[i+1] !== points[i-1])
        context.lineTo(points[i], points[i + 1]);
    }
    context.closePath();
    return buffer && buffer.value();
  }
  *cellPolygons() {
    const {delaunay: {points}} = this;
    for (let i = 0, n = points.length / 2; i < n; ++i) {
      const cell = this.cellPolygon(i);
      if (cell) yield cell;
    }
  }
  cellPolygon(i) {
    const polygon = new Polygon;
    this.renderCell(i, polygon);
    return polygon.value();
  }
  _renderSegment(x0, y0, x1, y1, context) {
    let S;
    const c0 = this._regioncode(x0, y0);
    const c1 = this._regioncode(x1, y1);
    if (c0 === 0 && c1 === 0) {
      context.moveTo(x0, y0);
      context.lineTo(x1, y1);
    } else if (S = this._clipSegment(x0, y0, x1, y1, c0, c1)) {
      context.moveTo(S[0], S[1]);
      context.lineTo(S[2], S[3]);
    }
  }
  contains(i, x, y) {
    if ((x = +x, x !== x) || (y = +y, y !== y)) return false;
    return this.delaunay._step(i, x, y) === i;
  }
  _cell(i) {
    const {circumcenters, delaunay: {inedges, halfedges, triangles}} = this;
    const e0 = inedges[i];
    if (e0 === -1) return null; // coincident point
    const points = [];
    let e = e0;
    do {
      const t = Math.floor(e / 3);
      points.push(circumcenters[t * 2], circumcenters[t * 2 + 1]);
      e = e % 3 === 2 ? e - 2 : e + 1;
      if (triangles[e] !== i) break; // bad triangulation
      e = halfedges[e];
    } while (e !== e0 && e !== -1);
    return points;
  }
  _clip(i) {
    // degenerate case (1 valid point: return the box)
    if (i === 0 && this.delaunay.hull.length === 1) {
      return [this.xmax, this.ymin, this.xmax, this.ymax, this.xmin, this.ymax, this.xmin, this.ymin];
    }
    const points = this._cell(i);
    if (points === null) return null;
    const {vectors: V} = this;
    const v = i * 4;
    return V[v] || V[v + 1]
        ? this._clipInfinite(i, points, V[v], V[v + 1], V[v + 2], V[v + 3])
        : this._clipFinite(i, points);
  }
  _clipFinite(i, points) {
    const n = points.length;
    let P = null;
    let x0, y0, x1 = points[n - 2], y1 = points[n - 1];
    let c0, c1 = this._regioncode(x1, y1);
    let e0, e1;
    for (let j = 0; j < n; j += 2) {
      x0 = x1, y0 = y1, x1 = points[j], y1 = points[j + 1];
      c0 = c1, c1 = this._regioncode(x1, y1);
      if (c0 === 0 && c1 === 0) {
        e0 = e1, e1 = 0;
        if (P) P.push(x1, y1);
        else P = [x1, y1];
      } else {
        let S, sx0, sy0, sx1, sy1;
        if (c0 === 0) {
          if ((S = this._clipSegment(x0, y0, x1, y1, c0, c1)) === null) continue;
          [sx0, sy0, sx1, sy1] = S;
        } else {
          if ((S = this._clipSegment(x1, y1, x0, y0, c1, c0)) === null) continue;
          [sx1, sy1, sx0, sy0] = S;
          e0 = e1, e1 = this._edgecode(sx0, sy0);
          if (e0 && e1) this._edge(i, e0, e1, P, P.length);
          if (P) P.push(sx0, sy0);
          else P = [sx0, sy0];
        }
        e0 = e1, e1 = this._edgecode(sx1, sy1);
        if (e0 && e1) this._edge(i, e0, e1, P, P.length);
        if (P) P.push(sx1, sy1);
        else P = [sx1, sy1];
      }
    }
    if (P) {
      e0 = e1, e1 = this._edgecode(P[0], P[1]);
      if (e0 && e1) this._edge(i, e0, e1, P, P.length);
    } else if (this.contains(i, (this.xmin + this.xmax) / 2, (this.ymin + this.ymax) / 2)) {
      return [this.xmax, this.ymin, this.xmax, this.ymax, this.xmin, this.ymax, this.xmin, this.ymin];
    }
    return P;
  }
  _clipSegment(x0, y0, x1, y1, c0, c1) {
    while (true) {
      if (c0 === 0 && c1 === 0) return [x0, y0, x1, y1];
      if (c0 & c1) return null;
      let x, y, c = c0 || c1;
      if (c & 0b1000) x = x0 + (x1 - x0) * (this.ymax - y0) / (y1 - y0), y = this.ymax;
      else if (c & 0b0100) x = x0 + (x1 - x0) * (this.ymin - y0) / (y1 - y0), y = this.ymin;
      else if (c & 0b0010) y = y0 + (y1 - y0) * (this.xmax - x0) / (x1 - x0), x = this.xmax;
      else y = y0 + (y1 - y0) * (this.xmin - x0) / (x1 - x0), x = this.xmin;
      if (c0) x0 = x, y0 = y, c0 = this._regioncode(x0, y0);
      else x1 = x, y1 = y, c1 = this._regioncode(x1, y1);
    }
  }
  _clipInfinite(i, points, vx0, vy0, vxn, vyn) {
    let P = Array.from(points), p;
    if (p = this._project(P[0], P[1], vx0, vy0)) P.unshift(p[0], p[1]);
    if (p = this._project(P[P.length - 2], P[P.length - 1], vxn, vyn)) P.push(p[0], p[1]);
    if (P = this._clipFinite(i, P)) {
      for (let j = 0, n = P.length, c0, c1 = this._edgecode(P[n - 2], P[n - 1]); j < n; j += 2) {
        c0 = c1, c1 = this._edgecode(P[j], P[j + 1]);
        if (c0 && c1) j = this._edge(i, c0, c1, P, j), n = P.length;
      }
    } else if (this.contains(i, (this.xmin + this.xmax) / 2, (this.ymin + this.ymax) / 2)) {
      P = [this.xmin, this.ymin, this.xmax, this.ymin, this.xmax, this.ymax, this.xmin, this.ymax];
    }
    return P;
  }
  _edge(i, e0, e1, P, j) {
    while (e0 !== e1) {
      let x, y;
      switch (e0) {
        case 0b0101: e0 = 0b0100; continue; // top-left
        case 0b0100: e0 = 0b0110, x = this.xmax, y = this.ymin; break; // top
        case 0b0110: e0 = 0b0010; continue; // top-right
        case 0b0010: e0 = 0b1010, x = this.xmax, y = this.ymax; break; // right
        case 0b1010: e0 = 0b1000; continue; // bottom-right
        case 0b1000: e0 = 0b1001, x = this.xmin, y = this.ymax; break; // bottom
        case 0b1001: e0 = 0b0001; continue; // bottom-left
        case 0b0001: e0 = 0b0101, x = this.xmin, y = this.ymin; break; // left
      }
      if ((P[j] !== x || P[j + 1] !== y) && this.contains(i, x, y)) {
        P.splice(j, 0, x, y), j += 2;
      }
    }
    if (P.length > 4) {
      for (let i = 0; i < P.length; i+= 2) {
        const j = (i + 2) % P.length, k = (i + 4) % P.length;
        if (P[i] === P[j] && P[j] === P[k]
        || P[i + 1] === P[j + 1] && P[j + 1] === P[k + 1])
          P.splice(j, 2), i -= 2;
      }
    }
    return j;
  }
  _project(x0, y0, vx, vy) {
    let t = Infinity, c, x, y;
    if (vy < 0) { // top
      if (y0 <= this.ymin) return null;
      if ((c = (this.ymin - y0) / vy) < t) y = this.ymin, x = x0 + (t = c) * vx;
    } else if (vy > 0) { // bottom
      if (y0 >= this.ymax) return null;
      if ((c = (this.ymax - y0) / vy) < t) y = this.ymax, x = x0 + (t = c) * vx;
    }
    if (vx > 0) { // right
      if (x0 >= this.xmax) return null;
      if ((c = (this.xmax - x0) / vx) < t) x = this.xmax, y = y0 + (t = c) * vy;
    } else if (vx < 0) { // left
      if (x0 <= this.xmin) return null;
      if ((c = (this.xmin - x0) / vx) < t) x = this.xmin, y = y0 + (t = c) * vy;
    }
    return [x, y];
  }
  _edgecode(x, y) {
    return (x === this.xmin ? 0b0001
        : x === this.xmax ? 0b0010 : 0b0000)
        | (y === this.ymin ? 0b0100
        : y === this.ymax ? 0b1000 : 0b0000);
  }
  _regioncode(x, y) {
    return (x < this.xmin ? 0b0001
        : x > this.xmax ? 0b0010 : 0b0000)
        | (y < this.ymin ? 0b0100
        : y > this.ymax ? 0b1000 : 0b0000);
  }
}

const tau = 2 * Math.PI;

function pointX(p) {
  return p[0];
}

function pointY(p) {
  return p[1];
}

// A triangulation is collinear if all its triangles have a non-null area
function collinear$1(d) {
  const {triangles, coords} = d;
  for (let i = 0; i < triangles.length; i += 3) {
    const a = 2 * triangles[i],
          b = 2 * triangles[i + 1],
          c = 2 * triangles[i + 2],
          cross = (coords[c] - coords[a]) * (coords[b + 1] - coords[a + 1])
                - (coords[b] - coords[a]) * (coords[c + 1] - coords[a + 1]);
    if (cross > 1e-10) return false;
  }
  return true;
}

function jitter(x, y, r) {
  return [x + Math.sin(x + y) * r, y + Math.cos(x - y) * r];
}

class Delaunay {
  constructor(points) {
    this._delaunator = new Delaunator(points);
    this.inedges = new Int32Array(points.length / 2);
    this._hullIndex = new Int32Array(points.length / 2);
    this.points = this._delaunator.coords;
    this._init();
  }
  update() {
    this._delaunator.update();
    this._init();
    return this;
  }
  _init() {
    const d = this._delaunator, points = this.points;

    // check for collinear
    if (d.hull && d.hull.length > 2 && collinear$1(d)) {
      this.collinear = Int32Array.from({length: points.length/2}, (_,i) => i)
        .sort((i, j) => points[2 * i] - points[2 * j] || points[2 * i + 1] - points[2 * j + 1]); // for exact neighbors
      const e = this.collinear[0], f = this.collinear[this.collinear.length - 1],
        bounds = [ points[2 * e], points[2 * e + 1], points[2 * f], points[2 * f + 1] ],
        r = 1e-8 * Math.sqrt((bounds[3] - bounds[1])**2 + (bounds[2] - bounds[0])**2);
      for (let i = 0, n = points.length / 2; i < n; ++i) {
        const p = jitter(points[2 * i], points[2 * i + 1], r);
        points[2 * i] = p[0];
        points[2 * i + 1] = p[1];
      }
      this._delaunator = new Delaunator(points);
    } else {
      delete this.collinear;
    }

    const halfedges = this.halfedges = this._delaunator.halfedges;
    const hull = this.hull = this._delaunator.hull;
    const triangles = this.triangles = this._delaunator.triangles;
    const inedges = this.inedges.fill(-1);
    const hullIndex = this._hullIndex.fill(-1);

    // Compute an index from each point to an (arbitrary) incoming halfedge
    // Used to give the first neighbor of each point; for this reason,
    // on the hull we give priority to exterior halfedges
    for (let e = 0, n = halfedges.length; e < n; ++e) {
      const p = triangles[e % 3 === 2 ? e - 2 : e + 1];
      if (halfedges[e] === -1 || inedges[p] === -1) inedges[p] = e;
    }
    for (let i = 0, n = hull.length; i < n; ++i) {
      hullIndex[hull[i]] = i;
    }

    // degenerate case: 1 or 2 (distinct) points
    if (hull.length <= 2 && hull.length > 0) {
      this.triangles = new Int32Array(3).fill(-1);
      this.halfedges = new Int32Array(3).fill(-1);
      this.triangles[0] = hull[0];
      this.triangles[1] = hull[1];
      this.triangles[2] = hull[1];
      inedges[hull[0]] = 1;
      if (hull.length === 2) inedges[hull[1]] = 0;
    }
  }
  voronoi(bounds) {
    return new Voronoi(this, bounds);
  }
  *neighbors(i) {
    const {inedges, hull, _hullIndex, halfedges, triangles} = this;

    // degenerate case with several collinear points
    if (this.collinear) {
      const l = this.collinear.indexOf(i);
      if (l > 0) yield this.collinear[l - 1];
      if (l < this.collinear.length - 1) yield this.collinear[l + 1];
      return;
    }

    const e0 = inedges[i];
    if (e0 === -1) return; // coincident point
    let e = e0, p0 = -1;
    do {
      yield p0 = triangles[e];
      e = e % 3 === 2 ? e - 2 : e + 1;
      if (triangles[e] !== i) return; // bad triangulation
      e = halfedges[e];
      if (e === -1) {
        const p = hull[(_hullIndex[i] + 1) % hull.length];
        if (p !== p0) yield p;
        return;
      }
    } while (e !== e0);
  }
  find(x, y, i = 0) {
    if ((x = +x, x !== x) || (y = +y, y !== y)) return -1;
    const i0 = i;
    let c;
    while ((c = this._step(i, x, y)) >= 0 && c !== i && c !== i0) i = c;
    return c;
  }
  _step(i, x, y) {
    const {inedges, hull, _hullIndex, halfedges, triangles, points} = this;
    if (inedges[i] === -1 || !points.length) return (i + 1) % (points.length >> 1);
    let c = i;
    let dc = (x - points[i * 2]) ** 2 + (y - points[i * 2 + 1]) ** 2;
    const e0 = inedges[i];
    let e = e0;
    do {
      let t = triangles[e];
      const dt = (x - points[t * 2]) ** 2 + (y - points[t * 2 + 1]) ** 2;
      if (dt < dc) dc = dt, c = t;
      e = e % 3 === 2 ? e - 2 : e + 1;
      if (triangles[e] !== i) break; // bad triangulation
      e = halfedges[e];
      if (e === -1) {
        e = hull[(_hullIndex[i] + 1) % hull.length];
        if (e !== t) {
          if ((x - points[e * 2]) ** 2 + (y - points[e * 2 + 1]) ** 2 < dc) return e;
        }
        break;
      }
    } while (e !== e0);
    return c;
  }
  render(context) {
    const buffer = context == null ? context = new Path : undefined;
    const {points, halfedges, triangles} = this;
    for (let i = 0, n = halfedges.length; i < n; ++i) {
      const j = halfedges[i];
      if (j < i) continue;
      const ti = triangles[i] * 2;
      const tj = triangles[j] * 2;
      context.moveTo(points[ti], points[ti + 1]);
      context.lineTo(points[tj], points[tj + 1]);
    }
    this.renderHull(context);
    return buffer && buffer.value();
  }
  renderPoints(context, r = 2) {
    const buffer = context == null ? context = new Path : undefined;
    const {points} = this;
    for (let i = 0, n = points.length; i < n; i += 2) {
      const x = points[i], y = points[i + 1];
      context.moveTo(x + r, y);
      context.arc(x, y, r, 0, tau);
    }
    return buffer && buffer.value();
  }
  renderHull(context) {
    const buffer = context == null ? context = new Path : undefined;
    const {hull, points} = this;
    const h = hull[0] * 2, n = hull.length;
    context.moveTo(points[h], points[h + 1]);
    for (let i = 1; i < n; ++i) {
      const h = 2 * hull[i];
      context.lineTo(points[h], points[h + 1]);
    }
    context.closePath();
    return buffer && buffer.value();
  }
  hullPolygon() {
    const polygon = new Polygon;
    this.renderHull(polygon);
    return polygon.value();
  }
  renderTriangle(i, context) {
    const buffer = context == null ? context = new Path : undefined;
    const {points, triangles} = this;
    const t0 = triangles[i *= 3] * 2;
    const t1 = triangles[i + 1] * 2;
    const t2 = triangles[i + 2] * 2;
    context.moveTo(points[t0], points[t0 + 1]);
    context.lineTo(points[t1], points[t1 + 1]);
    context.lineTo(points[t2], points[t2 + 1]);
    context.closePath();
    return buffer && buffer.value();
  }
  *trianglePolygons() {
    const {triangles} = this;
    for (let i = 0, n = triangles.length / 3; i < n; ++i) {
      yield this.trianglePolygon(i);
    }
  }
  trianglePolygon(i) {
    const polygon = new Polygon;
    this.renderTriangle(i, polygon);
    return polygon.value();
  }
}

Delaunay.from = function(points, fx = pointX, fy = pointY, that) {
  return new Delaunay("length" in points
      ? flatArray(points, fx, fy, that)
      : Float64Array.from(flatIterable(points, fx, fy, that)));
};

function flatArray(points, fx, fy, that) {
  const n = points.length;
  const array = new Float64Array(n * 2);
  for (let i = 0; i < n; ++i) {
    const p = points[i];
    array[i * 2] = fx.call(that, p, i, points);
    array[i * 2 + 1] = fy.call(that, p, i, points);
  }
  return array;
}

function* flatIterable(points, fx, fy, that) {
  let i = 0;
  for (const p of points) {
    yield fx.call(that, p, i, points);
    yield fy.call(that, p, i, points);
    ++i;
  }
}

function Voronoi$1(params) {
  Transform.call(this, null, params);
}

Voronoi$1.Definition = {
  "type": "Voronoi",
  "metadata": {"modifies": true},
  "params": [
    { "name": "x", "type": "field", "required": true },
    { "name": "y", "type": "field", "required": true },
    { "name": "size", "type": "number", "array": true, "length": 2 },
    { "name": "extent", "type": "array", "array": true, "length": 2,
      "default": [[-1e5, -1e5], [1e5, 1e5]],
      "content": {"type": "number", "array": true, "length": 2} },
    { "name": "as", "type": "string", "default": "path" }
  ]
};

const prototype$1o = inherits(Voronoi$1, Transform);

const defaultExtent = [-1e5, -1e5, 1e5, 1e5];

prototype$1o.transform = function(_, pulse) {
  const as = _.as || 'path',
        data = pulse.source;

  // nothing to do if no data
  if (!data || !data.length) return pulse;

  // configure and construct voronoi diagram
  let s = _.size;
  s = s ? [0, 0, s[0], s[1]]
    : (s = _.extent) ? [s[0][0], s[0][1], s[1][0], s[1][1]]
    : defaultExtent;

  const voronoi = this.value = Delaunay.from(data, _.x, _.y).voronoi(s);

  // map polygons to paths
  for (let i=0, n=data.length; i<n; ++i) {
    const polygon = voronoi.cellPolygon(i);
    data[i][as] = polygon ? toPathString(polygon) : null;
  }

  return pulse.reflow(_.modified()).modifies(as);
};

// suppress duplicated end point vertices
function toPathString(p) {
  const x = p[0][0],
        y = p[0][1];

  let n = p.length - 1;
  for (; p[n][0] === x && p[n][1] === y; --n);

  return 'M' + p.slice(0, n + 1).join('L') + 'Z';
}



var voronoi = /*#__PURE__*/Object.freeze({
  __proto__: null,
  voronoi: Voronoi$1
});

/*
Copyright (c) 2013, Jason Davies.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

  * Redistributions of source code must retain the above copyright notice, this
    list of conditions and the following disclaimer.

  * Redistributions in binary form must reproduce the above copyright notice,
    this list of conditions and the following disclaimer in the documentation
    and/or other materials provided with the distribution.

  * The name Jason Davies may not be used to endorse or promote products
    derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL JASON DAVIES BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

// Word cloud layout by Jason Davies, https://www.jasondavies.com/wordcloud/
// Algorithm due to Jonathan Feinberg, http://static.mrfeinberg.com/bv_ch03.pdf

var cloudRadians = Math.PI / 180,
    cw = 1 << 11 >> 5,
    ch = 1 << 11;

function cloud() {
  var size = [256, 256],
      text,
      font,
      fontSize,
      fontStyle,
      fontWeight,
      rotate,
      padding,
      spiral = archimedeanSpiral,
      words = [],
      random = Math.random,
      cloud = {};

  cloud.layout = function() {
    var contextAndRatio = getContext(domCanvas()),
        board = zeroArray((size[0] >> 5) * size[1]),
        bounds = null,
        n = words.length,
        i = -1,
        tags = [],
        data = words.map(function(d) {
          return {
            text: text(d),
            font: font(d),
            style: fontStyle(d),
            weight: fontWeight(d),
            rotate: rotate(d),
            size: ~~(fontSize(d) + 1e-14),
            padding: padding(d),
            xoff: 0,
            yoff: 0,
            x1: 0,
            y1: 0,
            x0: 0,
            y0: 0,
            hasText: false,
            sprite: null,
            datum: d
          };
        }).sort(function(a, b) { return b.size - a.size; });

    while (++i < n) {
      var d = data[i];
      d.x = (size[0] * (random() + .5)) >> 1;
      d.y = (size[1] * (random() + .5)) >> 1;
      cloudSprite(contextAndRatio, d, data, i);
      if (d.hasText && place(board, d, bounds)) {
        tags.push(d);
        if (bounds) cloudBounds(bounds, d);
        else bounds = [{x: d.x + d.x0, y: d.y + d.y0}, {x: d.x + d.x1, y: d.y + d.y1}];
        // Temporary hack
        d.x -= size[0] >> 1;
        d.y -= size[1] >> 1;
      }
    }

    return tags;
  };

  function getContext(canvas) {
    canvas.width = canvas.height = 1;
    var ratio = Math.sqrt(canvas.getContext("2d").getImageData(0, 0, 1, 1).data.length >> 2);
    canvas.width = (cw << 5) / ratio;
    canvas.height = ch / ratio;

    var context = canvas.getContext("2d");
    context.fillStyle = context.strokeStyle = "red";
    context.textAlign = "center";

    return {context: context, ratio: ratio};
  }

  function place(board, tag, bounds) {
    var startX = tag.x,
        startY = tag.y,
        maxDelta = Math.sqrt(size[0] * size[0] + size[1] * size[1]),
        s = spiral(size),
        dt = random() < .5 ? 1 : -1,
        t = -dt,
        dxdy,
        dx,
        dy;

    while (dxdy = s(t += dt)) {
      dx = ~~dxdy[0];
      dy = ~~dxdy[1];

      if (Math.min(Math.abs(dx), Math.abs(dy)) >= maxDelta) break;

      tag.x = startX + dx;
      tag.y = startY + dy;

      if (tag.x + tag.x0 < 0 || tag.y + tag.y0 < 0 ||
          tag.x + tag.x1 > size[0] || tag.y + tag.y1 > size[1]) continue;
      // TODO only check for collisions within current bounds.
      if (!bounds || !cloudCollide(tag, board, size[0])) {
        if (!bounds || collideRects(tag, bounds)) {
          var sprite = tag.sprite,
              w = tag.width >> 5,
              sw = size[0] >> 5,
              lx = tag.x - (w << 4),
              sx = lx & 0x7f,
              msx = 32 - sx,
              h = tag.y1 - tag.y0,
              x = (tag.y + tag.y0) * sw + (lx >> 5),
              last;
          for (var j = 0; j < h; j++) {
            last = 0;
            for (var i = 0; i <= w; i++) {
              board[x + i] |= (last << msx) | (i < w ? (last = sprite[j * w + i]) >>> sx : 0);
            }
            x += sw;
          }
          tag.sprite = null;
          return true;
        }
      }
    }
    return false;
  }

  cloud.words = function(_) {
    if (arguments.length) {
      words = _;
      return cloud;
    } else {
      return words;
    }
  };

  cloud.size = function(_) {
    if (arguments.length) {
      size = [+_[0], +_[1]];
      return cloud;
    } else {
      return size;
    }
  };

  cloud.font = function(_) {
    if (arguments.length) {
      font = functor(_);
      return cloud;
    } else {
      return font;
    }
  };

  cloud.fontStyle = function(_) {
    if (arguments.length) {
      fontStyle = functor(_);
      return cloud;
    } else {
      return fontStyle;
    }
  };

  cloud.fontWeight = function(_) {
    if (arguments.length) {
      fontWeight = functor(_);
      return cloud;
    } else {
      return fontWeight;
    }
  };

  cloud.rotate = function(_) {
    if (arguments.length) {
      rotate = functor(_);
      return cloud;
    } else {
      return rotate;
    }
  };

  cloud.text = function(_) {
    if (arguments.length) {
      text = functor(_);
      return cloud;
    } else {
      return text;
    }
  };

  cloud.spiral = function(_) {
    if (arguments.length) {
      spiral = spirals[_] || _;
      return cloud;
    } else {
      return spiral;
    }
  };

  cloud.fontSize = function(_) {
    if (arguments.length) {
      fontSize = functor(_);
      return cloud;
    } else {
      return fontSize;
    }
  };

  cloud.padding = function(_) {
    if (arguments.length) {
      padding = functor(_);
      return cloud;
    } else {
      return padding;
    }
  };

  cloud.random = function(_) {
    if (arguments.length) {
      random = _;
      return cloud;
    } else {
      return random;
    }
  };

  return cloud;
}

// Fetches a monochrome sprite bitmap for the specified text.
// Load in batches for speed.
function cloudSprite(contextAndRatio, d, data, di) {
  if (d.sprite) return;
  var c = contextAndRatio.context,
      ratio = contextAndRatio.ratio;

  c.clearRect(0, 0, (cw << 5) / ratio, ch / ratio);
  var x = 0,
      y = 0,
      maxh = 0,
      n = data.length,
      w, w32, h, i, j;
  --di;
  while (++di < n) {
    d = data[di];
    c.save();
    c.font = d.style + " " + d.weight + " " + ~~((d.size + 1) / ratio) + "px " + d.font;
    w = c.measureText(d.text + "m").width * ratio;
    h = d.size << 1;
    if (d.rotate) {
      var sr = Math.sin(d.rotate * cloudRadians),
          cr = Math.cos(d.rotate * cloudRadians),
          wcr = w * cr,
          wsr = w * sr,
          hcr = h * cr,
          hsr = h * sr;
      w = (Math.max(Math.abs(wcr + hsr), Math.abs(wcr - hsr)) + 0x1f) >> 5 << 5;
      h = ~~Math.max(Math.abs(wsr + hcr), Math.abs(wsr - hcr));
    } else {
      w = (w + 0x1f) >> 5 << 5;
    }
    if (h > maxh) maxh = h;
    if (x + w >= (cw << 5)) {
      x = 0;
      y += maxh;
      maxh = 0;
    }
    if (y + h >= ch) break;
    c.translate((x + (w >> 1)) / ratio, (y + (h >> 1)) / ratio);
    if (d.rotate) c.rotate(d.rotate * cloudRadians);
    c.fillText(d.text, 0, 0);
    if (d.padding) {
      c.lineWidth = 2 * d.padding;
      c.strokeText(d.text, 0, 0);
    }
    c.restore();
    d.width = w;
    d.height = h;
    d.xoff = x;
    d.yoff = y;
    d.x1 = w >> 1;
    d.y1 = h >> 1;
    d.x0 = -d.x1;
    d.y0 = -d.y1;
    d.hasText = true;
    x += w;
  }
  var pixels = c.getImageData(0, 0, (cw << 5) / ratio, ch / ratio).data,
      sprite = [];
  while (--di >= 0) {
    d = data[di];
    if (!d.hasText) continue;
    w = d.width;
    w32 = w >> 5;
    h = d.y1 - d.y0;
    // Zero the buffer
    for (i = 0; i < h * w32; i++) sprite[i] = 0;
    x = d.xoff;
    if (x == null) return;
    y = d.yoff;
    var seen = 0,
        seenRow = -1;
    for (j = 0; j < h; j++) {
      for (i = 0; i < w; i++) {
        var k = w32 * j + (i >> 5),
            m = pixels[((y + j) * (cw << 5) + (x + i)) << 2] ? 1 << (31 - (i % 32)) : 0;
        sprite[k] |= m;
        seen |= m;
      }
      if (seen) seenRow = j;
      else {
        d.y0++;
        h--;
        j--;
        y++;
      }
    }
    d.y1 = d.y0 + seenRow;
    d.sprite = sprite.slice(0, (d.y1 - d.y0) * w32);
  }
}

// Use mask-based collision detection.
function cloudCollide(tag, board, sw) {
  sw >>= 5;
  var sprite = tag.sprite,
      w = tag.width >> 5,
      lx = tag.x - (w << 4),
      sx = lx & 0x7f,
      msx = 32 - sx,
      h = tag.y1 - tag.y0,
      x = (tag.y + tag.y0) * sw + (lx >> 5),
      last;
  for (var j = 0; j < h; j++) {
    last = 0;
    for (var i = 0; i <= w; i++) {
      if (((last << msx) | (i < w ? (last = sprite[j * w + i]) >>> sx : 0))
          & board[x + i]) return true;
    }
    x += sw;
  }
  return false;
}

function cloudBounds(bounds, d) {
  var b0 = bounds[0],
      b1 = bounds[1];
  if (d.x + d.x0 < b0.x) b0.x = d.x + d.x0;
  if (d.y + d.y0 < b0.y) b0.y = d.y + d.y0;
  if (d.x + d.x1 > b1.x) b1.x = d.x + d.x1;
  if (d.y + d.y1 > b1.y) b1.y = d.y + d.y1;
}

function collideRects(a, b) {
  return a.x + a.x1 > b[0].x && a.x + a.x0 < b[1].x && a.y + a.y1 > b[0].y && a.y + a.y0 < b[1].y;
}

function archimedeanSpiral(size) {
  var e = size[0] / size[1];
  return function(t) {
    return [e * (t *= .1) * Math.cos(t), t * Math.sin(t)];
  };
}

function rectangularSpiral(size) {
  var dy = 4,
      dx = dy * size[0] / size[1],
      x = 0,
      y = 0;
  return function(t) {
    var sign = t < 0 ? -1 : 1;
    // See triangular numbers: T_n = n * (n + 1) / 2.
    switch ((Math.sqrt(1 + 4 * sign * t) - sign) & 3) {
      case 0:  x += dx; break;
      case 1:  y += dy; break;
      case 2:  x -= dx; break;
      default: y -= dy; break;
    }
    return [x, y];
  };
}

// TODO reuse arrays?
function zeroArray(n) {
  var a = [],
      i = -1;
  while (++i < n) a[i] = 0;
  return a;
}

function functor(d) {
  return typeof d === "function" ? d : function() { return d; };
}

var spirals = {
  archimedean: archimedeanSpiral,
  rectangular: rectangularSpiral
};

var Output$5 = ['x', 'y', 'font', 'fontSize', 'fontStyle', 'fontWeight', 'angle'];

var Params$1 = ['text', 'font', 'rotate', 'fontSize', 'fontStyle', 'fontWeight'];

function Wordcloud(params) {
  Transform.call(this, cloud(), params);
}

Wordcloud.Definition = {
  "type": "Wordcloud",
  "metadata": {"modifies": true},
  "params": [
    { "name": "size", "type": "number", "array": true, "length": 2 },
    { "name": "font", "type": "string", "expr": true, "default": "sans-serif" },
    { "name": "fontStyle", "type": "string", "expr": true, "default": "normal" },
    { "name": "fontWeight", "type": "string", "expr": true, "default": "normal" },
    { "name": "fontSize", "type": "number", "expr": true, "default": 14 },
    { "name": "fontSizeRange", "type": "number", "array": "nullable", "default": [10, 50] },
    { "name": "rotate", "type": "number", "expr": true, "default": 0 },
    { "name": "text", "type": "field" },
    { "name": "spiral", "type": "string", "values": ["archimedean", "rectangular"] },
    { "name": "padding", "type": "number", "expr": true },
    { "name": "as", "type": "string", "array": true, "length": 7, "default": Output$5 }
  ]
};

var prototype$1p = inherits(Wordcloud, Transform);

prototype$1p.transform = function(_, pulse) {
  if (_.size && !(_.size[0] && _.size[1])) {
    error('Wordcloud size dimensions must be non-zero.');
  }

  function modp(param) {
    var p = _[param];
    return isFunction(p) && pulse.modified(p.fields);
  }

  var mod = _.modified();
  if (!(mod || pulse.changed(pulse.ADD_REM) || Params$1.some(modp))) return;

  var data = pulse.materialize(pulse.SOURCE).source,
      layout = this.value,
      as = _.as || Output$5,
      fontSize = _.fontSize || 14,
      range;

  isFunction(fontSize)
    ? (range = _.fontSizeRange)
    : (fontSize = constant(fontSize));

  // create font size scaling function as needed
  if (range) {
    var fsize = fontSize,
        sizeScale = scale$2('sqrt')()
          .domain(extent(data, fsize))
          .range(range);
    fontSize = function(x) { return sizeScale(fsize(x)); };
  }

  data.forEach(function(t) {
    t[as[0]] = NaN;
    t[as[1]] = NaN;
    t[as[3]] = 0;
  });

  // configure layout
  var words = layout
    .words(data)
    .text(_.text)
    .size(_.size || [500, 500])
    .padding(_.padding || 1)
    .spiral(_.spiral || 'archimedean')
    .rotate(_.rotate || 0)
    .font(_.font || 'sans-serif')
    .fontStyle(_.fontStyle || 'normal')
    .fontWeight(_.fontWeight || 'normal')
    .fontSize(fontSize)
    .random(random)
    .layout();

  var size = layout.size(),
      dx = size[0] >> 1,
      dy = size[1] >> 1,
      i = 0,
      n = words.length,
      w, t;

  for (; i<n; ++i) {
    w = words[i];
    t = w.datum;
    t[as[0]] = w.x + dx;
    t[as[1]] = w.y + dy;
    t[as[2]] = w.font;
    t[as[3]] = w.size;
    t[as[4]] = w.style;
    t[as[5]] = w.weight;
    t[as[6]] = w.rotate;
  }

  return pulse.reflow(mod).modifies(as);
};



var wordcloud = /*#__PURE__*/Object.freeze({
  __proto__: null,
  wordcloud: Wordcloud
});

function array8(n) { return new Uint8Array(n); }

function array16(n) { return new Uint16Array(n); }

function array32(n) { return new Uint32Array(n); }

/**
 * Maintains CrossFilter state.
 */
function Bitmaps() {

  var width = 8,
      data = [],
      seen = array32(0),
      curr = array$1(0, width),
      prev = array$1(0, width);

  return {

    data: function() { return data; },

    seen: function() {
      return (seen = lengthen(seen, data.length));
    },

    add: function(array) {
      for (var i=0, j=data.length, n=array.length, t; i<n; ++i) {
        t = array[i];
        t._index = j++;
        data.push(t);
      }
    },

    remove: function(num, map) { // map: index -> boolean (true => remove)
      var n = data.length,
          copy = Array(n - num),
          reindex = data, // reuse old data array for index map
          t, i, j;

      // seek forward to first removal
      for (i=0; !map[i] && i<n; ++i) {
        copy[i] = data[i];
        reindex[i] = i;
      }

      // condense arrays
      for (j=i; i<n; ++i) {
        t = data[i];
        if (!map[i]) {
          reindex[i] = j;
          curr[j] = curr[i];
          prev[j] = prev[i];
          copy[j] = t;
          t._index = j++;
        } else {
          reindex[i] = -1;
        }
        curr[i] = 0; // clear unused bits
      }

      data = copy;
      return reindex;
    },

    size: function() { return data.length; },

    curr: function() { return curr; },

    prev: function() { return prev; },

    reset: function(k) { prev[k] = curr[k]; },

    all: function() {
      return width < 0x101 ? 0xff : width < 0x10001 ? 0xffff : 0xffffffff;
    },

    set: function(k, one) { curr[k] |= one; },

    clear: function(k, one) { curr[k] &= ~one; },

    resize: function(n, m) {
      var k = curr.length;
      if (n > k || m > width) {
        width = Math.max(m, width);
        curr = array$1(n, width, curr);
        prev = array$1(n, width);
      }
    }
  };
}

function lengthen(array, length, copy) {
  if (array.length >= length) return array;
  copy = copy || new array.constructor(length);
  copy.set(array);
  return copy;
}

function array$1(n, m, array) {
  var copy = (m < 0x101 ? array8 : m < 0x10001 ? array16 : array32)(n);
  if (array) copy.set(array);
  return copy;
}

function Dimension(index, i, query) {
  var bit = (1 << i);

  return {
    one:     bit,
    zero:    ~bit,
    range:   query.slice(),
    bisect:  index.bisect,
    index:   index.index,
    size:    index.size,

    onAdd: function(added, curr) {
      var dim = this,
          range = dim.bisect(dim.range, added.value),
          idx = added.index,
          lo = range[0],
          hi = range[1],
          n1 = idx.length, i;

      for (i=0;  i<lo; ++i) curr[idx[i]] |= bit;
      for (i=hi; i<n1; ++i) curr[idx[i]] |= bit;
      return dim;
    }
  };
}

/**
 * Maintains a list of values, sorted by key.
 */
function SortedIndex() {
  var index = array32(0),
      value = [],
      size = 0;

  function insert(key, data, base) {
    if (!data.length) return [];

    var n0 = size,
        n1 = data.length,
        addv = Array(n1),
        addi = array32(n1),
        oldv, oldi, i;

    for (i=0; i<n1; ++i) {
      addv[i] = key(data[i]);
      addi[i] = i;
    }
    addv = sort(addv, addi);

    if (n0) {
      oldv = value;
      oldi = index;
      value = Array(n0 + n1);
      index = array32(n0 + n1);
      merge$1(base, oldv, oldi, n0, addv, addi, n1, value, index);
    } else {
      if (base > 0) for (i=0; i<n1; ++i) {
        addi[i] += base;
      }
      value = addv;
      index = addi;
    }
    size = n0 + n1;

    return {index: addi, value: addv};
  }

  function remove(num, map) {
    // map: index -> remove
    var n = size,
        idx, i, j;

    // seek forward to first removal
    for (i=0; !map[index[i]] && i<n; ++i);

    // condense index and value arrays
    for (j=i; i<n; ++i) {
      if (!map[idx=index[i]]) {
        index[j] = idx;
        value[j] = value[i];
        ++j;
      }
    }

    size = n - num;
  }

  function reindex(map) {
    for (var i=0, n=size; i<n; ++i) {
      index[i] = map[index[i]];
    }
  }

  function bisect(range, array) {
    var n;
    if (array) {
      n = array.length;
    } else {
      array = value;
      n = size;
    }
    return [
      bisectLeft(array, range[0], 0, n),
      bisectRight(array, range[1], 0, n)
    ];
  }

  return {
    insert:  insert,
    remove:  remove,
    bisect:  bisect,
    reindex: reindex,
    index:   function() { return index; },
    size:    function() { return size; }
  };
}

function sort(values, index) {
  values.sort.call(index, function(a, b) {
    var x = values[a],
        y = values[b];
    return x < y ? -1 : x > y ? 1 : 0;
  });
  return permute(values, index);
}

function merge$1(base, value0, index0, n0, value1, index1, n1, value, index) {
  var i0 = 0, i1 = 0, i;

  for (i=0; i0 < n0 && i1 < n1; ++i) {
    if (value0[i0] < value1[i1]) {
      value[i] = value0[i0];
      index[i] = index0[i0++];
    } else {
      value[i] = value1[i1];
      index[i] = index1[i1++] + base;
    }
  }

  for (; i0 < n0; ++i0, ++i) {
    value[i] = value0[i0];
    index[i] = index0[i0];
  }

  for (; i1 < n1; ++i1, ++i) {
    value[i] = value1[i1];
    index[i] = index1[i1] + base;
  }
}

/**
 * An indexed multi-dimensional filter.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {Array<function(object): *>} params.fields - An array of dimension accessors to filter.
 * @param {Array} params.query - An array of per-dimension range queries.
 */
function CrossFilter(params) {
  Transform.call(this, Bitmaps(), params);
  this._indices = null;
  this._dims = null;
}

CrossFilter.Definition = {
  "type": "CrossFilter",
  "metadata": {},
  "params": [
    { "name": "fields", "type": "field", "array": true, "required": true },
    { "name": "query", "type": "array", "array": true, "required": true,
      "content": {"type": "number", "array": true, "length": 2} }
  ]
};

var prototype$1q = inherits(CrossFilter, Transform);

prototype$1q.transform = function(_, pulse) {
  if (!this._dims) {
    return this.init(_, pulse);
  } else {
    var init = _.modified('fields')
          || _.fields.some(function(f) { return pulse.modified(f.fields); });

    return init
      ? this.reinit(_, pulse)
      : this.eval(_, pulse);
  }
};

prototype$1q.init = function(_, pulse) {
  var fields = _.fields,
      query = _.query,
      indices = this._indices = {},
      dims = this._dims = [],
      m = query.length,
      i = 0, key, index;

  // instantiate indices and dimensions
  for (; i<m; ++i) {
    key = fields[i].fname;
    index = indices[key] || (indices[key] = SortedIndex());
    dims.push(Dimension(index, i, query[i]));
  }

  return this.eval(_, pulse);
};

prototype$1q.reinit = function(_, pulse) {
  var output = pulse.materialize().fork(),
      fields = _.fields,
      query = _.query,
      indices = this._indices,
      dims = this._dims,
      bits = this.value,
      curr = bits.curr(),
      prev = bits.prev(),
      all = bits.all(),
      out = (output.rem = output.add),
      mod = output.mod,
      m = query.length,
      adds = {}, add, index, key,
      mods, remMap, modMap, i, n, f;

  // set prev to current state
  prev.set(curr);

  // if pulse has remove tuples, process them first
  if (pulse.rem.length) {
    remMap = this.remove(_, pulse, output);
  }

  // if pulse has added tuples, add them to state
  if (pulse.add.length) {
    bits.add(pulse.add);
  }

  // if pulse has modified tuples, create an index map
  if (pulse.mod.length) {
    modMap = {};
    for (mods=pulse.mod, i=0, n=mods.length; i<n; ++i) {
      modMap[mods[i]._index] = 1;
    }
  }

  // re-initialize indices as needed, update curr bitmap
  for (i=0; i<m; ++i) {
    f = fields[i];
    if (!dims[i] || _.modified('fields', i) || pulse.modified(f.fields)) {
      key = f.fname;
      if (!(add = adds[key])) {
        indices[key] = index = SortedIndex();
        adds[key] = add = index.insert(f, pulse.source, 0);
      }
      dims[i] = Dimension(index, i, query[i]).onAdd(add, curr);
    }
  }

  // visit each tuple
  // if filter state changed, push index to add/rem
  // else if in mod and passes a filter, push index to mod
  for (i=0, n=bits.data().length; i<n; ++i) {
    if (remMap[i]) { // skip if removed tuple
      continue;
    } else if (prev[i] !== curr[i]) { // add if state changed
      out.push(i);
    } else if (modMap[i] && curr[i] !== all) { // otherwise, pass mods through
      mod.push(i);
    }
  }

  bits.mask = (1 << m) - 1;
  return output;
};

prototype$1q.eval = function(_, pulse) {
  var output = pulse.materialize().fork(),
      m = this._dims.length,
      mask = 0;

  if (pulse.rem.length) {
    this.remove(_, pulse, output);
    mask |= (1 << m) - 1;
  }

  if (_.modified('query') && !_.modified('fields')) {
    mask |= this.update(_, pulse, output);
  }

  if (pulse.add.length) {
    this.insert(_, pulse, output);
    mask |= (1 << m) - 1;
  }

  if (pulse.mod.length) {
    this.modify(pulse, output);
    mask |= (1 << m) - 1;
  }

  this.value.mask = mask;
  return output;
};

prototype$1q.insert = function(_, pulse, output) {
  var tuples = pulse.add,
      bits = this.value,
      dims = this._dims,
      indices = this._indices,
      fields = _.fields,
      adds = {},
      out = output.add,
      k = bits.size(),
      n = k + tuples.length,
      m = dims.length, j, key, add;

  // resize bitmaps and add tuples as needed
  bits.resize(n, m);
  bits.add(tuples);

  var curr = bits.curr(),
      prev = bits.prev(),
      all  = bits.all();

  // add to dimensional indices
  for (j=0; j<m; ++j) {
    key = fields[j].fname;
    add = adds[key] || (adds[key] = indices[key].insert(fields[j], tuples, k));
    dims[j].onAdd(add, curr);
  }

  // set previous filters, output if passes at least one filter
  for (; k<n; ++k) {
    prev[k] = all;
    if (curr[k] !== all) out.push(k);
  }
};

prototype$1q.modify = function(pulse, output) {
  var out = output.mod,
      bits = this.value,
      curr = bits.curr(),
      all  = bits.all(),
      tuples = pulse.mod,
      i, n, k;

  for (i=0, n=tuples.length; i<n; ++i) {
    k = tuples[i]._index;
    if (curr[k] !== all) out.push(k);
  }
};

prototype$1q.remove = function(_, pulse, output) {
  var indices = this._indices,
      bits = this.value,
      curr = bits.curr(),
      prev = bits.prev(),
      all  = bits.all(),
      map = {},
      out = output.rem,
      tuples = pulse.rem,
      i, n, k, f;

  // process tuples, output if passes at least one filter
  for (i=0, n=tuples.length; i<n; ++i) {
    k = tuples[i]._index;
    map[k] = 1; // build index map
    prev[k] = (f = curr[k]);
    curr[k] = all;
    if (f !== all) out.push(k);
  }

  // remove from dimensional indices
  for (k in indices) {
    indices[k].remove(n, map);
  }

  this.reindex(pulse, n, map);
  return map;
};

// reindex filters and indices after propagation completes
prototype$1q.reindex = function(pulse, num, map) {
  var indices = this._indices,
      bits = this.value;

  pulse.runAfter(function() {
    var indexMap = bits.remove(num, map);
    for (var key in indices) indices[key].reindex(indexMap);
  });
};

prototype$1q.update = function(_, pulse, output) {
  var dims = this._dims,
      query = _.query,
      stamp = pulse.stamp,
      m = dims.length,
      mask = 0, i, q;

  // survey how many queries have changed
  output.filters = 0;
  for (q=0; q<m; ++q) {
    if (_.modified('query', q)) { i = q; ++mask; }
  }

  if (mask === 1) {
    // only one query changed, use more efficient update
    mask = dims[i].one;
    this.incrementOne(dims[i], query[i], output.add, output.rem);
  } else {
    // multiple queries changed, perform full record keeping
    for (q=0, mask=0; q<m; ++q) {
      if (!_.modified('query', q)) continue;
      mask |= dims[q].one;
      this.incrementAll(dims[q], query[q], stamp, output.add);
      output.rem = output.add; // duplicate add/rem for downstream resolve
    }
  }

  return mask;
};

prototype$1q.incrementAll = function(dim, query, stamp, out) {
  var bits = this.value,
      seen = bits.seen(),
      curr = bits.curr(),
      prev = bits.prev(),
      index = dim.index(),
      old = dim.bisect(dim.range),
      range = dim.bisect(query),
      lo1 = range[0],
      hi1 = range[1],
      lo0 = old[0],
      hi0 = old[1],
      one = dim.one,
      i, j, k;

  // Fast incremental update based on previous lo index.
  if (lo1 < lo0) {
    for (i = lo1, j = Math.min(lo0, hi1); i < j; ++i) {
      k = index[i];
      if (seen[k] !== stamp) {
        prev[k] = curr[k];
        seen[k] = stamp;
        out.push(k);
      }
      curr[k] ^= one;
    }
  } else if (lo1 > lo0) {
    for (i = lo0, j = Math.min(lo1, hi0); i < j; ++i) {
      k = index[i];
      if (seen[k] !== stamp) {
        prev[k] = curr[k];
        seen[k] = stamp;
        out.push(k);
      }
      curr[k] ^= one;
    }
  }

  // Fast incremental update based on previous hi index.
  if (hi1 > hi0) {
    for (i = Math.max(lo1, hi0), j = hi1; i < j; ++i) {
      k = index[i];
      if (seen[k] !== stamp) {
        prev[k] = curr[k];
        seen[k] = stamp;
        out.push(k);
      }
      curr[k] ^= one;
    }
  } else if (hi1 < hi0) {
    for (i = Math.max(lo0, hi1), j = hi0; i < j; ++i) {
      k = index[i];
      if (seen[k] !== stamp) {
        prev[k] = curr[k];
        seen[k] = stamp;
        out.push(k);
      }
      curr[k] ^= one;
    }
  }

  dim.range = query.slice();
};

prototype$1q.incrementOne = function(dim, query, add, rem) {
  var bits = this.value,
      curr = bits.curr(),
      index = dim.index(),
      old = dim.bisect(dim.range),
      range = dim.bisect(query),
      lo1 = range[0],
      hi1 = range[1],
      lo0 = old[0],
      hi0 = old[1],
      one = dim.one,
      i, j, k;

  // Fast incremental update based on previous lo index.
  if (lo1 < lo0) {
    for (i = lo1, j = Math.min(lo0, hi1); i < j; ++i) {
      k = index[i];
      curr[k] ^= one;
      add.push(k);
    }
  } else if (lo1 > lo0) {
    for (i = lo0, j = Math.min(lo1, hi0); i < j; ++i) {
      k = index[i];
      curr[k] ^= one;
      rem.push(k);
    }
  }

  // Fast incremental update based on previous hi index.
  if (hi1 > hi0) {
    for (i = Math.max(lo1, hi0), j = hi1; i < j; ++i) {
      k = index[i];
      curr[k] ^= one;
      add.push(k);
    }
  } else if (hi1 < hi0) {
    for (i = Math.max(lo0, hi1), j = hi0; i < j; ++i) {
      k = index[i];
      curr[k] ^= one;
      rem.push(k);
    }
  }

  dim.range = query.slice();
};

/**
 * Selectively filters tuples by resolving against a filter bitmap.
 * Useful for processing the output of a cross-filter transform.
 * @constructor
 * @param {object} params - The parameters for this operator.
 * @param {object} params.ignore - A bit mask indicating which filters to ignore.
 * @param {object} params.filter - The per-tuple filter bitmaps. Typically this
 *   parameter value is a reference to a {@link CrossFilter} transform.
 */
function ResolveFilter(params) {
  Transform.call(this, null, params);
}

ResolveFilter.Definition = {
  "type": "ResolveFilter",
  "metadata": {},
  "params": [
    { "name": "ignore", "type": "number", "required": true,
      "description": "A bit mask indicating which filters to ignore." },
    { "name": "filter", "type": "object", "required": true,
      "description": "Per-tuple filter bitmaps from a CrossFilter transform." }
  ]
};

var prototype$1r = inherits(ResolveFilter, Transform);

prototype$1r.transform = function(_, pulse) {
  var ignore = ~(_.ignore || 0), // bit mask where zeros -> dims to ignore
      bitmap = _.filter,
      mask = bitmap.mask;

  // exit early if no relevant filter changes
  if ((mask & ignore) === 0) return pulse.StopPropagation;

  var output = pulse.fork(pulse.ALL),
      data = bitmap.data(),
      curr = bitmap.curr(),
      prev = bitmap.prev(),
      pass = function(k) {
        return !(curr[k] & ignore) ? data[k] : null;
      };

  // propagate all mod tuples that pass the filter
  output.filter(output.MOD, pass);

  // determine add & rem tuples via filter functions
  // for efficiency, we do *not* populate new arrays,
  // instead we add filter functions applied downstream

  if (!(mask & (mask-1))) { // only one filter changed
    output.filter(output.ADD, pass);
    output.filter(output.REM, function(k) {
      return (curr[k] & ignore) === mask ? data[k] : null;
    });

  } else { // multiple filters changed
    output.filter(output.ADD, function(k) {
      var c = curr[k] & ignore,
          f = !c && (c ^ (prev[k] & ignore));
      return f ? data[k] : null;
    });
    output.filter(output.REM, function(k) {
      var c = curr[k] & ignore,
          f = c && !(c ^ (c ^ (prev[k] & ignore)));
      return f ? data[k] : null;
    });
  }

  // add filter to source data in case of reflow...
  return output.filter(output.SOURCE, function(t) { return pass(t._index); });
};



var xf = /*#__PURE__*/Object.freeze({
  __proto__: null,
  crossfilter: CrossFilter,
  resolvefilter: ResolveFilter
});

var version = "5.9.1";

var Default = 'default';

function cursor(view) {
  var cursor = view._signals.cursor;

  // add cursor signal to dataflow, if needed
  if (!cursor) {
    view._signals.cursor = (cursor = view.add({user: Default, item: null}));
  }

  // evaluate cursor on each mousemove event
  view.on(view.events('view', 'mousemove'), cursor,
    function(_, event) {
      var value = cursor.value,
          user = value ? (isString(value) ? value : value.user) : Default,
          item = event.item && event.item.cursor || null;

      return (value && user === value.user && item == value.item) ? value
        : {user: user, item: item};
    }
  );

  // when cursor signal updates, set visible cursor
  view.add(null, function(_) {
    var user = _.cursor,
        item = this.value;

    if (!isString(user)) {
      item = user.item;
      user = user.user;
    }

    setCursor(user && user !== Default ? user : (item || user));

    return item;
  }, {cursor: cursor});
}

function setCursor(cursor) {
  // set cursor on document body
  // this ensures cursor applies even if dragging out of view
  if (typeof document !== 'undefined' && document.body) {
    document.body.style.cursor = cursor;
  }
}

function dataref(view, name) {
  var data = view._runtime.data;
  if (!hasOwnProperty(data, name)) {
    error('Unrecognized data set: ' + name);
  }
  return data[name];
}

function data(name, values) {
  return arguments.length < 2
    ? dataref(this, name).values.value
    : change.call(this, name, changeset().remove(truthy).insert(values));
}

function change(name, changes) {
  if (!isChangeSet(changes)) {
    error('Second argument to changes must be a changeset.');
  }
  var dataset = dataref(this, name);
  dataset.modified = true;
  return this.pulse(dataset.input, changes);
}

function insert(name, _) {
  return change.call(this, name, changeset().insert(_));
}

function remove(name, _) {
  return change.call(this, name, changeset().remove(_));
}

function width(view) {
  var padding = view.padding();
  return Math.max(0, view._viewWidth + padding.left + padding.right);
}

function height(view) {
  var padding = view.padding();
  return Math.max(0, view._viewHeight + padding.top + padding.bottom);
}

function offset$3(view) {
  var padding = view.padding(),
      origin = view._origin;
  return [
    padding.left + origin[0],
    padding.top + origin[1]
  ];
}

function resizeRenderer(view) {
  var origin = offset$3(view),
      w = width(view),
      h = height(view);

  view._renderer.background(view._background);
  view._renderer.resize(w, h, origin);
  view._handler.origin(origin);

  view._resizeListeners.forEach(function(handler) {
    try {
      handler(w, h);
    } catch (error) {
      view.error(error);
    }
  });
}

/**
 * Extend an event with additional view-specific methods.
 * Adds a new property ('vega') to an event that provides a number
 * of methods for querying information about the current interaction.
 * The vega object provides the following methods:
 *   view - Returns the backing View instance.
 *   item - Returns the currently active scenegraph item (if any).
 *   group - Returns the currently active scenegraph group (if any).
 *     This method accepts a single string-typed argument indicating the name
 *     of the desired parent group. The scenegraph will be traversed from
 *     the item up towards the root to search for a matching group. If no
 *     argument is provided the enclosing group for the active item is
 *     returned, unless the item it itself a group, in which case it is
 *     returned directly.
 *   xy - Returns a two-element array containing the x and y coordinates for
 *     mouse or touch events. For touch events, this is based on the first
 *     elements in the changedTouches array. This method accepts a single
 *     argument: either an item instance or mark name that should serve as
 *     the reference coordinate system. If no argument is provided the
 *     top-level view coordinate system is assumed.
 *   x - Returns the current x-coordinate, accepts the same arguments as xy.
 *   y - Returns the current y-coordinate, accepts the same arguments as xy.
 * @param {Event} event - The input event to extend.
 * @param {Item} item - The currently active scenegraph item (if any).
 * @return {Event} - The extended input event.
 */
function eventExtend(view, event, item) {
  var r  = view._renderer,
      el = r && r.canvas(),
      p, e, translate;

  if (el) {
    translate = offset$3(view);
    e = event.changedTouches ? event.changedTouches[0] : event;
    p = point(e, el);
    p[0] -= translate[0];
    p[1] -= translate[1];
  }

  event.dataflow = view;
  event.item = item;
  event.vega = extension(view, item, p);
  return event;
}

function extension(view, item, point) {
  var itemGroup = item
    ? item.mark.marktype === 'group' ? item : item.mark.group
    : null;

  function group(name) {
    var g = itemGroup, i;
    if (name) for (i = item; i; i = i.mark.group) {
      if (i.mark.name === name) { g = i; break; }
    }
    return g && g.mark && g.mark.interactive ? g : {};
  }

  function xy(item) {
    if (!item) return point;
    if (isString(item)) item = group(item);

    var p = point.slice();
    while (item) {
      p[0] -= item.x || 0;
      p[1] -= item.y || 0;
      item = item.mark && item.mark.group;
    }
    return p;
  }

  return {
    view:  constant(view),
    item:  constant(item || {}),
    group: group,
    xy:    xy,
    x:     function(item) { return xy(item)[0]; },
    y:     function(item) { return xy(item)[1]; }
  };
}

const VIEW = 'view',
      TIMER = 'timer',
      WINDOW = 'window',
      NO_TRAP = {trap: false};

/**
 * Initialize event handling configuration.
 * @param {object} config - The configuration settings.
 * @return {object}
 */
function initializeEventConfig(config) {
  const events = extend({defaults: {}}, config);

  const unpack = (obj, keys) => {
    keys.forEach(k => {
      if (isArray(obj[k])) obj[k] = toSet(obj[k]);
    });
  };

  unpack(events.defaults, ['prevent', 'allow']);
  unpack(events, ['view', 'window', 'selector']);

  return events;
}

function prevent(view, type) {
  var def = view._eventConfig.defaults,
      prevent = def.prevent,
      allow = def.allow;

  return prevent === false || allow === true ? false
    : prevent === true || allow === false ? true
    : prevent ? prevent[type]
    : allow ? !allow[type]
    : view.preventDefault();
}

function permit(view, key, type) {
  const rule = view._eventConfig && view._eventConfig[key];

  if (rule === false || (isObject(rule) && !rule[type])) {
    view.warn(`Blocked ${key} ${type} event listener.`);
    return false;
  }

  return true;
}

/**
 * Create a new event stream from an event source.
 * @param {object} source - The event source to monitor.
 * @param {string} type - The event type.
 * @param {function(object): boolean} [filter] - Event filter function.
 * @return {EventStream}
 */
function events$1(source, type, filter) {
  var view = this,
      s = new EventStream(filter),
      send = function(e, item) {
        view.runAsync(null, () => {
          if (source === VIEW && prevent(view, type)) {
            e.preventDefault();
          }
          s.receive(eventExtend(view, e, item));
        });
      },
      sources;

  if (source === TIMER) {
    if (permit(view, 'timer', type)) {
      view.timer(send, type);
    }
  }

  else if (source === VIEW) {
    if (permit(view, 'view', type)) {
      // send traps errors, so use {trap: false} option
      view.addEventListener(type, send, NO_TRAP);
    }
  }

  else {
    if (source === WINDOW) {
      if (permit(view, 'window', type) && typeof window !== 'undefined') {
        sources = [window];
      }
    } else if (typeof document !== 'undefined') {
      if (permit(view, 'selector', type)) {
        sources = document.querySelectorAll(source);
      }
    }

    if (!sources) {
      view.warn('Can not resolve event source: ' + source);
    } else {
      for (var i=0, n=sources.length; i<n; ++i) {
        sources[i].addEventListener(type, send);
      }

      view._eventListeners.push({
        type:    type,
        sources: sources,
        handler: send
      });
    }
  }

  return s;
}

function itemFilter(event) {
  return event.item;
}

function markTarget(event) {
  // grab upstream collector feeding the mark operator
  return event.item.mark.source;
}

function invoke(name) {
  return function(_, event) {
    return event.vega.view()
      .changeset()
      .encode(event.item, name);
  };
}

function hover(hoverSet, leaveSet) {
  hoverSet = [hoverSet || 'hover'];
  leaveSet = [leaveSet || 'update', hoverSet[0]];

  // invoke hover set upon mouseover
  this.on(
    this.events('view', 'mouseover', itemFilter),
    markTarget,
    invoke(hoverSet)
  );

  // invoke leave set upon mouseout
  this.on(
    this.events('view', 'mouseout', itemFilter),
    markTarget,
    invoke(leaveSet)
  );

  return this;
}

/**
 * Finalize a View instance that is being removed.
 * Cancel any running timers.
 * Remove all external event listeners.
 * Remove any currently displayed tooltip.
 */
function finalize() {
  var tooltip = this._tooltip,
      timers = this._timers,
      listeners = this._eventListeners,
      n, m, e;

  n = timers.length;
  while (--n >= 0) {
    timers[n].stop();
  }

  n = listeners.length;
  while (--n >= 0) {
    e = listeners[n];
    m = e.sources.length;
    while (--m >= 0) {
      e.sources[m].removeEventListener(e.type, e.handler);
    }
  }

  if (tooltip) {
    tooltip.call(this, this._handler, null, null, null);
  }

  return this;
}

function element$1(tag, attr, text) {
  var el = document.createElement(tag);
  for (var key in attr) el.setAttribute(key, attr[key]);
  if (text != null) el.textContent = text;
  return el;
}

var BindClass = 'vega-bind',
    NameClass = 'vega-bind-name',
    RadioClass = 'vega-bind-radio',
    OptionClass = 'vega-option-';

/**
 * Bind a signal to an external HTML input element. The resulting two-way
 * binding will propagate input changes to signals, and propagate signal
 * changes to the input element state. If this view instance has no parent
 * element, we assume the view is headless and no bindings are created.
 * @param {Element|string} el - The parent DOM element to which the input
 *   element should be appended as a child. If string-valued, this argument
 *   will be treated as a CSS selector. If null or undefined, the parent
 *   element of this view will be used as the element.
 * @param {object} param - The binding parameters which specify the signal
 *   to bind to, the input element type, and type-specific configuration.
 * @return {View} - This view instance.
 */
function bind$1(view, el, binding) {
  if (!el) return;

  var param = binding.param,
      bind = binding.state;

  if (!bind) {
    bind = binding.state = {
      elements: null,
      active: false,
      set: null,
      update: function(value) {
        if (value !== view.signal(param.signal)) {
          view.runAsync(null, function() {
            bind.source = true;
            view.signal(param.signal, value);
          });
        }
      }
    };
    if (param.debounce) {
      bind.update = debounce(param.debounce, bind.update);
    }
  }

  generate(bind, el, param, view.signal(param.signal));

  if (!bind.active) {
    view.on(view._signals[param.signal], null, function() {
      bind.source
        ? (bind.source = false)
        : bind.set(view.signal(param.signal));
    });
    bind.active = true;
  }

  return bind;
}

/**
 * Generate an HTML input form element and bind it to a signal.
 */
function generate(bind, el, param, value) {
  var div = element$1('div', {'class': BindClass});

  div.appendChild(element$1('span',
    {'class': NameClass},
    (param.name || param.signal)
  ));

  el.appendChild(div);

  var input = form;
  switch (param.input) {
    case 'checkbox': input = checkbox; break;
    case 'select':   input = select; break;
    case 'radio':    input = radio; break;
    case 'range':    input = range; break;
  }

  input(bind, div, param, value);
}

/**
 * Generates an arbitrary input form element.
 * The input type is controlled via user-provided parameters.
 */
function form(bind, el, param, value) {
  var node = element$1('input');

  for (var key in param) {
    if (key !== 'signal' && key !== 'element') {
      node.setAttribute(key === 'input' ? 'type' : key, param[key]);
    }
  }
  node.setAttribute('name', param.signal);
  node.value = value;

  el.appendChild(node);

  node.addEventListener('input', function() {
    bind.update(node.value);
  });

  bind.elements = [node];
  bind.set = function(value) { node.value = value; };
}

/**
 * Generates a checkbox input element.
 */
function checkbox(bind, el, param, value) {
  var attr = {type: 'checkbox', name: param.signal};
  if (value) attr.checked = true;
  var node = element$1('input', attr);

  el.appendChild(node);

  node.addEventListener('change', function() {
    bind.update(node.checked);
  });

  bind.elements = [node];
  bind.set = function(value) { node.checked = !!value || null; };
}

/**
 * Generates a selection list input element.
 */
function select(bind, el, param, value) {
  var node = element$1('select', {name: param.signal}),
      label = param.labels || [];

  param.options.forEach(function(option, i) {
    var attr = {value: option};
    if (valuesEqual(option, value)) attr.selected = true;
    node.appendChild(element$1('option', attr, (label[i] || option)+''));
  });

  el.appendChild(node);

  node.addEventListener('change', function() {
    bind.update(param.options[node.selectedIndex]);
  });

  bind.elements = [node];
  bind.set = function(value) {
    for (var i=0, n=param.options.length; i<n; ++i) {
      if (valuesEqual(param.options[i], value)) {
        node.selectedIndex = i; return;
      }
    }
  };
}

/**
 * Generates a radio button group.
 */
function radio(bind, el, param, value) {
  var group = element$1('span', {'class': RadioClass}),
      label = param.labels || [];

  el.appendChild(group);

  bind.elements = param.options.map(function(option, i) {
    var id = OptionClass + param.signal + '-' + option;

    var attr = {
      id:    id,
      type:  'radio',
      name:  param.signal,
      value: option
    };
    if (valuesEqual(option, value)) attr.checked = true;

    var input = element$1('input', attr);

    input.addEventListener('change', function() {
      bind.update(option);
    });

    group.appendChild(input);
    group.appendChild(element$1('label', {'for': id}, (label[i] || option)+''));

    return input;
  });

  bind.set = function(value) {
    var nodes = bind.elements,
        i = 0,
        n = nodes.length;
    for (; i<n; ++i) {
      if (valuesEqual(nodes[i].value, value)) nodes[i].checked = true;
    }
  };
}

/**
 * Generates a slider input element.
 */
function range(bind, el, param, value) {
  value = value !== undefined ? value : ((+param.max) + (+param.min)) / 2;

  var max = param.max != null ? param.max : Math.max(100, +value) || 100,
      min = param.min || Math.min(0, max, +value) || 0,
      step = param.step || tickStep(min, max, 100);

  var node = element$1('input', {
    type:  'range',
    name:  param.signal,
    min:   min,
    max:   max,
    step:  step
  });
  node.value = value;

  var label = element$1('label', {}, +value);

  el.appendChild(node);
  el.appendChild(label);

  function update() {
    label.textContent = node.value;
    bind.update(+node.value);
  }

  // subscribe to both input and change
  node.addEventListener('input', update);
  node.addEventListener('change', update);

  bind.elements = [node];
  bind.set = function(value) {
    node.value = value;
    label.textContent = value;
  };
}

function valuesEqual(a, b) {
  return a === b || (a+'' === b+'');
}

function initializeRenderer(view, r, el, constructor, scaleFactor, opt) {
  r = r || new constructor(view.loader());
  return r
    .initialize(el, width(view), height(view), offset$3(view), scaleFactor, opt)
    .background(view._background);
}

function trap(view, fn) {
  return !fn ? null : function() {
    try {
      fn.apply(this, arguments);
    } catch (error) {
      view.error(error);
    }
  };
}

function initializeHandler(view, prevHandler, el, constructor) {
  // instantiate scenegraph handler
  var handler = new constructor(view.loader(), trap(view, view.tooltip()))
    .scene(view.scenegraph().root)
    .initialize(el, offset$3(view), view);

  // transfer event handlers
  if (prevHandler) {
    prevHandler.handlers().forEach(function(h) {
      handler.on(h.type, h.handler);
    });
  }

  return handler;
}

function initialize$1(el, elBind) {
  var view = this,
      type = view._renderType,
      config = view._eventConfig.bind,
      module = renderModule(type),
      Handler, Renderer;

  // containing dom element
  el = view._el = el ? lookup$4(view, el) : null;

  // select appropriate renderer & handler
  if (!module) view.error('Unrecognized renderer type: ' + type);
  Handler = module.handler || CanvasHandler;
  Renderer = (el ? module.renderer : module.headless);

  // initialize renderer and input handler
  view._renderer = !Renderer ? null
    : initializeRenderer(view, view._renderer, el, Renderer);
  view._handler = initializeHandler(view, view._handler, el, Handler);
  view._redraw = true;

  // initialize signal bindings
  if (el && config !== 'none') {
    elBind = elBind ? (view._elBind = lookup$4(view, elBind))
      : el.appendChild(element$1('div', {'class': 'vega-bindings'}));

    view._bind.forEach(function(_) {
      if (_.param.element && config !== 'container') {
        _.element = lookup$4(view, _.param.element);
      }
    });

    view._bind.forEach(function(_) {
      bind$1(view, _.element || elBind, _);
    });
  }

  return view;
}

function lookup$4(view, el) {
  if (typeof el === 'string') {
    if (typeof document !== 'undefined') {
      el = document.querySelector(el);
      if (!el) {
        view.error('Signal bind element not found: ' + el);
        return null;
      }
    } else {
      view.error('DOM document instance not found.');
      return null;
    }
  }
  if (el) {
    try {
      el.innerHTML = '';
    } catch (e) {
      el = null;
      view.error(e);
    }
  }
  return el;
}

/**
 * Render the current scene in a headless fashion.
 * This method is asynchronous, returning a Promise instance.
 * @return {Promise} - A Promise that resolves to a renderer.
 */
async function renderHeadless(view, type, scaleFactor, opt) {
  const module = renderModule(type),
        ctr = module && module.headless;

  if (!ctr) error('Unrecognized renderer type: ' + type);

  await view.runAsync();
  return initializeRenderer(view, null, null, ctr, scaleFactor, opt)
    .renderAsync(view._scenegraph.root);
}

/**
 * Produce an image URL for the visualization. Depending on the type
 * parameter, the generated URL contains data for either a PNG or SVG image.
 * The URL can be used (for example) to download images of the visualization.
 * This method is asynchronous, returning a Promise instance.
 * @param {string} type - The image type. One of 'svg', 'png' or 'canvas'.
 *   The 'canvas' and 'png' types are synonyms for a PNG image.
 * @return {Promise} - A promise that resolves to an image URL.
 */
async function renderToImageURL(type, scaleFactor) {
  if (type !== RenderType.Canvas && type !== RenderType.SVG && type !== RenderType.PNG) {
    error('Unrecognized image type: ' + type);
  }

  const r = await renderHeadless(this, type, scaleFactor);
  return type === RenderType.SVG
    ? toBlobURL(r.svg(), 'image/svg+xml')
    : r.canvas().toDataURL('image/png');
}

function toBlobURL(data, mime) {
  var blob = new Blob([data], {type: mime});
  return window.URL.createObjectURL(blob);
}

/**
 * Produce a Canvas instance containing a rendered visualization.
 * This method is asynchronous, returning a Promise instance.
 * @return {Promise} - A promise that resolves to a Canvas instance.
 */
async function renderToCanvas(scaleFactor, opt) {
  const r = await renderHeadless(this, RenderType.Canvas, scaleFactor, opt);
  return r.canvas();
}

/**
 * Produce a rendered SVG string of the visualization.
 * This method is asynchronous, returning a Promise instance.
 * @return {Promise} - A promise that resolves to an SVG string.
 */
async function renderToSVG(scaleFactor) {
  const r = await renderHeadless(this, RenderType.SVG, scaleFactor);
  return r.svg();
}

var RawCode = 'RawCode';
var Literal = 'Literal';
var Property = 'Property';
var Identifier$1 = 'Identifier';

var ArrayExpression = 'ArrayExpression';
var BinaryExpression = 'BinaryExpression';
var CallExpression = 'CallExpression';
var ConditionalExpression = 'ConditionalExpression';
var LogicalExpression = 'LogicalExpression';
var MemberExpression = 'MemberExpression';
var ObjectExpression = 'ObjectExpression';
var UnaryExpression = 'UnaryExpression';

function ASTNode(type) {
  this.type = type;
}

ASTNode.prototype.visit = function(visitor) {
  var node = this, c, i, n;

  if (visitor(node)) return 1;

  for (c=children$1(node), i=0, n=c.length; i<n; ++i) {
    if (c[i].visit(visitor)) return 1;
  }
};

function children$1(node) {
  switch (node.type) {
    case ArrayExpression:
      return node.elements;
    case BinaryExpression:
    case LogicalExpression:
      return [node.left, node.right];
    case CallExpression:
      var args = node.arguments.slice();
      args.unshift(node.callee);
      return args;
    case ConditionalExpression:
      return [node.test, node.consequent, node.alternate];
    case MemberExpression:
      return [node.object, node.property];
    case ObjectExpression:
      return node.properties;
    case Property:
      return [node.key, node.value];
    case UnaryExpression:
      return [node.argument];
    case Identifier$1:
    case Literal:
    case RawCode:
    default:
      return [];
  }
}

/*
  The following expression parser is based on Esprima (http://esprima.org/).
  Original header comment and license for Esprima is included here:

  Copyright (C) 2013 Ariya Hidayat <ariya.hidayat@gmail.com>
  Copyright (C) 2013 Thaddee Tyl <thaddee.tyl@gmail.com>
  Copyright (C) 2013 Mathias Bynens <mathias@qiwi.be>
  Copyright (C) 2012 Ariya Hidayat <ariya.hidayat@gmail.com>
  Copyright (C) 2012 Mathias Bynens <mathias@qiwi.be>
  Copyright (C) 2012 Joost-Wim Boekesteijn <joost-wim@boekesteijn.nl>
  Copyright (C) 2012 Kris Kowal <kris.kowal@cixar.com>
  Copyright (C) 2012 Yusuke Suzuki <utatane.tea@gmail.com>
  Copyright (C) 2012 Arpad Borsos <arpad.borsos@googlemail.com>
  Copyright (C) 2011 Ariya Hidayat <ariya.hidayat@gmail.com>

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

var TokenName,
    source$1,
    index,
    length,
    lookahead;

var TokenBooleanLiteral = 1,
    TokenEOF = 2,
    TokenIdentifier = 3,
    TokenKeyword = 4,
    TokenNullLiteral = 5,
    TokenNumericLiteral = 6,
    TokenPunctuator = 7,
    TokenStringLiteral = 8,
    TokenRegularExpression = 9;

TokenName = {};
TokenName[TokenBooleanLiteral] = 'Boolean';
TokenName[TokenEOF] = '<end>';
TokenName[TokenIdentifier] = 'Identifier';
TokenName[TokenKeyword] = 'Keyword';
TokenName[TokenNullLiteral] = 'Null';
TokenName[TokenNumericLiteral] = 'Numeric';
TokenName[TokenPunctuator] = 'Punctuator';
TokenName[TokenStringLiteral] = 'String';
TokenName[TokenRegularExpression] = 'RegularExpression';

var SyntaxArrayExpression = 'ArrayExpression',
    SyntaxBinaryExpression = 'BinaryExpression',
    SyntaxCallExpression = 'CallExpression',
    SyntaxConditionalExpression = 'ConditionalExpression',
    SyntaxIdentifier = 'Identifier',
    SyntaxLiteral = 'Literal',
    SyntaxLogicalExpression = 'LogicalExpression',
    SyntaxMemberExpression = 'MemberExpression',
    SyntaxObjectExpression = 'ObjectExpression',
    SyntaxProperty = 'Property',
    SyntaxUnaryExpression = 'UnaryExpression';

// Error messages should be identical to V8.
var MessageUnexpectedToken = 'Unexpected token %0',
    MessageUnexpectedNumber = 'Unexpected number',
    MessageUnexpectedString = 'Unexpected string',
    MessageUnexpectedIdentifier = 'Unexpected identifier',
    MessageUnexpectedReserved = 'Unexpected reserved word',
    MessageUnexpectedEOS = 'Unexpected end of input',
    MessageInvalidRegExp = 'Invalid regular expression',
    MessageUnterminatedRegExp = 'Invalid regular expression: missing /',
    MessageStrictOctalLiteral = 'Octal literals are not allowed in strict mode.',
    MessageStrictDuplicateProperty = 'Duplicate data property in object literal not allowed in strict mode';

var ILLEGAL = 'ILLEGAL',
    DISABLED = 'Disabled.';

// See also tools/generate-unicode-regex.py.
var RegexNonAsciiIdentifierStart = new RegExp("[\\xAA\\xB5\\xBA\\xC0-\\xD6\\xD8-\\xF6\\xF8-\\u02C1\\u02C6-\\u02D1\\u02E0-\\u02E4\\u02EC\\u02EE\\u0370-\\u0374\\u0376\\u0377\\u037A-\\u037D\\u037F\\u0386\\u0388-\\u038A\\u038C\\u038E-\\u03A1\\u03A3-\\u03F5\\u03F7-\\u0481\\u048A-\\u052F\\u0531-\\u0556\\u0559\\u0561-\\u0587\\u05D0-\\u05EA\\u05F0-\\u05F2\\u0620-\\u064A\\u066E\\u066F\\u0671-\\u06D3\\u06D5\\u06E5\\u06E6\\u06EE\\u06EF\\u06FA-\\u06FC\\u06FF\\u0710\\u0712-\\u072F\\u074D-\\u07A5\\u07B1\\u07CA-\\u07EA\\u07F4\\u07F5\\u07FA\\u0800-\\u0815\\u081A\\u0824\\u0828\\u0840-\\u0858\\u08A0-\\u08B2\\u0904-\\u0939\\u093D\\u0950\\u0958-\\u0961\\u0971-\\u0980\\u0985-\\u098C\\u098F\\u0990\\u0993-\\u09A8\\u09AA-\\u09B0\\u09B2\\u09B6-\\u09B9\\u09BD\\u09CE\\u09DC\\u09DD\\u09DF-\\u09E1\\u09F0\\u09F1\\u0A05-\\u0A0A\\u0A0F\\u0A10\\u0A13-\\u0A28\\u0A2A-\\u0A30\\u0A32\\u0A33\\u0A35\\u0A36\\u0A38\\u0A39\\u0A59-\\u0A5C\\u0A5E\\u0A72-\\u0A74\\u0A85-\\u0A8D\\u0A8F-\\u0A91\\u0A93-\\u0AA8\\u0AAA-\\u0AB0\\u0AB2\\u0AB3\\u0AB5-\\u0AB9\\u0ABD\\u0AD0\\u0AE0\\u0AE1\\u0B05-\\u0B0C\\u0B0F\\u0B10\\u0B13-\\u0B28\\u0B2A-\\u0B30\\u0B32\\u0B33\\u0B35-\\u0B39\\u0B3D\\u0B5C\\u0B5D\\u0B5F-\\u0B61\\u0B71\\u0B83\\u0B85-\\u0B8A\\u0B8E-\\u0B90\\u0B92-\\u0B95\\u0B99\\u0B9A\\u0B9C\\u0B9E\\u0B9F\\u0BA3\\u0BA4\\u0BA8-\\u0BAA\\u0BAE-\\u0BB9\\u0BD0\\u0C05-\\u0C0C\\u0C0E-\\u0C10\\u0C12-\\u0C28\\u0C2A-\\u0C39\\u0C3D\\u0C58\\u0C59\\u0C60\\u0C61\\u0C85-\\u0C8C\\u0C8E-\\u0C90\\u0C92-\\u0CA8\\u0CAA-\\u0CB3\\u0CB5-\\u0CB9\\u0CBD\\u0CDE\\u0CE0\\u0CE1\\u0CF1\\u0CF2\\u0D05-\\u0D0C\\u0D0E-\\u0D10\\u0D12-\\u0D3A\\u0D3D\\u0D4E\\u0D60\\u0D61\\u0D7A-\\u0D7F\\u0D85-\\u0D96\\u0D9A-\\u0DB1\\u0DB3-\\u0DBB\\u0DBD\\u0DC0-\\u0DC6\\u0E01-\\u0E30\\u0E32\\u0E33\\u0E40-\\u0E46\\u0E81\\u0E82\\u0E84\\u0E87\\u0E88\\u0E8A\\u0E8D\\u0E94-\\u0E97\\u0E99-\\u0E9F\\u0EA1-\\u0EA3\\u0EA5\\u0EA7\\u0EAA\\u0EAB\\u0EAD-\\u0EB0\\u0EB2\\u0EB3\\u0EBD\\u0EC0-\\u0EC4\\u0EC6\\u0EDC-\\u0EDF\\u0F00\\u0F40-\\u0F47\\u0F49-\\u0F6C\\u0F88-\\u0F8C\\u1000-\\u102A\\u103F\\u1050-\\u1055\\u105A-\\u105D\\u1061\\u1065\\u1066\\u106E-\\u1070\\u1075-\\u1081\\u108E\\u10A0-\\u10C5\\u10C7\\u10CD\\u10D0-\\u10FA\\u10FC-\\u1248\\u124A-\\u124D\\u1250-\\u1256\\u1258\\u125A-\\u125D\\u1260-\\u1288\\u128A-\\u128D\\u1290-\\u12B0\\u12B2-\\u12B5\\u12B8-\\u12BE\\u12C0\\u12C2-\\u12C5\\u12C8-\\u12D6\\u12D8-\\u1310\\u1312-\\u1315\\u1318-\\u135A\\u1380-\\u138F\\u13A0-\\u13F4\\u1401-\\u166C\\u166F-\\u167F\\u1681-\\u169A\\u16A0-\\u16EA\\u16EE-\\u16F8\\u1700-\\u170C\\u170E-\\u1711\\u1720-\\u1731\\u1740-\\u1751\\u1760-\\u176C\\u176E-\\u1770\\u1780-\\u17B3\\u17D7\\u17DC\\u1820-\\u1877\\u1880-\\u18A8\\u18AA\\u18B0-\\u18F5\\u1900-\\u191E\\u1950-\\u196D\\u1970-\\u1974\\u1980-\\u19AB\\u19C1-\\u19C7\\u1A00-\\u1A16\\u1A20-\\u1A54\\u1AA7\\u1B05-\\u1B33\\u1B45-\\u1B4B\\u1B83-\\u1BA0\\u1BAE\\u1BAF\\u1BBA-\\u1BE5\\u1C00-\\u1C23\\u1C4D-\\u1C4F\\u1C5A-\\u1C7D\\u1CE9-\\u1CEC\\u1CEE-\\u1CF1\\u1CF5\\u1CF6\\u1D00-\\u1DBF\\u1E00-\\u1F15\\u1F18-\\u1F1D\\u1F20-\\u1F45\\u1F48-\\u1F4D\\u1F50-\\u1F57\\u1F59\\u1F5B\\u1F5D\\u1F5F-\\u1F7D\\u1F80-\\u1FB4\\u1FB6-\\u1FBC\\u1FBE\\u1FC2-\\u1FC4\\u1FC6-\\u1FCC\\u1FD0-\\u1FD3\\u1FD6-\\u1FDB\\u1FE0-\\u1FEC\\u1FF2-\\u1FF4\\u1FF6-\\u1FFC\\u2071\\u207F\\u2090-\\u209C\\u2102\\u2107\\u210A-\\u2113\\u2115\\u2119-\\u211D\\u2124\\u2126\\u2128\\u212A-\\u212D\\u212F-\\u2139\\u213C-\\u213F\\u2145-\\u2149\\u214E\\u2160-\\u2188\\u2C00-\\u2C2E\\u2C30-\\u2C5E\\u2C60-\\u2CE4\\u2CEB-\\u2CEE\\u2CF2\\u2CF3\\u2D00-\\u2D25\\u2D27\\u2D2D\\u2D30-\\u2D67\\u2D6F\\u2D80-\\u2D96\\u2DA0-\\u2DA6\\u2DA8-\\u2DAE\\u2DB0-\\u2DB6\\u2DB8-\\u2DBE\\u2DC0-\\u2DC6\\u2DC8-\\u2DCE\\u2DD0-\\u2DD6\\u2DD8-\\u2DDE\\u2E2F\\u3005-\\u3007\\u3021-\\u3029\\u3031-\\u3035\\u3038-\\u303C\\u3041-\\u3096\\u309D-\\u309F\\u30A1-\\u30FA\\u30FC-\\u30FF\\u3105-\\u312D\\u3131-\\u318E\\u31A0-\\u31BA\\u31F0-\\u31FF\\u3400-\\u4DB5\\u4E00-\\u9FCC\\uA000-\\uA48C\\uA4D0-\\uA4FD\\uA500-\\uA60C\\uA610-\\uA61F\\uA62A\\uA62B\\uA640-\\uA66E\\uA67F-\\uA69D\\uA6A0-\\uA6EF\\uA717-\\uA71F\\uA722-\\uA788\\uA78B-\\uA78E\\uA790-\\uA7AD\\uA7B0\\uA7B1\\uA7F7-\\uA801\\uA803-\\uA805\\uA807-\\uA80A\\uA80C-\\uA822\\uA840-\\uA873\\uA882-\\uA8B3\\uA8F2-\\uA8F7\\uA8FB\\uA90A-\\uA925\\uA930-\\uA946\\uA960-\\uA97C\\uA984-\\uA9B2\\uA9CF\\uA9E0-\\uA9E4\\uA9E6-\\uA9EF\\uA9FA-\\uA9FE\\uAA00-\\uAA28\\uAA40-\\uAA42\\uAA44-\\uAA4B\\uAA60-\\uAA76\\uAA7A\\uAA7E-\\uAAAF\\uAAB1\\uAAB5\\uAAB6\\uAAB9-\\uAABD\\uAAC0\\uAAC2\\uAADB-\\uAADD\\uAAE0-\\uAAEA\\uAAF2-\\uAAF4\\uAB01-\\uAB06\\uAB09-\\uAB0E\\uAB11-\\uAB16\\uAB20-\\uAB26\\uAB28-\\uAB2E\\uAB30-\\uAB5A\\uAB5C-\\uAB5F\\uAB64\\uAB65\\uABC0-\\uABE2\\uAC00-\\uD7A3\\uD7B0-\\uD7C6\\uD7CB-\\uD7FB\\uF900-\\uFA6D\\uFA70-\\uFAD9\\uFB00-\\uFB06\\uFB13-\\uFB17\\uFB1D\\uFB1F-\\uFB28\\uFB2A-\\uFB36\\uFB38-\\uFB3C\\uFB3E\\uFB40\\uFB41\\uFB43\\uFB44\\uFB46-\\uFBB1\\uFBD3-\\uFD3D\\uFD50-\\uFD8F\\uFD92-\\uFDC7\\uFDF0-\\uFDFB\\uFE70-\\uFE74\\uFE76-\\uFEFC\\uFF21-\\uFF3A\\uFF41-\\uFF5A\\uFF66-\\uFFBE\\uFFC2-\\uFFC7\\uFFCA-\\uFFCF\\uFFD2-\\uFFD7\\uFFDA-\\uFFDC]"),
    // eslint-disable-next-line no-misleading-character-class
    RegexNonAsciiIdentifierPart = new RegExp("[\\xAA\\xB5\\xBA\\xC0-\\xD6\\xD8-\\xF6\\xF8-\\u02C1\\u02C6-\\u02D1\\u02E0-\\u02E4\\u02EC\\u02EE\\u0300-\\u0374\\u0376\\u0377\\u037A-\\u037D\\u037F\\u0386\\u0388-\\u038A\\u038C\\u038E-\\u03A1\\u03A3-\\u03F5\\u03F7-\\u0481\\u0483-\\u0487\\u048A-\\u052F\\u0531-\\u0556\\u0559\\u0561-\\u0587\\u0591-\\u05BD\\u05BF\\u05C1\\u05C2\\u05C4\\u05C5\\u05C7\\u05D0-\\u05EA\\u05F0-\\u05F2\\u0610-\\u061A\\u0620-\\u0669\\u066E-\\u06D3\\u06D5-\\u06DC\\u06DF-\\u06E8\\u06EA-\\u06FC\\u06FF\\u0710-\\u074A\\u074D-\\u07B1\\u07C0-\\u07F5\\u07FA\\u0800-\\u082D\\u0840-\\u085B\\u08A0-\\u08B2\\u08E4-\\u0963\\u0966-\\u096F\\u0971-\\u0983\\u0985-\\u098C\\u098F\\u0990\\u0993-\\u09A8\\u09AA-\\u09B0\\u09B2\\u09B6-\\u09B9\\u09BC-\\u09C4\\u09C7\\u09C8\\u09CB-\\u09CE\\u09D7\\u09DC\\u09DD\\u09DF-\\u09E3\\u09E6-\\u09F1\\u0A01-\\u0A03\\u0A05-\\u0A0A\\u0A0F\\u0A10\\u0A13-\\u0A28\\u0A2A-\\u0A30\\u0A32\\u0A33\\u0A35\\u0A36\\u0A38\\u0A39\\u0A3C\\u0A3E-\\u0A42\\u0A47\\u0A48\\u0A4B-\\u0A4D\\u0A51\\u0A59-\\u0A5C\\u0A5E\\u0A66-\\u0A75\\u0A81-\\u0A83\\u0A85-\\u0A8D\\u0A8F-\\u0A91\\u0A93-\\u0AA8\\u0AAA-\\u0AB0\\u0AB2\\u0AB3\\u0AB5-\\u0AB9\\u0ABC-\\u0AC5\\u0AC7-\\u0AC9\\u0ACB-\\u0ACD\\u0AD0\\u0AE0-\\u0AE3\\u0AE6-\\u0AEF\\u0B01-\\u0B03\\u0B05-\\u0B0C\\u0B0F\\u0B10\\u0B13-\\u0B28\\u0B2A-\\u0B30\\u0B32\\u0B33\\u0B35-\\u0B39\\u0B3C-\\u0B44\\u0B47\\u0B48\\u0B4B-\\u0B4D\\u0B56\\u0B57\\u0B5C\\u0B5D\\u0B5F-\\u0B63\\u0B66-\\u0B6F\\u0B71\\u0B82\\u0B83\\u0B85-\\u0B8A\\u0B8E-\\u0B90\\u0B92-\\u0B95\\u0B99\\u0B9A\\u0B9C\\u0B9E\\u0B9F\\u0BA3\\u0BA4\\u0BA8-\\u0BAA\\u0BAE-\\u0BB9\\u0BBE-\\u0BC2\\u0BC6-\\u0BC8\\u0BCA-\\u0BCD\\u0BD0\\u0BD7\\u0BE6-\\u0BEF\\u0C00-\\u0C03\\u0C05-\\u0C0C\\u0C0E-\\u0C10\\u0C12-\\u0C28\\u0C2A-\\u0C39\\u0C3D-\\u0C44\\u0C46-\\u0C48\\u0C4A-\\u0C4D\\u0C55\\u0C56\\u0C58\\u0C59\\u0C60-\\u0C63\\u0C66-\\u0C6F\\u0C81-\\u0C83\\u0C85-\\u0C8C\\u0C8E-\\u0C90\\u0C92-\\u0CA8\\u0CAA-\\u0CB3\\u0CB5-\\u0CB9\\u0CBC-\\u0CC4\\u0CC6-\\u0CC8\\u0CCA-\\u0CCD\\u0CD5\\u0CD6\\u0CDE\\u0CE0-\\u0CE3\\u0CE6-\\u0CEF\\u0CF1\\u0CF2\\u0D01-\\u0D03\\u0D05-\\u0D0C\\u0D0E-\\u0D10\\u0D12-\\u0D3A\\u0D3D-\\u0D44\\u0D46-\\u0D48\\u0D4A-\\u0D4E\\u0D57\\u0D60-\\u0D63\\u0D66-\\u0D6F\\u0D7A-\\u0D7F\\u0D82\\u0D83\\u0D85-\\u0D96\\u0D9A-\\u0DB1\\u0DB3-\\u0DBB\\u0DBD\\u0DC0-\\u0DC6\\u0DCA\\u0DCF-\\u0DD4\\u0DD6\\u0DD8-\\u0DDF\\u0DE6-\\u0DEF\\u0DF2\\u0DF3\\u0E01-\\u0E3A\\u0E40-\\u0E4E\\u0E50-\\u0E59\\u0E81\\u0E82\\u0E84\\u0E87\\u0E88\\u0E8A\\u0E8D\\u0E94-\\u0E97\\u0E99-\\u0E9F\\u0EA1-\\u0EA3\\u0EA5\\u0EA7\\u0EAA\\u0EAB\\u0EAD-\\u0EB9\\u0EBB-\\u0EBD\\u0EC0-\\u0EC4\\u0EC6\\u0EC8-\\u0ECD\\u0ED0-\\u0ED9\\u0EDC-\\u0EDF\\u0F00\\u0F18\\u0F19\\u0F20-\\u0F29\\u0F35\\u0F37\\u0F39\\u0F3E-\\u0F47\\u0F49-\\u0F6C\\u0F71-\\u0F84\\u0F86-\\u0F97\\u0F99-\\u0FBC\\u0FC6\\u1000-\\u1049\\u1050-\\u109D\\u10A0-\\u10C5\\u10C7\\u10CD\\u10D0-\\u10FA\\u10FC-\\u1248\\u124A-\\u124D\\u1250-\\u1256\\u1258\\u125A-\\u125D\\u1260-\\u1288\\u128A-\\u128D\\u1290-\\u12B0\\u12B2-\\u12B5\\u12B8-\\u12BE\\u12C0\\u12C2-\\u12C5\\u12C8-\\u12D6\\u12D8-\\u1310\\u1312-\\u1315\\u1318-\\u135A\\u135D-\\u135F\\u1380-\\u138F\\u13A0-\\u13F4\\u1401-\\u166C\\u166F-\\u167F\\u1681-\\u169A\\u16A0-\\u16EA\\u16EE-\\u16F8\\u1700-\\u170C\\u170E-\\u1714\\u1720-\\u1734\\u1740-\\u1753\\u1760-\\u176C\\u176E-\\u1770\\u1772\\u1773\\u1780-\\u17D3\\u17D7\\u17DC\\u17DD\\u17E0-\\u17E9\\u180B-\\u180D\\u1810-\\u1819\\u1820-\\u1877\\u1880-\\u18AA\\u18B0-\\u18F5\\u1900-\\u191E\\u1920-\\u192B\\u1930-\\u193B\\u1946-\\u196D\\u1970-\\u1974\\u1980-\\u19AB\\u19B0-\\u19C9\\u19D0-\\u19D9\\u1A00-\\u1A1B\\u1A20-\\u1A5E\\u1A60-\\u1A7C\\u1A7F-\\u1A89\\u1A90-\\u1A99\\u1AA7\\u1AB0-\\u1ABD\\u1B00-\\u1B4B\\u1B50-\\u1B59\\u1B6B-\\u1B73\\u1B80-\\u1BF3\\u1C00-\\u1C37\\u1C40-\\u1C49\\u1C4D-\\u1C7D\\u1CD0-\\u1CD2\\u1CD4-\\u1CF6\\u1CF8\\u1CF9\\u1D00-\\u1DF5\\u1DFC-\\u1F15\\u1F18-\\u1F1D\\u1F20-\\u1F45\\u1F48-\\u1F4D\\u1F50-\\u1F57\\u1F59\\u1F5B\\u1F5D\\u1F5F-\\u1F7D\\u1F80-\\u1FB4\\u1FB6-\\u1FBC\\u1FBE\\u1FC2-\\u1FC4\\u1FC6-\\u1FCC\\u1FD0-\\u1FD3\\u1FD6-\\u1FDB\\u1FE0-\\u1FEC\\u1FF2-\\u1FF4\\u1FF6-\\u1FFC\\u200C\\u200D\\u203F\\u2040\\u2054\\u2071\\u207F\\u2090-\\u209C\\u20D0-\\u20DC\\u20E1\\u20E5-\\u20F0\\u2102\\u2107\\u210A-\\u2113\\u2115\\u2119-\\u211D\\u2124\\u2126\\u2128\\u212A-\\u212D\\u212F-\\u2139\\u213C-\\u213F\\u2145-\\u2149\\u214E\\u2160-\\u2188\\u2C00-\\u2C2E\\u2C30-\\u2C5E\\u2C60-\\u2CE4\\u2CEB-\\u2CF3\\u2D00-\\u2D25\\u2D27\\u2D2D\\u2D30-\\u2D67\\u2D6F\\u2D7F-\\u2D96\\u2DA0-\\u2DA6\\u2DA8-\\u2DAE\\u2DB0-\\u2DB6\\u2DB8-\\u2DBE\\u2DC0-\\u2DC6\\u2DC8-\\u2DCE\\u2DD0-\\u2DD6\\u2DD8-\\u2DDE\\u2DE0-\\u2DFF\\u2E2F\\u3005-\\u3007\\u3021-\\u302F\\u3031-\\u3035\\u3038-\\u303C\\u3041-\\u3096\\u3099\\u309A\\u309D-\\u309F\\u30A1-\\u30FA\\u30FC-\\u30FF\\u3105-\\u312D\\u3131-\\u318E\\u31A0-\\u31BA\\u31F0-\\u31FF\\u3400-\\u4DB5\\u4E00-\\u9FCC\\uA000-\\uA48C\\uA4D0-\\uA4FD\\uA500-\\uA60C\\uA610-\\uA62B\\uA640-\\uA66F\\uA674-\\uA67D\\uA67F-\\uA69D\\uA69F-\\uA6F1\\uA717-\\uA71F\\uA722-\\uA788\\uA78B-\\uA78E\\uA790-\\uA7AD\\uA7B0\\uA7B1\\uA7F7-\\uA827\\uA840-\\uA873\\uA880-\\uA8C4\\uA8D0-\\uA8D9\\uA8E0-\\uA8F7\\uA8FB\\uA900-\\uA92D\\uA930-\\uA953\\uA960-\\uA97C\\uA980-\\uA9C0\\uA9CF-\\uA9D9\\uA9E0-\\uA9FE\\uAA00-\\uAA36\\uAA40-\\uAA4D\\uAA50-\\uAA59\\uAA60-\\uAA76\\uAA7A-\\uAAC2\\uAADB-\\uAADD\\uAAE0-\\uAAEF\\uAAF2-\\uAAF6\\uAB01-\\uAB06\\uAB09-\\uAB0E\\uAB11-\\uAB16\\uAB20-\\uAB26\\uAB28-\\uAB2E\\uAB30-\\uAB5A\\uAB5C-\\uAB5F\\uAB64\\uAB65\\uABC0-\\uABEA\\uABEC\\uABED\\uABF0-\\uABF9\\uAC00-\\uD7A3\\uD7B0-\\uD7C6\\uD7CB-\\uD7FB\\uF900-\\uFA6D\\uFA70-\\uFAD9\\uFB00-\\uFB06\\uFB13-\\uFB17\\uFB1D-\\uFB28\\uFB2A-\\uFB36\\uFB38-\\uFB3C\\uFB3E\\uFB40\\uFB41\\uFB43\\uFB44\\uFB46-\\uFBB1\\uFBD3-\\uFD3D\\uFD50-\\uFD8F\\uFD92-\\uFDC7\\uFDF0-\\uFDFB\\uFE00-\\uFE0F\\uFE20-\\uFE2D\\uFE33\\uFE34\\uFE4D-\\uFE4F\\uFE70-\\uFE74\\uFE76-\\uFEFC\\uFF10-\\uFF19\\uFF21-\\uFF3A\\uFF3F\\uFF41-\\uFF5A\\uFF66-\\uFFBE\\uFFC2-\\uFFC7\\uFFCA-\\uFFCF\\uFFD2-\\uFFD7\\uFFDA-\\uFFDC]");

// Ensure the condition is true, otherwise throw an error.
// This is only to have a better contract semantic, i.e. another safety net
// to catch a logic error. The condition shall be fulfilled in normal case.
// Do NOT use this to enforce a certain condition on any user input.

function assert(condition, message) {
  /* istanbul ignore next */
  if (!condition) {
    throw new Error('ASSERT: ' + message);
  }
}

function isDecimalDigit(ch) {
  return (ch >= 0x30 && ch <= 0x39); // 0..9
}

function isHexDigit(ch) {
  return '0123456789abcdefABCDEF'.indexOf(ch) >= 0;
}

function isOctalDigit(ch) {
  return '01234567'.indexOf(ch) >= 0;
}

// 7.2 White Space

function isWhiteSpace(ch) {
  return (ch === 0x20) || (ch === 0x09) || (ch === 0x0B) || (ch === 0x0C) || (ch === 0xA0) ||
    (ch >= 0x1680 && [0x1680, 0x180E, 0x2000, 0x2001, 0x2002, 0x2003, 0x2004, 0x2005, 0x2006, 0x2007, 0x2008, 0x2009, 0x200A, 0x202F, 0x205F, 0x3000, 0xFEFF].indexOf(ch) >= 0);
}

// 7.3 Line Terminators

function isLineTerminator(ch) {
  return (ch === 0x0A) || (ch === 0x0D) || (ch === 0x2028) || (ch === 0x2029);
}

// 7.6 Identifier Names and Identifiers

function isIdentifierStart(ch) {
  return (ch === 0x24) || (ch === 0x5F) || // $ (dollar) and _ (underscore)
    (ch >= 0x41 && ch <= 0x5A) || // A..Z
    (ch >= 0x61 && ch <= 0x7A) || // a..z
    (ch === 0x5C) || // \ (backslash)
    ((ch >= 0x80) && RegexNonAsciiIdentifierStart.test(String.fromCharCode(ch)));
}

function isIdentifierPart(ch) {
  return (ch === 0x24) || (ch === 0x5F) || // $ (dollar) and _ (underscore)
    (ch >= 0x41 && ch <= 0x5A) || // A..Z
    (ch >= 0x61 && ch <= 0x7A) || // a..z
    (ch >= 0x30 && ch <= 0x39) || // 0..9
    (ch === 0x5C) || // \ (backslash)
    ((ch >= 0x80) && RegexNonAsciiIdentifierPart.test(String.fromCharCode(ch)));
}

// 7.6.1.1 Keywords

var keywords = {
  'if':1, 'in':1, 'do':1,
  'var':1, 'for':1, 'new':1, 'try':1, 'let':1,
  'this':1, 'else':1, 'case':1, 'void':1, 'with':1, 'enum':1,
  'while':1, 'break':1, 'catch':1, 'throw':1, 'const':1, 'yield':1, 'class':1, 'super':1,
  'return':1, 'typeof':1, 'delete':1, 'switch':1, 'export':1, 'import':1, 'public':1, 'static':1,
  'default':1, 'finally':1, 'extends':1, 'package':1, 'private':1,
  'function':1, 'continue':1, 'debugger':1,
  'interface':1, 'protected':1,
  'instanceof':1, 'implements':1
};

function skipComment() {
  var ch;

  while (index < length) {
    ch = source$1.charCodeAt(index);

    if (isWhiteSpace(ch) || isLineTerminator(ch)) {
      ++index;
    } else {
      break;
    }
  }
}

function scanHexEscape(prefix) {
  var i, len, ch, code = 0;

  len = (prefix === 'u') ? 4 : 2;
  for (i = 0; i < len; ++i) {
    if (index < length && isHexDigit(source$1[index])) {
      ch = source$1[index++];
      code = code * 16 + '0123456789abcdef'.indexOf(ch.toLowerCase());
    } else {
      throwError({}, MessageUnexpectedToken, ILLEGAL);
    }
  }
  return String.fromCharCode(code);
}

function scanUnicodeCodePointEscape() {
  var ch, code, cu1, cu2;

  ch = source$1[index];
  code = 0;

  // At least, one hex digit is required.
  if (ch === '}') {
    throwError({}, MessageUnexpectedToken, ILLEGAL);
  }

  while (index < length) {
    ch = source$1[index++];
    if (!isHexDigit(ch)) {
      break;
    }
    code = code * 16 + '0123456789abcdef'.indexOf(ch.toLowerCase());
  }

  if (code > 0x10FFFF || ch !== '}') {
    throwError({}, MessageUnexpectedToken, ILLEGAL);
  }

  // UTF-16 Encoding
  if (code <= 0xFFFF) {
    return String.fromCharCode(code);
  }
  cu1 = ((code - 0x10000) >> 10) + 0xD800;
  cu2 = ((code - 0x10000) & 1023) + 0xDC00;
  return String.fromCharCode(cu1, cu2);
}

function getEscapedIdentifier() {
  var ch, id;

  ch = source$1.charCodeAt(index++);
  id = String.fromCharCode(ch);

  // '\u' (U+005C, U+0075) denotes an escaped character.
  if (ch === 0x5C) {
    if (source$1.charCodeAt(index) !== 0x75) {
      throwError({}, MessageUnexpectedToken, ILLEGAL);
    }
    ++index;
    ch = scanHexEscape('u');
    if (!ch || ch === '\\' || !isIdentifierStart(ch.charCodeAt(0))) {
      throwError({}, MessageUnexpectedToken, ILLEGAL);
    }
    id = ch;
  }

  while (index < length) {
    ch = source$1.charCodeAt(index);
    if (!isIdentifierPart(ch)) {
      break;
    }
    ++index;
    id += String.fromCharCode(ch);

    // '\u' (U+005C, U+0075) denotes an escaped character.
    if (ch === 0x5C) {
      id = id.substr(0, id.length - 1);
      if (source$1.charCodeAt(index) !== 0x75) {
        throwError({}, MessageUnexpectedToken, ILLEGAL);
      }
      ++index;
      ch = scanHexEscape('u');
      if (!ch || ch === '\\' || !isIdentifierPart(ch.charCodeAt(0))) {
        throwError({}, MessageUnexpectedToken, ILLEGAL);
      }
      id += ch;
    }
  }

  return id;
}

function getIdentifier() {
  var start, ch;

  start = index++;
  while (index < length) {
    ch = source$1.charCodeAt(index);
    if (ch === 0x5C) {
      // Blackslash (U+005C) marks Unicode escape sequence.
      index = start;
      return getEscapedIdentifier();
    }
    if (isIdentifierPart(ch)) {
      ++index;
    } else {
      break;
    }
  }

  return source$1.slice(start, index);
}

function scanIdentifier() {
  var start, id, type;

  start = index;

  // Backslash (U+005C) starts an escaped character.
  id = (source$1.charCodeAt(index) === 0x5C) ? getEscapedIdentifier() : getIdentifier();

  // There is no keyword or literal with only one character.
  // Thus, it must be an identifier.
  if (id.length === 1) {
    type = TokenIdentifier;
  } else if (keywords.hasOwnProperty(id)) { // eslint-disable-line no-prototype-builtins
    type = TokenKeyword;
  } else if (id === 'null') {
    type = TokenNullLiteral;
  } else if (id === 'true' || id === 'false') {
    type = TokenBooleanLiteral;
  } else {
    type = TokenIdentifier;
  }

  return {
    type: type,
    value: id,
    start: start,
    end: index
  };
}

// 7.7 Punctuators

function scanPunctuator() {
  var start = index,
    code = source$1.charCodeAt(index),
    code2,
    ch1 = source$1[index],
    ch2,
    ch3,
    ch4;

  switch (code) {

    // Check for most common single-character punctuators.
    case 0x2E: // . dot
    case 0x28: // ( open bracket
    case 0x29: // ) close bracket
    case 0x3B: // ; semicolon
    case 0x2C: // , comma
    case 0x7B: // { open curly brace
    case 0x7D: // } close curly brace
    case 0x5B: // [
    case 0x5D: // ]
    case 0x3A: // :
    case 0x3F: // ?
    case 0x7E: // ~
      ++index;
      return {
        type: TokenPunctuator,
        value: String.fromCharCode(code),
        start: start,
        end: index
      };

    default:
      code2 = source$1.charCodeAt(index + 1);

      // '=' (U+003D) marks an assignment or comparison operator.
      if (code2 === 0x3D) {
        switch (code) {
          case 0x2B: // +
          case 0x2D: // -
          case 0x2F: // /
          case 0x3C: // <
          case 0x3E: // >
          case 0x5E: // ^
          case 0x7C: // |
          case 0x25: // %
          case 0x26: // &
          case 0x2A: // *
            index += 2;
            return {
              type: TokenPunctuator,
              value: String.fromCharCode(code) + String.fromCharCode(code2),
              start: start,
              end: index
            };

          case 0x21: // !
          case 0x3D: // =
            index += 2;

            // !== and ===
            if (source$1.charCodeAt(index) === 0x3D) {
              ++index;
            }
            return {
              type: TokenPunctuator,
              value: source$1.slice(start, index),
              start: start,
              end: index
            };
        }
      }
  }

  // 4-character punctuator: >>>=

  ch4 = source$1.substr(index, 4);

  if (ch4 === '>>>=') {
    index += 4;
    return {
      type: TokenPunctuator,
      value: ch4,
      start: start,
      end: index
    };
  }

  // 3-character punctuators: === !== >>> <<= >>=

  ch3 = ch4.substr(0, 3);

  if (ch3 === '>>>' || ch3 === '<<=' || ch3 === '>>=') {
    index += 3;
    return {
      type: TokenPunctuator,
      value: ch3,
      start: start,
      end: index
    };
  }

  // Other 2-character punctuators: ++ -- << >> && ||
  ch2 = ch3.substr(0, 2);

  if ((ch1 === ch2[1] && ('+-<>&|'.indexOf(ch1) >= 0)) || ch2 === '=>') {
    index += 2;
    return {
      type: TokenPunctuator,
      value: ch2,
      start: start,
      end: index
    };
  }

  // 1-character punctuators: < > = ! + - * % & | ^ /

  if ('<>=!+-*%&|^/'.indexOf(ch1) >= 0) {
    ++index;
    return {
      type: TokenPunctuator,
      value: ch1,
      start: start,
      end: index
    };
  }

  throwError({}, MessageUnexpectedToken, ILLEGAL);
}

// 7.8.3 Numeric Literals

function scanHexLiteral(start) {
  var number = '';

  while (index < length) {
    if (!isHexDigit(source$1[index])) {
      break;
    }
    number += source$1[index++];
  }

  if (number.length === 0) {
    throwError({}, MessageUnexpectedToken, ILLEGAL);
  }

  if (isIdentifierStart(source$1.charCodeAt(index))) {
    throwError({}, MessageUnexpectedToken, ILLEGAL);
  }

  return {
    type: TokenNumericLiteral,
    value: parseInt('0x' + number, 16),
    start: start,
    end: index
  };
}

function scanOctalLiteral(start) {
  var number = '0' + source$1[index++];
  while (index < length) {
    if (!isOctalDigit(source$1[index])) {
      break;
    }
    number += source$1[index++];
  }

  if (isIdentifierStart(source$1.charCodeAt(index)) || isDecimalDigit(source$1.charCodeAt(index))) {
    throwError({}, MessageUnexpectedToken, ILLEGAL);
  }

  return {
    type: TokenNumericLiteral,
    value: parseInt(number, 8),
    octal: true,
    start: start,
    end: index
  };
}

function scanNumericLiteral() {
  var number, start, ch;

  ch = source$1[index];
  assert(isDecimalDigit(ch.charCodeAt(0)) || (ch === '.'),
    'Numeric literal must start with a decimal digit or a decimal point');

  start = index;
  number = '';
  if (ch !== '.') {
    number = source$1[index++];
    ch = source$1[index];

    // Hex number starts with '0x'.
    // Octal number starts with '0'.
    if (number === '0') {
      if (ch === 'x' || ch === 'X') {
        ++index;
        return scanHexLiteral(start);
      }
      if (isOctalDigit(ch)) {
        return scanOctalLiteral(start);
      }

      // decimal number starts with '0' such as '09' is illegal.
      if (ch && isDecimalDigit(ch.charCodeAt(0))) {
        throwError({}, MessageUnexpectedToken, ILLEGAL);
      }
    }

    while (isDecimalDigit(source$1.charCodeAt(index))) {
      number += source$1[index++];
    }
    ch = source$1[index];
  }

  if (ch === '.') {
    number += source$1[index++];
    while (isDecimalDigit(source$1.charCodeAt(index))) {
      number += source$1[index++];
    }
    ch = source$1[index];
  }

  if (ch === 'e' || ch === 'E') {
    number += source$1[index++];

    ch = source$1[index];
    if (ch === '+' || ch === '-') {
      number += source$1[index++];
    }
    if (isDecimalDigit(source$1.charCodeAt(index))) {
      while (isDecimalDigit(source$1.charCodeAt(index))) {
        number += source$1[index++];
      }
    } else {
      throwError({}, MessageUnexpectedToken, ILLEGAL);
    }
  }

  if (isIdentifierStart(source$1.charCodeAt(index))) {
    throwError({}, MessageUnexpectedToken, ILLEGAL);
  }

  return {
    type: TokenNumericLiteral,
    value: parseFloat(number),
    start: start,
    end: index
  };
}

// 7.8.4 String Literals

function scanStringLiteral() {
  var str = '',
    quote, start, ch, code, octal = false;

  quote = source$1[index];
  assert((quote === '\'' || quote === '"'),
    'String literal must starts with a quote');

  start = index;
  ++index;

  while (index < length) {
    ch = source$1[index++];

    if (ch === quote) {
      quote = '';
      break;
    } else if (ch === '\\') {
      ch = source$1[index++];
      if (!ch || !isLineTerminator(ch.charCodeAt(0))) {
        switch (ch) {
          case 'u':
          case 'x':
            if (source$1[index] === '{') {
              ++index;
              str += scanUnicodeCodePointEscape();
            } else {
              str += scanHexEscape(ch);
            }
            break;
          case 'n':
            str += '\n';
            break;
          case 'r':
            str += '\r';
            break;
          case 't':
            str += '\t';
            break;
          case 'b':
            str += '\b';
            break;
          case 'f':
            str += '\f';
            break;
          case 'v':
            str += '\x0B';
            break;

          default:
            if (isOctalDigit(ch)) {
              code = '01234567'.indexOf(ch);

              // \0 is not octal escape sequence
              if (code !== 0) {
                octal = true;
              }

              if (index < length && isOctalDigit(source$1[index])) {
                octal = true;
                code = code * 8 + '01234567'.indexOf(source$1[index++]);

                // 3 digits are only allowed when string starts
                // with 0, 1, 2, 3
                if ('0123'.indexOf(ch) >= 0 &&
                  index < length &&
                  isOctalDigit(source$1[index])) {
                  code = code * 8 + '01234567'.indexOf(source$1[index++]);
                }
              }
              str += String.fromCharCode(code);
            } else {
              str += ch;
            }
            break;
        }
      } else {
        if (ch === '\r' && source$1[index] === '\n') {
          ++index;
        }
      }
    } else if (isLineTerminator(ch.charCodeAt(0))) {
      break;
    } else {
      str += ch;
    }
  }

  if (quote !== '') {
    throwError({}, MessageUnexpectedToken, ILLEGAL);
  }

  return {
    type: TokenStringLiteral,
    value: str,
    octal: octal,
    start: start,
    end: index
  };
}

function testRegExp(pattern, flags) {
  var tmp = pattern;

  if (flags.indexOf('u') >= 0) {
    // Replace each astral symbol and every Unicode code point
    // escape sequence with a single ASCII symbol to avoid throwing on
    // regular expressions that are only valid in combination with the
    // `/u` flag.
    // Note: replacing with the ASCII symbol `x` might cause false
    // negatives in unlikely scenarios. For example, `[\u{61}-b]` is a
    // perfectly valid pattern that is equivalent to `[a-b]`, but it
    // would be replaced by `[x-b]` which throws an error.
    tmp = tmp
      .replace(/\\u\{([0-9a-fA-F]+)\}/g, function($0, $1) {
        if (parseInt($1, 16) <= 0x10FFFF) {
          return 'x';
        }
        throwError({}, MessageInvalidRegExp);
      })
      .replace(/[\uD800-\uDBFF][\uDC00-\uDFFF]/g, 'x');
  }

  // First, detect invalid regular expressions.
  try {
    new RegExp(tmp);
  } catch (e) {
    throwError({}, MessageInvalidRegExp);
  }

  // Return a regular expression object for this pattern-flag pair, or
  // `null` in case the current environment doesn't support the flags it
  // uses.
  try {
    return new RegExp(pattern, flags);
  } catch (exception) {
    return null;
  }
}

function scanRegExpBody() {
  var ch, str, classMarker, terminated, body;

  ch = source$1[index];
  assert(ch === '/', 'Regular expression literal must start with a slash');
  str = source$1[index++];

  classMarker = false;
  terminated = false;
  while (index < length) {
    ch = source$1[index++];
    str += ch;
    if (ch === '\\') {
      ch = source$1[index++];
      // ECMA-262 7.8.5
      if (isLineTerminator(ch.charCodeAt(0))) {
        throwError({}, MessageUnterminatedRegExp);
      }
      str += ch;
    } else if (isLineTerminator(ch.charCodeAt(0))) {
      throwError({}, MessageUnterminatedRegExp);
    } else if (classMarker) {
      if (ch === ']') {
        classMarker = false;
      }
    } else {
      if (ch === '/') {
        terminated = true;
        break;
      } else if (ch === '[') {
        classMarker = true;
      }
    }
  }

  if (!terminated) {
    throwError({}, MessageUnterminatedRegExp);
  }

  // Exclude leading and trailing slash.
  body = str.substr(1, str.length - 2);
  return {
    value: body,
    literal: str
  };
}

function scanRegExpFlags() {
  var ch, str, flags;

  str = '';
  flags = '';
  while (index < length) {
    ch = source$1[index];
    if (!isIdentifierPart(ch.charCodeAt(0))) {
      break;
    }

    ++index;
    if (ch === '\\' && index < length) {
      throwError({}, MessageUnexpectedToken, ILLEGAL);
    } else {
      flags += ch;
      str += ch;
    }
  }

  if (flags.search(/[^gimuy]/g) >= 0) {
    throwError({}, MessageInvalidRegExp, flags);
  }

  return {
    value: flags,
    literal: str
  };
}

function scanRegExp() {
  var start, body, flags, value;

  lookahead = null;
  skipComment();
  start = index;

  body = scanRegExpBody();
  flags = scanRegExpFlags();
  value = testRegExp(body.value, flags.value);

  return {
    literal: body.literal + flags.literal,
    value: value,
    regex: {
      pattern: body.value,
      flags: flags.value
    },
    start: start,
    end: index
  };
}

function isIdentifierName(token) {
  return token.type === TokenIdentifier ||
    token.type === TokenKeyword ||
    token.type === TokenBooleanLiteral ||
    token.type === TokenNullLiteral;
}

function advance() {
  var ch;

  skipComment();

  if (index >= length) {
    return {
      type: TokenEOF,
      start: index,
      end: index
    };
  }

  ch = source$1.charCodeAt(index);

  if (isIdentifierStart(ch)) {
    return scanIdentifier();
  }

  // Very common: ( and ) and ;
  if (ch === 0x28 || ch === 0x29 || ch === 0x3B) {
    return scanPunctuator();
  }

  // String literal starts with single quote (U+0027) or double quote (U+0022).
  if (ch === 0x27 || ch === 0x22) {
    return scanStringLiteral();
  }


  // Dot (.) U+002E can also start a floating-point number, hence the need
  // to check the next character.
  if (ch === 0x2E) {
    if (isDecimalDigit(source$1.charCodeAt(index + 1))) {
      return scanNumericLiteral();
    }
    return scanPunctuator();
  }

  if (isDecimalDigit(ch)) {
    return scanNumericLiteral();
  }

  return scanPunctuator();
}

function lex() {
  var token;

  token = lookahead;
  index = token.end;

  lookahead = advance();

  index = token.end;

  return token;
}

function peek$1() {
  var pos;

  pos = index;

  lookahead = advance();
  index = pos;
}

function finishArrayExpression(elements) {
  var node = new ASTNode(SyntaxArrayExpression);
  node.elements = elements;
  return node;
}

function finishBinaryExpression(operator, left, right) {
  var node = new ASTNode((operator === '||' || operator === '&&') ? SyntaxLogicalExpression : SyntaxBinaryExpression);
  node.operator = operator;
  node.left = left;
  node.right = right;
  return node;
}

function finishCallExpression(callee, args) {
  var node = new ASTNode(SyntaxCallExpression);
  node.callee = callee;
  node.arguments = args;
  return node;
}

function finishConditionalExpression(test, consequent, alternate) {
  var node = new ASTNode(SyntaxConditionalExpression);
  node.test = test;
  node.consequent = consequent;
  node.alternate = alternate;
  return node;
}

function finishIdentifier(name) {
  var node = new ASTNode(SyntaxIdentifier);
  node.name = name;
  return node;
}

function finishLiteral(token) {
  var node = new ASTNode(SyntaxLiteral);
  node.value = token.value;
  node.raw = source$1.slice(token.start, token.end);
  if (token.regex) {
    if (node.raw === '//') {
      node.raw = '/(?:)/';
    }
    node.regex = token.regex;
  }
  return node;
}

function finishMemberExpression(accessor, object, property) {
  var node = new ASTNode(SyntaxMemberExpression);
  node.computed = accessor === '[';
  node.object = object;
  node.property = property;
  if (!node.computed) property.member = true;
  return node;
}

function finishObjectExpression(properties) {
  var node = new ASTNode(SyntaxObjectExpression);
  node.properties = properties;
  return node;
}

function finishProperty(kind, key, value) {
  var node = new ASTNode(SyntaxProperty);
  node.key = key;
  node.value = value;
  node.kind = kind;
  return node;
}

function finishUnaryExpression(operator, argument) {
  var node = new ASTNode(SyntaxUnaryExpression);
  node.operator = operator;
  node.argument = argument;
  node.prefix = true;
  return node;
}

// Throw an exception

function throwError(token, messageFormat) {
  var error,
    args = Array.prototype.slice.call(arguments, 2),
    msg = messageFormat.replace(
      /%(\d)/g,
      function(whole, index) {
        assert(index < args.length, 'Message reference must be in range');
        return args[index];
      }
    );


  error = new Error(msg);
  error.index = index;
  error.description = msg;
  throw error;
}

// Throw an exception because of the token.

function throwUnexpected(token) {
  if (token.type === TokenEOF) {
    throwError(token, MessageUnexpectedEOS);
  }

  if (token.type === TokenNumericLiteral) {
    throwError(token, MessageUnexpectedNumber);
  }

  if (token.type === TokenStringLiteral) {
    throwError(token, MessageUnexpectedString);
  }

  if (token.type === TokenIdentifier) {
    throwError(token, MessageUnexpectedIdentifier);
  }

  if (token.type === TokenKeyword) {
    throwError(token, MessageUnexpectedReserved);
  }

  // BooleanLiteral, NullLiteral, or Punctuator.
  throwError(token, MessageUnexpectedToken, token.value);
}

// Expect the next token to match the specified punctuator.
// If not, an exception will be thrown.

function expect(value) {
  var token = lex();
  if (token.type !== TokenPunctuator || token.value !== value) {
    throwUnexpected(token);
  }
}

// Return true if the next token matches the specified punctuator.

function match(value) {
  return lookahead.type === TokenPunctuator && lookahead.value === value;
}

// Return true if the next token matches the specified keyword

function matchKeyword(keyword) {
  return lookahead.type === TokenKeyword && lookahead.value === keyword;
}

// 11.1.4 Array Initialiser

function parseArrayInitialiser() {
  var elements = [];

  index = lookahead.start;
  expect('[');

  while (!match(']')) {
    if (match(',')) {
      lex();
      elements.push(null);
    } else {
      elements.push(parseConditionalExpression());

      if (!match(']')) {
        expect(',');
      }
    }
  }

  lex();

  return finishArrayExpression(elements);
}

// 11.1.5 Object Initialiser

function parseObjectPropertyKey() {
  var token;

  index = lookahead.start;
  token = lex();

  // Note: This function is called only from parseObjectProperty(), where
  // EOF and Punctuator tokens are already filtered out.

  if (token.type === TokenStringLiteral || token.type === TokenNumericLiteral) {
    if (token.octal) {
      throwError(token, MessageStrictOctalLiteral);
    }
    return finishLiteral(token);
  }

  return finishIdentifier(token.value);
}

function parseObjectProperty() {
  var token, key, id, value;

  index = lookahead.start;
  token = lookahead;

  if (token.type === TokenIdentifier) {
    id = parseObjectPropertyKey();
    expect(':');
    value = parseConditionalExpression();
    return finishProperty('init', id, value);
  }
  if (token.type === TokenEOF || token.type === TokenPunctuator) {
    throwUnexpected(token);
  } else {
    key = parseObjectPropertyKey();
    expect(':');
    value = parseConditionalExpression();
    return finishProperty('init', key, value);
  }
}

function parseObjectInitialiser() {
  var properties = [],
    property, name, key, map = {},
    toString = String;

  index = lookahead.start;
  expect('{');

  while (!match('}')) {
    property = parseObjectProperty();

    if (property.key.type === SyntaxIdentifier) {
      name = property.key.name;
    } else {
      name = toString(property.key.value);
    }

    key = '$' + name;
    if (Object.prototype.hasOwnProperty.call(map, key)) {
      throwError({}, MessageStrictDuplicateProperty);
    } else {
      map[key] = true;
    }

    properties.push(property);

    if (!match('}')) {
      expect(',');
    }
  }

  expect('}');

  return finishObjectExpression(properties);
}

// 11.1.6 The Grouping Operator

function parseGroupExpression() {
  var expr;

  expect('(');

  expr = parseExpression();

  expect(')');

  return expr;
}


// 11.1 Primary Expressions

var legalKeywords = {
  "if": 1,
  "this": 1
};

function parsePrimaryExpression() {
  var type, token, expr;

  if (match('(')) {
    return parseGroupExpression();
  }

  if (match('[')) {
    return parseArrayInitialiser();
  }

  if (match('{')) {
    return parseObjectInitialiser();
  }

  type = lookahead.type;
  index = lookahead.start;


  if (type === TokenIdentifier || legalKeywords[lookahead.value]) {
    expr = finishIdentifier(lex().value);
  } else if (type === TokenStringLiteral || type === TokenNumericLiteral) {
    if (lookahead.octal) {
      throwError(lookahead, MessageStrictOctalLiteral);
    }
    expr = finishLiteral(lex());
  } else if (type === TokenKeyword) {
    throw new Error(DISABLED);
  } else if (type === TokenBooleanLiteral) {
    token = lex();
    token.value = (token.value === 'true');
    expr = finishLiteral(token);
  } else if (type === TokenNullLiteral) {
    token = lex();
    token.value = null;
    expr = finishLiteral(token);
  } else if (match('/') || match('/=')) {
    expr = finishLiteral(scanRegExp());
    peek$1();
  } else {
    throwUnexpected(lex());
  }

  return expr;
}

// 11.2 Left-Hand-Side Expressions

function parseArguments() {
  var args = [];

  expect('(');

  if (!match(')')) {
    while (index < length) {
      args.push(parseConditionalExpression());
      if (match(')')) {
        break;
      }
      expect(',');
    }
  }

  expect(')');

  return args;
}

function parseNonComputedProperty() {
  var token;
  index = lookahead.start;
  token = lex();

  if (!isIdentifierName(token)) {
    throwUnexpected(token);
  }

  return finishIdentifier(token.value);
}

function parseNonComputedMember() {
  expect('.');

  return parseNonComputedProperty();
}

function parseComputedMember() {
  var expr;

  expect('[');

  expr = parseExpression();

  expect(']');

  return expr;
}

function parseLeftHandSideExpressionAllowCall() {
  var expr, args, property;

  expr = parsePrimaryExpression();

  for (;;) {
    if (match('.')) {
      property = parseNonComputedMember();
      expr = finishMemberExpression('.', expr, property);
    } else if (match('(')) {
      args = parseArguments();
      expr = finishCallExpression(expr, args);
    } else if (match('[')) {
      property = parseComputedMember();
      expr = finishMemberExpression('[', expr, property);
    } else {
      break;
    }
  }

  return expr;
}

// 11.3 Postfix Expressions

function parsePostfixExpression() {
  var expr = parseLeftHandSideExpressionAllowCall();

  if (lookahead.type === TokenPunctuator) {
    if ((match('++') || match('--'))) {
      throw new Error(DISABLED);
    }
  }

  return expr;
}

// 11.4 Unary Operators

function parseUnaryExpression() {
  var token, expr;

  if (lookahead.type !== TokenPunctuator && lookahead.type !== TokenKeyword) {
    expr = parsePostfixExpression();
  } else if (match('++') || match('--')) {
    throw new Error(DISABLED);
  } else if (match('+') || match('-') || match('~') || match('!')) {
    token = lex();
    expr = parseUnaryExpression();
    expr = finishUnaryExpression(token.value, expr);
  } else if (matchKeyword('delete') || matchKeyword('void') || matchKeyword('typeof')) {
    throw new Error(DISABLED);
  } else {
    expr = parsePostfixExpression();
  }

  return expr;
}

function binaryPrecedence(token) {
  var prec = 0;

  if (token.type !== TokenPunctuator && token.type !== TokenKeyword) {
    return 0;
  }

  switch (token.value) {
    case '||':
      prec = 1;
      break;

    case '&&':
      prec = 2;
      break;

    case '|':
      prec = 3;
      break;

    case '^':
      prec = 4;
      break;

    case '&':
      prec = 5;
      break;

    case '==':
    case '!=':
    case '===':
    case '!==':
      prec = 6;
      break;

    case '<':
    case '>':
    case '<=':
    case '>=':
    case 'instanceof':
    case 'in':
      prec = 7;
      break;

    case '<<':
    case '>>':
    case '>>>':
      prec = 8;
      break;

    case '+':
    case '-':
      prec = 9;
      break;

    case '*':
    case '/':
    case '%':
      prec = 11;
      break;
  }

  return prec;
}

// 11.5 Multiplicative Operators
// 11.6 Additive Operators
// 11.7 Bitwise Shift Operators
// 11.8 Relational Operators
// 11.9 Equality Operators
// 11.10 Binary Bitwise Operators
// 11.11 Binary Logical Operators

function parseBinaryExpression() {
  var marker, markers, expr, token, prec, stack, right, operator, left, i;

  marker = lookahead;
  left = parseUnaryExpression();

  token = lookahead;
  prec = binaryPrecedence(token);
  if (prec === 0) {
    return left;
  }
  token.prec = prec;
  lex();

  markers = [marker, lookahead];
  right = parseUnaryExpression();

  stack = [left, token, right];

  while ((prec = binaryPrecedence(lookahead)) > 0) {

    // Reduce: make a binary expression from the three topmost entries.
    while ((stack.length > 2) && (prec <= stack[stack.length - 2].prec)) {
      right = stack.pop();
      operator = stack.pop().value;
      left = stack.pop();
      markers.pop();
      expr = finishBinaryExpression(operator, left, right);
      stack.push(expr);
    }

    // Shift.
    token = lex();
    token.prec = prec;
    stack.push(token);
    markers.push(lookahead);
    expr = parseUnaryExpression();
    stack.push(expr);
  }

  // Final reduce to clean-up the stack.
  i = stack.length - 1;
  expr = stack[i];
  markers.pop();
  while (i > 1) {
    markers.pop();
    expr = finishBinaryExpression(stack[i - 1].value, stack[i - 2], expr);
    i -= 2;
  }

  return expr;
}

// 11.12 Conditional Operator

function parseConditionalExpression() {
  var expr, consequent, alternate;

  expr = parseBinaryExpression();

  if (match('?')) {
    lex();
    consequent = parseConditionalExpression();
    expect(':');
    alternate = parseConditionalExpression();

    expr = finishConditionalExpression(expr, consequent, alternate);
  }

  return expr;
}

// 11.14 Comma Operator

function parseExpression() {
  var expr = parseConditionalExpression();

  if (match(',')) {
    throw new Error(DISABLED); // no sequence expressions
  }

  return expr;
}

function parse$3(code) {
  source$1 = code;
  index = 0;
  length = source$1.length;
  lookahead = null;

  peek$1();

  var expr = parseExpression();

  if (lookahead.type !== TokenEOF) {
    throw new Error("Unexpect token after expression.");
  }
  return expr;
}

var constants = {
  NaN:       'NaN',
  E:         'Math.E',
  LN2:       'Math.LN2',
  LN10:      'Math.LN10',
  LOG2E:     'Math.LOG2E',
  LOG10E:    'Math.LOG10E',
  PI:        'Math.PI',
  SQRT1_2:   'Math.SQRT1_2',
  SQRT2:     'Math.SQRT2',
  MIN_VALUE: 'Number.MIN_VALUE',
  MAX_VALUE: 'Number.MAX_VALUE'
};

function functions(codegen) {

  function fncall(name, args, cast, type) {
    var obj = codegen(args[0]);
    if (cast) {
      obj = cast + '(' + obj + ')';
      if (cast.lastIndexOf('new ', 0) === 0) obj = '(' + obj + ')';
    }
    return obj + '.' + name + (type < 0 ? '' : type === 0 ?
      '()' :
      '(' + args.slice(1).map(codegen).join(',') + ')');
  }

  function fn(name, cast, type) {
    return function(args) {
      return fncall(name, args, cast, type);
    };
  }

  var DATE = 'new Date',
      STRING = 'String',
      REGEXP = 'RegExp';

  return {
    // MATH functions
    isNaN:    'Number.isNaN',
    isFinite: 'Number.isFinite',
    abs:      'Math.abs',
    acos:     'Math.acos',
    asin:     'Math.asin',
    atan:     'Math.atan',
    atan2:    'Math.atan2',
    ceil:     'Math.ceil',
    cos:      'Math.cos',
    exp:      'Math.exp',
    floor:    'Math.floor',
    log:      'Math.log',
    max:      'Math.max',
    min:      'Math.min',
    pow:      'Math.pow',
    random:   'Math.random',
    round:    'Math.round',
    sin:      'Math.sin',
    sqrt:     'Math.sqrt',
    tan:      'Math.tan',

    clamp: function(args) {
      if (args.length < 3) error('Missing arguments to clamp function.');
      if (args.length > 3) error('Too many arguments to clamp function.');
      var a = args.map(codegen);
      return 'Math.max('+a[1]+', Math.min('+a[2]+','+a[0]+'))';
    },

    // DATE functions
    now:             'Date.now',
    utc:             'Date.UTC',
    datetime:        DATE,
    date:            fn('getDate', DATE, 0),
    day:             fn('getDay', DATE, 0),
    year:            fn('getFullYear', DATE, 0),
    month:           fn('getMonth', DATE, 0),
    hours:           fn('getHours', DATE, 0),
    minutes:         fn('getMinutes', DATE, 0),
    seconds:         fn('getSeconds', DATE, 0),
    milliseconds:    fn('getMilliseconds', DATE, 0),
    time:            fn('getTime', DATE, 0),
    timezoneoffset:  fn('getTimezoneOffset', DATE, 0),
    utcdate:         fn('getUTCDate', DATE, 0),
    utcday:          fn('getUTCDay', DATE, 0),
    utcyear:         fn('getUTCFullYear', DATE, 0),
    utcmonth:        fn('getUTCMonth', DATE, 0),
    utchours:        fn('getUTCHours', DATE, 0),
    utcminutes:      fn('getUTCMinutes', DATE, 0),
    utcseconds:      fn('getUTCSeconds', DATE, 0),
    utcmilliseconds: fn('getUTCMilliseconds', DATE, 0),

    // sequence functions
    length:      fn('length', null, -1),
    join:        fn('join', null),
    indexof:     fn('indexOf', null),
    lastindexof: fn('lastIndexOf', null),
    slice:       fn('slice', null),

    reverse: function(args) {
      return '('+codegen(args[0])+').slice().reverse()';
    },

    // STRING functions
    parseFloat:  'parseFloat',
    parseInt:    'parseInt',
    upper:       fn('toUpperCase', STRING, 0),
    lower:       fn('toLowerCase', STRING, 0),
    substring:   fn('substring', STRING),
    split:       fn('split', STRING),
    replace:     fn('replace', STRING),
    trim:        fn('trim', STRING, 0),

    // REGEXP functions
    regexp:  REGEXP,
    test:    fn('test', REGEXP),

    // Control Flow functions
    if: function(args) {
        if (args.length < 3) error('Missing arguments to if function.');
        if (args.length > 3) error('Too many arguments to if function.');
        var a = args.map(codegen);
        return '('+a[0]+'?'+a[1]+':'+a[2]+')';
      }
  };
}

function stripQuotes(s) {
  var n = s && s.length - 1;
  return n && (
      (s[0]==='"' && s[n]==='"') ||
      (s[0]==='\'' && s[n]==='\'')
    ) ? s.slice(1, -1) : s;
}

function codegen(opt) {
  opt = opt || {};

  var whitelist = opt.whitelist ? toSet(opt.whitelist) : {},
      blacklist = opt.blacklist ? toSet(opt.blacklist) : {},
      constants$1 = opt.constants || constants,
      functions$1 = (opt.functions || functions)(visit),
      globalvar = opt.globalvar,
      fieldvar = opt.fieldvar,
      globals = {},
      fields = {},
      memberDepth = 0;

  var outputGlobal = isFunction(globalvar)
    ? globalvar
    : function (id) { return globalvar + '["' + id + '"]'; };

  function visit(ast) {
    if (isString(ast)) return ast;
    var generator = Generators[ast.type];
    if (generator == null) error('Unsupported type: ' + ast.type);
    return generator(ast);
  }

  var Generators = {
    Literal: function(n) {
        return n.raw;
      },

    Identifier: function(n) {
      var id = n.name;
      if (memberDepth > 0) {
        return id;
      } else if (hasOwnProperty(blacklist, id)) {
        return error('Illegal identifier: ' + id);
      } else if (hasOwnProperty(constants$1, id)) {
        return constants$1[id];
      } else if (hasOwnProperty(whitelist, id)) {
        return id;
      } else {
        globals[id] = 1;
        return outputGlobal(id);
      }
    },

    MemberExpression: function(n) {
        var d = !n.computed;
        var o = visit(n.object);
        if (d) memberDepth += 1;
        var p = visit(n.property);
        if (o === fieldvar) {
          // strip quotes to sanitize field name (#1653)
          fields[stripQuotes(p)] = 1;
        }
        if (d) memberDepth -= 1;
        return o + (d ? '.'+p : '['+p+']');
      },

    CallExpression: function(n) {
        if (n.callee.type !== 'Identifier') {
          error('Illegal callee type: ' + n.callee.type);
        }
        var callee = n.callee.name;
        var args = n.arguments;
        var fn = hasOwnProperty(functions$1, callee) && functions$1[callee];
        if (!fn) error('Unrecognized function: ' + callee);
        return isFunction(fn)
          ? fn(args)
          : fn + '(' + args.map(visit).join(',') + ')';
      },

    ArrayExpression: function(n) {
        return '[' + n.elements.map(visit).join(',') + ']';
      },

    BinaryExpression: function(n) {
        return '(' + visit(n.left) + n.operator + visit(n.right) + ')';
      },

    UnaryExpression: function(n) {
        return '(' + n.operator + visit(n.argument) + ')';
      },

    ConditionalExpression: function(n) {
        return '(' + visit(n.test) +
          '?' + visit(n.consequent) +
          ':' + visit(n.alternate) +
          ')';
      },

    LogicalExpression: function(n) {
        return '(' + visit(n.left) + n.operator + visit(n.right) + ')';
      },

    ObjectExpression: function(n) {
        return '{' + n.properties.map(visit).join(',') + '}';
      },

    Property: function(n) {
        memberDepth += 1;
        var k = visit(n.key);
        memberDepth -= 1;
        return k + ':' + visit(n.value);
      }
  };

  function codegen(ast) {
    var result = {
      code:    visit(ast),
      globals: Object.keys(globals),
      fields:  Object.keys(fields)
    };
    globals = {};
    fields = {};
    return result;
  }

  codegen.functions = functions$1;
  codegen.constants = constants$1;

  return codegen;
}

const Intersect = 'intersect';
const Union = 'union';
const VlMulti = 'vlMulti';
const Or = 'or';
const And = 'and';

var TYPE_ENUM = 'E',
    TYPE_RANGE_INC = 'R',
    TYPE_RANGE_EXC = 'R-E',
    TYPE_RANGE_LE = 'R-LE',
    TYPE_RANGE_RE = 'R-RE',
    UNIT_INDEX = 'index:unit';

// TODO: revisit date coercion?
function testPoint(datum, entry) {
  var fields = entry.fields,
      values = entry.values,
      n = fields.length,
      i = 0, dval, f;

  for (; i<n; ++i) {
    f = fields[i];
    f.getter = field.getter || field(f.field);
    dval = f.getter(datum);

    if (isDate(dval)) dval = toNumber(dval);
    if (isDate(values[i])) values[i] = toNumber(values[i]);
    if (isDate(values[i][0])) values[i] = values[i].map(toNumber);

    if (f.type === TYPE_ENUM) {
      // Enumerated fields can either specify individual values (single/multi selections)
      // or an array of values (interval selections).
      if(isArray(values[i]) ? values[i].indexOf(dval) < 0 : dval !== values[i]) {
        return false;
      }
    } else {
      if (f.type === TYPE_RANGE_INC) {
        if (!inrange(dval, values[i])) return false;
      } else if (f.type === TYPE_RANGE_RE) {
        // Discrete selection of bins test within the range [bin_start, bin_end).
        if (!inrange(dval, values[i], true, false)) return false;
      } else if (f.type === TYPE_RANGE_EXC) { // 'R-E'/'R-LE' included for completeness.
        if (!inrange(dval, values[i], false, false)) return false;
      } else if (f.type === TYPE_RANGE_LE) {
        if (!inrange(dval, values[i], false, true)) return false;
      }
    }
  }

  return true;
}

/**
 * Tests if a tuple is contained within an interactive selection.
 * @param {string} name - The name of the data set representing the selection.
 *  Tuples in the dataset are of the form
 *  {unit: string, fields: array<fielddef>, values: array<*>}.
 *  Fielddef is of the form
 *  {field: string, channel: string, type: 'E' | 'R'} where
 *  'type' identifies whether tuples in the dataset enumerate
 *  values for the field, or specify a continuous range.
 * @param {object} datum - The tuple to test for inclusion.
 * @param {string} op - The set operation for combining selections.
 *   One of 'intersect' or 'union' (default).
 * @return {boolean} - True if the datum is in the selection, false otherwise.
 */
function selectionTest(name, datum, op) {
  var data = this.context.data[name],
      entries = data ? data.values.value : [],
      unitIdx = data ? data[UNIT_INDEX] && data[UNIT_INDEX].value : undefined,
      intersect = op === Intersect,
      n = entries.length,
      i = 0,
      entry, miss, count, unit, b;

  for (; i<n; ++i) {
    entry = entries[i];

    if (unitIdx && intersect) {
      // multi selections union within the same unit and intersect across units.
      miss = miss || {};
      count = miss[unit=entry.unit] || 0;

      // if we've already matched this unit, skip.
      if (count === -1) continue;

      b = testPoint(datum, entry);
      miss[unit] = b ? -1 : ++count;

      // if we match and there are no other units return true
      // if we've missed against all tuples in this unit return false
      if (b && unitIdx.size === 1) return true;
      if (!b && count === unitIdx.get(unit).count) return false;
    } else {
      b = testPoint(datum, entry);

      // if we find a miss and we do require intersection return false
      // if we find a match and we don't require intersection return true
      if (intersect ^ b) return b;
    }
  }

  // if intersecting and we made it here, then we saw no misses
  // if not intersecting, then we saw no matches
  // if no active selections, return false
  return n && intersect;
}

/**
 * Resolves selection for use as a scale domain or reads via the API.
 * @param {string} name - The name of the dataset representing the selection
 * @param {string} [op='union'] - The set operation for combining selections.
 *                 One of 'intersect' or 'union' (default).
 * @returns {object} An object of selected fields and values.
 */
function selectionResolve(name, op, isMulti) {
  var data = this.context.data[name],
    entries = data ? data.values.value : [],
    resolved = {}, multiRes = {}, types = {},
    entry, fields, values, unit, field, res, resUnit, type, union,
    n = entries.length, i = 0, j, m;

  // First union all entries within the same unit.
  for (; i < n; ++i) {
    entry = entries[i];
    unit = entry.unit;
    fields = entry.fields;
    values = entry.values;

    for (j = 0, m = fields.length; j < m; ++j) {
      field = fields[j];
      res = resolved[field.field] || (resolved[field.field] = {});
      resUnit = res[unit] || (res[unit] = []);
      types[field.field] = type = field.type.charAt(0);
      union = ops[type + '_union'];
      res[unit] = union(resUnit, array(values[j]));
    }

    // If the same multi-selection is repeated over views and projected over
    // an encoding, it may operate over different fields making it especially
    // tricky to reliably resolve it. At best, we can de-dupe identical entries
    // but doing so may be more computationally expensive than it is worth.
    // Instead, for now, we simply transform our store representation into
    // a more human-friendly one.
    if (isMulti) {
      resUnit = multiRes[unit] || (multiRes[unit] = []);
      resUnit.push(array(values).reduce((obj, curr, j) => (obj[fields[j].field] = curr, obj), {}));
    }
  }

  // Then resolve fields across units as per the op.
  op = op || Union;
  Object.keys(resolved).forEach(function (field) {
    resolved[field] = Object.keys(resolved[field])
      .map(unit => resolved[field][unit])
      .reduce((acc, curr) => acc === undefined ? curr : ops[types[field] + '_' + op](acc, curr));
  });

  entries = Object.keys(multiRes);
  if (isMulti && entries.length) {
    resolved[VlMulti] = op === Union
      ? {[Or]: entries.reduce((acc, k) => (acc.push.apply(acc, multiRes[k]), acc), [])}
      : {[And]: entries.map(k => ({[Or]: multiRes[k]}))};
  }

  return resolved;
}

var ops = {
  E_union: function(base, value) {
    if (!base.length) return value;

    var i = 0, n = value.length;
    for (; i<n; ++i) if (base.indexOf(value[i]) < 0) base.push(value[i]);
    return base;
  },

  E_intersect: function(base, value) {
    return !base.length ? value :
      base.filter(function (v) { return value.indexOf(v) >= 0; });
  },

  R_union: function(base, value) {
    var lo = toNumber(value[0]), hi = toNumber(value[1]);
    if (lo > hi) {
      lo = value[1];
      hi = value[0];
    }

    if (!base.length) return [lo, hi];
    if (base[0] > lo) base[0] = lo;
    if (base[1] < hi) base[1] = hi;
    return base;
  },

  R_intersect: function(base, value) {
    var lo = toNumber(value[0]), hi = toNumber(value[1]);
    if (lo > hi) {
      lo = value[1];
      hi = value[0];
    }

    if (!base.length) return [lo, hi];
    if (hi < base[0] || base[1] < lo) {
      return [];
    } else {
      if (base[0] < lo) base[0] = lo;
      if (base[1] > hi) base[1] = hi;
    }
    return base;
  }
};

const DataPrefix = ':',
      IndexPrefix = '@';

function selectionVisitor(name, args, scope, params) {
  if (args[0].type !== Literal) error('First argument to selection functions must be a string literal.');

  const data = args[0].value,
        op = args.length >= 2 && peek(args).value,
        field = 'unit',
        indexName = IndexPrefix + field,
        dataName = DataPrefix + data;

  // eslint-disable-next-line no-prototype-builtins
  if (op === Intersect && !hasOwnProperty(params, indexName)) {
    params[indexName] = scope.getData(data).indataRef(scope, field);
  }

  // eslint-disable-next-line no-prototype-builtins
  if (!hasOwnProperty(params, dataName)) {
    params[dataName] = scope.getData(data).tuplesRef();
  }
}

// https://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef
function channel_luminance_value(channelValue) {
  const val = channelValue / 255;
  if (val <= 0.03928) {
    return val / 12.92;
  }
  return Math.pow((val + 0.055) / 1.055, 2.4);
}

function luminance(color) {
  const c = rgb(color),
        r = channel_luminance_value(c.r),
        g = channel_luminance_value(c.g),
        b = channel_luminance_value(c.b);
  return 0.2126 * r + 0.7152 * g + 0.0722 * b;
}

// https://www.w3.org/TR/2008/REC-WCAG20-20081211/#contrast-ratiodef
function contrast(color1, color2) {
  const lum1 = luminance(color1),
        lum2 = luminance(color2),
        lumL = Math.max(lum1, lum2),
        lumD = Math.min(lum1, lum2);
  return (lumL + 0.05) / (lumD + 0.05);
}

function data$1(name) {
  const data = this.context.data[name];
  return data ? data.values.value : [];
}

function indata(name, field, value) {
  const index = this.context.data[name]['index:' + field],
        entry = index ? index.value.get(value) : undefined;
  return entry ? entry.count : entry;
}

function setdata(name, tuples) {
  const df = this.context.dataflow,
        data = this.context.data[name],
        input = data.input;

  df.pulse(input, df.changeset().remove(truthy).insert(tuples));
  return 1;
}

function encode$1(item, name, retval) {
  if (item) {
    const df = this.context.dataflow,
          target = item.mark.source;
    df.pulse(target, df.changeset().encode(item, name));
  }
  return retval !== undefined ? retval : item;
}

const formatCache = {};

function formatter$1(type, method, specifier) {
  let k = type + ':' + specifier,
      e = formatCache[k];
  if (!e || e[0] !== method) {
    formatCache[k] = (e = [method, method(specifier)]);
  }
  return e[1];
}

function format$1(_, specifier) {
  return formatter$1('format', format$2, specifier)(_);
}

function timeFormat$1(_, specifier) {
  return formatter$1('timeFormat', timeFormat, specifier)(_);
}

function utcFormat$1(_, specifier) {
  return formatter$1('utcFormat', utcFormat, specifier)(_);
}

function timeParse(_, specifier) {
  return formatter$1('timeParse', timeParse$1, specifier)(_);
}

function utcParse(_, specifier) {
  return formatter$1('utcParse', utcParse$1, specifier)(_);
}

var dateObj = new Date(2000, 0, 1);

function time$1(month, day, specifier) {
  if (!Number.isInteger(month) || !Number.isInteger(day)) return '';
  dateObj.setYear(2000);
  dateObj.setMonth(month);
  dateObj.setDate(day);
  return timeFormat$1(dateObj, specifier);
}

function monthFormat(month) {
  return time$1(month, 1, '%B');
}

function monthAbbrevFormat(month) {
  return time$1(month, 1, '%b');
}

function dayFormat(day) {
  return time$1(0, 2 + day, '%A');
}

function dayAbbrevFormat(day) {
  return time$1(0, 2 + day, '%a');
}

function getScale(name, ctx) {
  let s;
  return isFunction(name) ? name
    : isString(name) ? (s = ctx.scales[name]) && s.value
    : undefined;
}

function range$1(name, group) {
  const s = getScale(name, (group || this).context);
  return s && s.range ? s.range() : [];
}

function domain(name, group) {
  const s = getScale(name, (group || this).context);
  return s ? s.domain() : [];
}

function bandwidth(name, group) {
  const s = getScale(name, (group || this).context);
  return s && s.bandwidth ? s.bandwidth() : 0;
}

function bandspace(count, paddingInner, paddingOuter) {
  return bandSpace(count || 0, paddingInner || 0, paddingOuter || 0);
}

function copy$2(name, group) {
  const s = getScale(name, (group || this).context);
  return s ? s.copy() : undefined;
}

function scale$3(name, value, group) {
  const s = getScale(name, (group || this).context);
  return s && value !== undefined ? s(value) : undefined;
}

function invert(name, range, group) {
  const s = getScale(name, (group || this).context);
  return !s ? undefined
    : isArray(range) ? (s.invertRange || s.invert)(range)
    : (s.invert || s.invertExtent)(range);
}

function geoMethod(methodName, globalMethod) {
  return function(projection, geojson, group) {
    if (projection) {
      // projection defined, use it
      const p = getScale(projection, (group || this).context);
      return p && p.path[methodName](geojson);
    } else {
      // projection undefined, use global method
      return globalMethod(geojson);
    }
  };
}

const geoArea = geoMethod('area', geoArea$1);
const geoBounds = geoMethod('bounds', geoBounds$1);
const geoCentroid = geoMethod('centroid', geoCentroid$1);

function inScope(item) {
  let group = this.context.group,
      value = false;

  if (group) while (item) {
    if (item === group) { value = true; break; }
    item = item.mark.group;
  }
  return value;
}

function intersect$2(b, opt, group) {
  if (!b) return [];

  const [u, v] = b,
        box = new Bounds().set(u[0], u[1], v[0], v[1]),
        scene = group || this.context.dataflow.scenegraph().root;

  return intersect(scene, box, filter$2(opt));
}

function filter$2(opt) {
  let p = null;

  if (opt) {
    const types = array(opt.marktype),
          names = array(opt.markname);
    p = _ => (!types.length || types.some(t => _.marktype === t))
          && (!names.length || names.some(s => _.name === s));
  }

  return p;
}

function log$3(df, method, args) {
  try {
    df[method].apply(df, ['EXPRESSION'].concat([].slice.call(args)));
  } catch (err) {
    df.warn(err);
  }
  return args[args.length-1];
}

function warn() {
  return log$3(this.context.dataflow, 'warn', arguments);
}

function info() {
  return log$3(this.context.dataflow, 'info', arguments);
}

function debug() {
  return log$3(this.context.dataflow, 'debug', arguments);
}

function merge$2() {
  var args = [].slice.call(arguments);
  args.unshift({});
  return extend.apply(null, args);
}

function equal(a, b) {
  return a === b || a !== a && b !== b ? true
    : isArray(a) ? (
        isArray(b) && a.length === b.length ? equalArray(a, b) : false
      )
    : isObject(a) && isObject(b) ? equalObject(a, b)
    : false;
}

function equalArray(a, b) {
  for (let i=0, n=a.length; i<n; ++i) {
    if (!equal(a[i], b[i])) return false;
  }
  return true;
}

function equalObject(a, b) {
  for (let key in a) {
    if (!equal(a[key], b[key])) return false;
  }
  return true;
}

function removePredicate(props) {
  return _ => equalObject(props, _);
}

function modify(name, insert, remove, toggle, modify, values) {
  let df = this.context.dataflow,
      data = this.context.data[name],
      input = data.input,
      changes = data.changes,
      stamp = df.stamp(),
      predicate, key;

  if (df._trigger === false || !(input.value.length || insert || toggle)) {
    // nothing to do!
    return 0;
  }

  if (!changes || changes.stamp < stamp) {
    data.changes = (changes = df.changeset());
    changes.stamp = stamp;
    df.runAfter(function() {
      data.modified = true;
      df.pulse(input, changes).run();
    }, true, 1);
  }

  if (remove) {
    predicate = remove === true ? truthy
      : (isArray(remove) || isTuple(remove)) ? remove
      : removePredicate(remove);
    changes.remove(predicate);
  }

  if (insert) {
    changes.insert(insert);
  }

  if (toggle) {
    predicate = removePredicate(toggle);
    if (input.value.some(predicate)) {
      changes.remove(predicate);
    } else {
      changes.insert(toggle);
    }
  }

  if (modify) {
    for (key in values) {
      changes.modify(modify, key, values[key]);
    }
  }

  return 1;
}

function pinchDistance(event) {
  const t = event.touches,
        dx = t[0].clientX - t[1].clientX,
        dy = t[0].clientY - t[1].clientY;
  return Math.sqrt(dx * dx + dy * dy);
}

function pinchAngle(event) {
  const t = event.touches;
  return Math.atan2(
    t[0].clientY - t[1].clientY,
    t[0].clientX - t[1].clientX
  );
}

function scaleGradient(scale, p0, p1, count, group) {
  scale = getScale(scale, (group || this).context);

  const gradient = Gradient(p0, p1);

  let stops = scale.domain(),
      min = stops[0],
      max = peek(stops),
      fraction = identity;

  if (!(max - min)) {
    // expand scale if domain has zero span, fix #1479
    scale = (scale.interpolator
      ? scale$2('sequential')().interpolator(scale.interpolator())
      : scale$2('linear')().interpolate(scale.interpolate()).range(scale.range())
    ).domain([min=0, max=1]);
  } else {
    fraction = scaleFraction(scale, min, max);
  }

  if (scale.ticks) {
    stops = scale.ticks(+count || 15);
    if (min !== stops[0]) stops.unshift(min);
    if (max !== peek(stops)) stops.push(max);
  }

  stops.forEach(_ => gradient.stop(fraction(_), scale(_)));

  return gradient;
}

function geoShape(projection, geojson, group) {
  const p = getScale(projection, (group || this).context);
  return function(context) {
    return p ? p.path.context(context)(geojson) : '';
  }
}

function pathShape(path) {
  let p = null;
  return function(context) {
    return context
      ? pathRender(context, (p = p || pathParse(path)))
      : path;
  };
}

const EMPTY = {};

function datum(d) { return d.data; }

function treeNodes(name, context) {
  const tree = data$1.call(context, name);
  return tree.root && tree.root.lookup || EMPTY;
}

function treePath(name, source, target) {
  const nodes = treeNodes(name, this),
        s = nodes[source],
        t = nodes[target];
  return s && t ? s.path(t).map(datum) : undefined;
}

function treeAncestors(name, node) {
  const n = treeNodes(name, this)[node];
  return n ? n.ancestors().map(datum) : undefined;
}

const _window = (typeof window !== 'undefined' && window) || null;

function screen() {
  return _window ? _window.screen : {};
}

function windowSize() {
  return _window
    ? [_window.innerWidth, _window.innerHeight]
    : [undefined, undefined];
}

function containerSize() {
  const view = this.context.dataflow,
        el = view.container && view.container();
  return el
    ? [el.clientWidth, el.clientHeight]
    : [undefined, undefined];
}

const DataPrefix$1   = ':';
const IndexPrefix$1  = '@';
const ScalePrefix  = '%';
const SignalPrefix = '$';

function dataVisitor(name, args, scope, params) {
  if (args[0].type !== Literal) {
    error('First argument to data functions must be a string literal.');
  }

  const data = args[0].value,
        dataName = DataPrefix$1 + data;

  if (!hasOwnProperty(dataName, params)) {
    try {
      params[dataName] = scope.getData(data).tuplesRef();
    } catch (err) {
      // if data set does not exist, there's nothing to track
    }
  }
}

function indataVisitor(name, args, scope, params) {
  if (args[0].type !== Literal) error('First argument to indata must be a string literal.');
  if (args[1].type !== Literal) error('Second argument to indata must be a string literal.');

  const data = args[0].value,
        field = args[1].value,
        indexName = IndexPrefix$1 + field;

  if (!hasOwnProperty(indexName, params)) {
    params[indexName] = scope.getData(data).indataRef(scope, field);
  }
}

function scaleVisitor(name, args, scope, params) {
  if (args[0].type === Literal) {
    // add scale dependency
    addScaleDependency(scope, params, args[0].value);
  }
  else if (args[0].type === Identifier$1) {
    // indirect scale lookup; add all scales as parameters
    for (name in scope.scales) {
      addScaleDependency(scope, params, name);
    }
  }
}

function addScaleDependency(scope, params, name) {
  const scaleName = ScalePrefix + name;
  if (!hasOwnProperty(params, scaleName)) {
    try {
      params[scaleName] = scope.scaleRef(name);
    } catch (err) {
      // TODO: error handling? warning?
    }
  }
}

// Expression function context object
const functionContext = {
  random: function() { return random(); }, // override default
  cumulativeNormal,
  cumulativeLogNormal,
  cumulativeUniform,
  densityNormal,
  densityLogNormal,
  densityUniform,
  quantileNormal,
  quantileLogNormal,
  quantileUniform,
  sampleNormal,
  sampleLogNormal,
  sampleUniform,
  isArray,
  isBoolean,
  isDate,
  isDefined: function(_) { return _ !== undefined; },
  isNumber,
  isObject,
  isRegExp,
  isString,
  isTuple,
  isValid: function(_) { return _ != null && _ === _; },
  toBoolean,
  toDate,
  toNumber,
  toString,
  flush,
  lerp,
  merge: merge$2,
  pad,
  peek,
  span,
  inrange,
  truncate,
  rgb,
  lab,
  hcl,
  hsl,
  luminance,
  contrast,
  sequence,
  format: format$1,
  utcFormat: utcFormat$1,
  utcParse,
  utcOffset,
  utcSequence,
  timeFormat: timeFormat$1,
  timeParse,
  timeOffset,
  timeSequence,
  timeUnitSpecifier,
  monthFormat,
  monthAbbrevFormat,
  dayFormat,
  dayAbbrevFormat,
  quarter,
  utcquarter,
  warn,
  info,
  debug,
  extent,
  inScope,
  intersect: intersect$2,
  clampRange,
  pinchDistance,
  pinchAngle,
  screen,
  containerSize,
  windowSize,
  bandspace,
  setdata,
  pathShape,
  panLinear,
  panLog,
  panPow,
  panSymlog,
  zoomLinear,
  zoomLog,
  zoomPow,
  zoomSymlog,
  encode: encode$1,
  modify
};

const eventFunctions = ['view', 'item', 'group', 'xy', 'x', 'y'], // event functions
      eventPrefix = 'event.vega.', // event function prefix
      thisPrefix = 'this.', // function context prefix
      astVisitors = {}; // AST visitors for dependency analysis

// Build expression function registry
function buildFunctions(codegen) {
  const fn = functions(codegen);
  eventFunctions.forEach(name => fn[name] = eventPrefix + name);
  for (let name in functionContext) { fn[name] = thisPrefix + name; }
  return fn;
}

// Register an expression function
function expressionFunction(name, fn, visitor) {
  if (arguments.length === 1) {
    return functionContext[name];
  }

  // register with the functionContext
  functionContext[name] = fn;

  // if there is an astVisitor register that, too
  if (visitor) astVisitors[name] = visitor;

  // if the code generator has already been initialized,
  // we need to also register the function with it
  if (codeGenerator) codeGenerator.functions[name] = thisPrefix + name;
  return this;
}

// register expression functions with ast visitors
expressionFunction('bandwidth', bandwidth, scaleVisitor);
expressionFunction('copy', copy$2, scaleVisitor);
expressionFunction('domain', domain, scaleVisitor);
expressionFunction('range', range$1, scaleVisitor);
expressionFunction('invert', invert, scaleVisitor);
expressionFunction('scale', scale$3, scaleVisitor);
expressionFunction('gradient', scaleGradient, scaleVisitor);
expressionFunction('geoArea', geoArea, scaleVisitor);
expressionFunction('geoBounds', geoBounds, scaleVisitor);
expressionFunction('geoCentroid', geoCentroid, scaleVisitor);
expressionFunction('geoShape', geoShape, scaleVisitor);
expressionFunction('indata', indata, indataVisitor);
expressionFunction('data', data$1, dataVisitor);
expressionFunction('treePath', treePath, dataVisitor);
expressionFunction('treeAncestors', treeAncestors, dataVisitor);

// register Vega-Lite selection functions
expressionFunction('vlSelectionTest', selectionTest, selectionVisitor);
expressionFunction('vlSelectionResolve', selectionResolve, selectionVisitor);

// Export code generator and parameters
const codegenParams = {
  blacklist:  ['_'],
  whitelist:  ['datum', 'event', 'item'],
  fieldvar:   'datum',
  globalvar:  function(id) { return '_[' + $(SignalPrefix + id) + ']'; },
  functions:  buildFunctions,
  constants:  constants,
  visitors:   astVisitors
};

var codeGenerator = codegen(codegenParams);

/**
 * Parse an expression given the argument signature and body code.
 */
function expression(args, code, ctx) {
  // wrap code in return statement if expression does not terminate
  if (code[code.length-1] !== ';') {
    code = 'return(' + code + ');';
  }
  var fn = Function.apply(null, args.concat(code));
  return ctx && ctx.functions ? fn.bind(ctx.functions) : fn;
}

/**
 * Parse an expression used to update an operator value.
 */
function operatorExpression(code, ctx) {
  return expression(['_'], code, ctx);
}

/**
 * Parse an expression provided as an operator parameter value.
 */
function parameterExpression(code, ctx) {
  return expression(['datum', '_'], code, ctx);
}

/**
 * Parse an expression applied to an event stream.
 */
function eventExpression(code, ctx) {
  return expression(['event'], code, ctx);
}

/**
 * Parse an expression used to handle an event-driven operator update.
 */
function handlerExpression(code, ctx) {
  return expression(['_', 'event'], code, ctx);
}

/**
 * Parse an expression that performs visual encoding.
 */
function encodeExpression(code, ctx) {
  return expression(['item', '_'], code, ctx);
}

/**
 * Parse a set of operator parameters.
 */
function parseParameters(spec, ctx, params) {
  params = params || {};
  var key, value;

  for (key in spec) {
    value = spec[key];

    params[key] = isArray(value)
      ? value.map(function(v) { return parseParameter(v, ctx, params); })
      : parseParameter(value, ctx, params);
  }
  return params;
}

/**
 * Parse a single parameter.
 */
function parseParameter(spec, ctx, params) {
  if (!spec || !isObject(spec)) return spec;

  for (var i=0, n=PARSERS.length, p; i<n; ++i) {
    p = PARSERS[i];
    if (hasOwnProperty(spec, p.key)) {
      return p.parse(spec, ctx, params);
    }
  }
  return spec;
}

/** Reference parsers. */
var PARSERS = [
  {key: '$ref',      parse: getOperator},
  {key: '$key',      parse: getKey},
  {key: '$expr',     parse: getExpression},
  {key: '$field',    parse: getField$1},
  {key: '$encode',   parse: getEncode},
  {key: '$compare',  parse: getCompare},
  {key: '$context',  parse: getContext},
  {key: '$subflow',  parse: getSubflow},
  {key: '$tupleid',  parse: getTupleId}
];

/**
 * Resolve an operator reference.
 */
function getOperator(_, ctx) {
  return ctx.get(_.$ref) || error('Operator not defined: ' + _.$ref);
}

/**
 * Resolve an expression reference.
 */
function getExpression(_, ctx, params) {
  if (_.$params) { // parse expression parameters
    parseParameters(_.$params, ctx, params);
  }
  var k = 'e:' + _.$expr + '_' + _.$name;
  return ctx.fn[k]
    || (ctx.fn[k] = accessor(parameterExpression(_.$expr, ctx), _.$fields, _.$name));
}

/**
 * Resolve a key accessor reference.
 */
function getKey(_, ctx) {
  var k = 'k:' + _.$key + '_' + (!!_.$flat);
  return ctx.fn[k] || (ctx.fn[k] = key(_.$key, _.$flat));
}

/**
 * Resolve a field accessor reference.
 */
function getField$1(_, ctx) {
  if (!_.$field) return null;
  var k = 'f:' + _.$field + '_' + _.$name;
  return ctx.fn[k] || (ctx.fn[k] = field(_.$field, _.$name));
}

/**
 * Resolve a comparator function reference.
 */
function getCompare(_, ctx) {
  // As of Vega 5.5.3, $tupleid sort is no longer used.
  // Keep here for now for backwards compatibility.
  var k = 'c:' + _.$compare + '_' + _.$order,
      c = array(_.$compare).map(function(_) {
        return (_ && _.$tupleid) ? tupleid : _;
      });
  return ctx.fn[k] || (ctx.fn[k] = compare(c, _.$order));
}

/**
 * Resolve an encode operator reference.
 */
function getEncode(_, ctx) {
  var spec = _.$encode,
      encode = {}, name, enc;

  for (name in spec) {
    enc = spec[name];
    encode[name] = accessor(encodeExpression(enc.$expr, ctx), enc.$fields);
    encode[name].output = enc.$output;
  }
  return encode;
}

/**
 * Resolve a context reference.
 */
function getContext(_, ctx) {
  return ctx;
}

/**
 * Resolve a recursive subflow specification.
 */
function getSubflow(_, ctx) {
  var spec = _.$subflow;
  return function(dataflow, key, parent) {
    var subctx = parse$4(spec, ctx.fork()),
        op = subctx.get(spec.operators[0].id),
        p = subctx.signals.parent;
    if (p) p.set(parent);
    return op;
  };
}

/**
 * Resolve a tuple id reference.
 */
function getTupleId() {
  return tupleid;
}

function canonicalType(type) {
  return (type + '').toLowerCase();
}
function isOperator(type) {
   return canonicalType(type) === 'operator';
}

function isCollect(type) {
  return canonicalType(type) === 'collect';
}

/**
 * Parse a dataflow operator.
 */
function parseOperator(spec, ctx) {
  if (isOperator(spec.type) || !spec.type) {
    ctx.operator(spec,
      spec.update ? operatorExpression(spec.update, ctx) : null);
  } else {
    ctx.transform(spec, spec.type);
  }
}

/**
 * Parse and assign operator parameters.
 */
function parseOperatorParameters(spec, ctx) {
  if (spec.params) {
    var op = ctx.get(spec.id);
    if (!op) error('Invalid operator id: ' + spec.id);
    ctx.dataflow.connect(op, op.parameters(
      parseParameters(spec.params, ctx),
      spec.react,
      spec.initonly
    ));
  }
}

/**
 * Parse an event stream specification.
 */
function parseStream(spec, ctx) {
  var filter = spec.filter != null ? eventExpression(spec.filter, ctx) : undefined,
      stream = spec.stream != null ? ctx.get(spec.stream) : undefined,
      args;

  if (spec.source) {
    stream = ctx.events(spec.source, spec.type, filter);
  }
  else if (spec.merge) {
    args = spec.merge.map(ctx.get.bind(ctx));
    stream = args[0].merge.apply(args[0], args.slice(1));
  }

  if (spec.between) {
    args = spec.between.map(ctx.get.bind(ctx));
    stream = stream.between(args[0], args[1]);
  }

  if (spec.filter) {
    stream = stream.filter(filter);
  }

  if (spec.throttle != null) {
    stream = stream.throttle(+spec.throttle);
  }

  if (spec.debounce != null) {
    stream = stream.debounce(+spec.debounce);
  }

  if (stream == null) {
    error('Invalid stream definition: ' + JSON.stringify(spec));
  }

  if (spec.consume) stream.consume(true);

  ctx.stream(spec, stream);
}

/**
 * Parse an event-driven operator update.
 */
function parseUpdate(spec, ctx) {
  var srcid = isObject(srcid = spec.source) ? srcid.$ref : srcid,
      source = ctx.get(srcid),
      target = null,
      update = spec.update,
      params = undefined;

  if (!source) error('Source not defined: ' + spec.source);

  if (spec.target && spec.target.$expr) {
    target = eventExpression(spec.target.$expr, ctx);
  } else {
    target = ctx.get(spec.target);
  }

  if (update && update.$expr) {
    if (update.$params) {
      params = parseParameters(update.$params, ctx);
    }
    update = handlerExpression(update.$expr, ctx);
  }

  ctx.update(spec, source, target, update, params);
}

/**
 * Parse a serialized dataflow specification.
 */
function parse$4(spec, ctx) {
  var operators = spec.operators || [];

  // parse background
  if (spec.background) {
    ctx.background = spec.background;
  }

  // parse event configuration
  if (spec.eventConfig) {
    ctx.eventConfig = spec.eventConfig;
  }

  // parse operators
  operators.forEach(function(entry) {
    parseOperator(entry, ctx);
  });

  // parse operator parameters
  operators.forEach(function(entry) {
    parseOperatorParameters(entry, ctx);
  });

  // parse streams
  (spec.streams || []).forEach(function(entry) {
    parseStream(entry, ctx);
  });

  // parse updates
  (spec.updates || []).forEach(function(entry) {
    parseUpdate(entry, ctx);
  });

  return ctx.resolve();
}

var SKIP$3 = {skip: true};

function getState(options) {
  var ctx = this,
      state = {};

  if (options.signals) {
    var signals = (state.signals = {});
    Object.keys(ctx.signals).forEach(function(key) {
      var op = ctx.signals[key];
      if (options.signals(key, op)) {
        signals[key] = op.value;
      }
    });
  }

  if (options.data) {
    var data = (state.data = {});
    Object.keys(ctx.data).forEach(function(key) {
      var dataset = ctx.data[key];
      if (options.data(key, dataset)) {
        data[key] = dataset.input.value;
      }
    });
  }

  if (ctx.subcontext && options.recurse !== false) {
    state.subcontext = ctx.subcontext.map(function(ctx) {
      return ctx.getState(options);
    });
  }

  return state;
}

function setState(state) {
  var ctx = this,
      df = ctx.dataflow,
      data = state.data,
      signals = state.signals;

  Object.keys(signals || {}).forEach(function(key) {
    df.update(ctx.signals[key], signals[key], SKIP$3);
  });

  Object.keys(data || {}).forEach(function(key) {
    df.pulse(
      ctx.data[key].input,
      df.changeset().remove(truthy).insert(data[key])
    );
  });

  (state.subcontext  || []).forEach(function(substate, i) {
    var subctx = ctx.subcontext[i];
    if (subctx) subctx.setState(substate);
  });
}

/**
 * Context objects store the current parse state.
 * Enables lookup of parsed operators, event streams, accessors, etc.
 * Provides a 'fork' method for creating child contexts for subflows.
 */
function context$2(df, transforms, functions) {
  return new Context(df, transforms, functions);
}

function Context(df, transforms, functions) {
  this.dataflow = df;
  this.transforms = transforms;
  this.events = df.events.bind(df);
  this.signals = {};
  this.scales = {};
  this.nodes = {};
  this.data = {};
  this.fn = {};
  if (functions) {
    this.functions = Object.create(functions);
    this.functions.context = this;
  }
}

function ContextFork(ctx) {
  this.dataflow = ctx.dataflow;
  this.transforms = ctx.transforms;
  this.functions = ctx.functions;
  this.events = ctx.events;
  this.signals = Object.create(ctx.signals);
  this.scales = Object.create(ctx.scales);
  this.nodes = Object.create(ctx.nodes);
  this.data = Object.create(ctx.data);
  this.fn = Object.create(ctx.fn);
  if (ctx.functions) {
    this.functions = Object.create(ctx.functions);
    this.functions.context = this;
  }
}

Context.prototype = ContextFork.prototype = {
  fork: function() {
    var ctx = new ContextFork(this);
    (this.subcontext || (this.subcontext = [])).push(ctx);
    return ctx;
  },
  get: function(id) {
    return this.nodes[id];
  },
  set: function(id, node) {
    return this.nodes[id] = node;
  },
  add: function(spec, op) {
    var ctx = this,
        df = ctx.dataflow,
        data;

    ctx.set(spec.id, op);

    if (isCollect(spec.type) && (data = spec.value)) {
      if (data.$ingest) {
        df.ingest(op, data.$ingest, data.$format);
      } else if (data.$request) {
        df.preload(op, data.$request, data.$format);
      } else {
        df.pulse(op, df.changeset().insert(data));
      }
    }

    if (spec.root) {
      ctx.root = op;
    }

    if (spec.parent) {
      var p = ctx.get(spec.parent.$ref);
      if (p) {
        df.connect(p, [op]);
        op.targets().add(p);
      } else {
        (ctx.unresolved = ctx.unresolved || []).push(function() {
          p = ctx.get(spec.parent.$ref);
          df.connect(p, [op]);
          op.targets().add(p);
        });
      }
    }

    if (spec.signal) {
      ctx.signals[spec.signal] = op;
    }

    if (spec.scale) {
      ctx.scales[spec.scale] = op;
    }

    if (spec.data) {
      for (var name in spec.data) {
        data = ctx.data[name] || (ctx.data[name] = {});
        spec.data[name].forEach(function(role) { data[role] = op; });
      }
    }
  },
  resolve: function() {
    (this.unresolved || []).forEach(function(fn) { fn(); });
    delete this.unresolved;
    return this;
  },
  operator: function(spec, update) {
    this.add(spec, this.dataflow.add(spec.value, update));
  },
  transform: function(spec, type) {
    this.add(spec, this.dataflow.add(this.transforms[canonicalType(type)]));
  },
  stream: function(spec, stream) {
    this.set(spec.id, stream);
  },
  update: function(spec, stream, target, update, params) {
    this.dataflow.on(stream, target, update, params, spec.options);
  },
  getState: getState,
  setState: setState
};

function runtime(view, spec, functions) {
  var fn = functions || functionContext;
  return parse$4(spec, context$2(view, transforms, fn));
}

function scale$4(name) {
  var scales = this._runtime.scales;
  if (!hasOwnProperty(scales, name)) {
    error('Unrecognized scale or projection: ' + name);
  }
  return scales[name].value;
}

var Width = 'width',
    Height = 'height',
    Padding$1 = 'padding',
    Skip = {skip: true};

function viewWidth(view, width) {
  var a = view.autosize(),
      p = view.padding();
  return width - (a && a.contains === Padding$1 ? p.left + p.right : 0);
}

function viewHeight(view, height) {
  var a = view.autosize(),
      p = view.padding();
  return height - (a && a.contains === Padding$1 ? p.top + p.bottom : 0);
}

function initializeResize(view) {
  var s = view._signals,
      w = s[Width],
      h = s[Height],
      p = s[Padding$1];

  function resetSize() {
    view._autosize = view._resize = 1;
  }

  // respond to width signal
  view._resizeWidth = view.add(null,
    function(_) {
      view._width = _.size;
      view._viewWidth = viewWidth(view, _.size);
      resetSize();
    },
    {size: w}
  );

  // respond to height signal
  view._resizeHeight = view.add(null,
    function(_) {
      view._height = _.size;
      view._viewHeight = viewHeight(view, _.size);
      resetSize();
    },
    {size: h}
  );

  // respond to padding signal
  var resizePadding = view.add(null, resetSize, {pad: p});

  // set rank to run immediately after source signal
  view._resizeWidth.rank = w.rank + 1;
  view._resizeHeight.rank = h.rank + 1;
  resizePadding.rank = p.rank + 1;
}

function resizeView(viewWidth, viewHeight, width, height, origin, auto) {
  this.runAfter(function(view) {
    var rerun = 0;

    // reset autosize flag
    view._autosize = 0;

    // width value changed: update signal, skip resize op
    if (view.width() !== width) {
      rerun = 1;
      view.signal(Width, width, Skip); // set width, skip update calc
      view._resizeWidth.skip(true); // skip width resize handler
    }

    // height value changed: update signal, skip resize op
    if (view.height() !== height) {
      rerun = 1;
      view.signal(Height, height, Skip); // set height, skip update calc
      view._resizeHeight.skip(true); // skip height resize handler
    }

    // view width changed: update view property, set resize flag
    if (view._viewWidth !== viewWidth) {
      view._resize = 1;
      view._viewWidth = viewWidth;
    }

    // view height changed: update view property, set resize flag
    if (view._viewHeight !== viewHeight) {
      view._resize = 1;
      view._viewHeight = viewHeight;
    }

    // origin changed: update view property, set resize flag
    if (view._origin[0] !== origin[0] || view._origin[1] !== origin[1]) {
      view._resize = 1;
      view._origin = origin;
    }

    // run dataflow on width/height signal change
    if (rerun) view.run('enter');
    if (auto) view.runAfter(v => v.resize());
  }, false, 1);
}

/**
 * Get the current view state, consisting of signal values and/or data sets.
 * @param {object} [options] - Options flags indicating which state to export.
 *   If unspecified, all signals and data sets will be exported.
 * @param {function(string, Operator):boolean} [options.signals] - Optional
 *   predicate function for testing if a signal should be included in the
 *   exported state. If unspecified, all signals will be included, except for
 *   those named 'parent' or those which refer to a Transform value.
 * @param {function(string, object):boolean} [options.data] - Optional
 *   predicate function for testing if a data set's input should be included
 *   in the exported state. If unspecified, all data sets that have been
 *   explicitly modified will be included.
 * @param {boolean} [options.recurse=true] - Flag indicating if the exported
 *   state should recursively include state from group mark sub-contexts.
 * @return {object} - An object containing the exported state values.
 */
function getState$1(options) {
  return this._runtime.getState(options || {
    data:    dataTest,
    signals: signalTest,
    recurse: true
  });
}

function dataTest(name, data) {
  return data.modified
      && isArray(data.input.value)
      && name.indexOf('_:vega:_');
}

function signalTest(name, op) {
  return !(name === 'parent' || op instanceof transforms.proxy);
}

/**
 * Sets the current view state and updates the view by invoking run.
 * @param {object} state - A state object containing signal and/or
 *   data set values, following the format used by the getState method.
 * @return {View} - This view instance.
 */
function setState$1(state) {
  this.runAsync(null,
    v => { v._trigger = false; v._runtime.setState(state); },
    v => { v._trigger = true; }
  );
  return this;
}

function timer(callback, delay) {
  function tick(elapsed) {
    callback({timestamp: Date.now(), elapsed: elapsed});
  }
  this._timers.push(interval(tick, delay));
}

function defaultTooltip$1(handler, event, item, value) {
  var el = handler.element();
  if (el) el.setAttribute('title', formatTooltip(value));
}

function formatTooltip(value) {
  return value == null ? ''
    : isArray(value) ? formatArray(value)
    : isObject(value) && !isDate(value) ? formatObject(value)
    : value + '';
}

function formatObject(obj) {
  return Object.keys(obj).map(function(key) {
    var v = obj[key];
    return key + ': ' + (isArray(v) ? formatArray(v) : formatValue$1(v));
  }).join('\n');
}

function formatArray(value) {
  return '[' + value.map(formatValue$1).join(', ') + ']';
}

function formatValue$1(value) {
  return isArray(value) ? '[\u2026]'
    : isObject(value) && !isDate(value) ? '{\u2026}'
    : value;
}

/**
 * Create a new View instance from a Vega dataflow runtime specification.
 * The generated View will not immediately be ready for display. Callers
 * should also invoke the initialize method (e.g., to set the parent
 * DOM element in browser-based deployment) and then invoke the run
 * method to evaluate the dataflow graph. Rendering will automatically
 * be peformed upon dataflow runs.
 * @constructor
 * @param {object} spec - The Vega dataflow runtime specification.
 */
function View(spec, options) {
  var view = this;
  options = options || {};

  Dataflow.call(view);
  if (options.loader) view.loader(options.loader);
  if (options.logger) view.logger(options.logger);
  if (options.logLevel != null) view.logLevel(options.logLevel);

  view._el = null;
  view._elBind = null;
  view._renderType = options.renderer || RenderType.Canvas;
  view._scenegraph = new Scenegraph();
  var root = view._scenegraph.root;

  // initialize renderer, handler and event management
  view._renderer = null;
  view._tooltip = options.tooltip || defaultTooltip$1,
  view._redraw = true;
  view._handler = new CanvasHandler().scene(root);
  view._preventDefault = false;
  view._timers = [];
  view._eventListeners = [];
  view._resizeListeners = [];

  // initialize event configuration
  view._eventConfig = initializeEventConfig(spec.eventConfig);

  // initialize dataflow graph
  var ctx = runtime(view, spec, options.functions);
  view._runtime = ctx;
  view._signals = ctx.signals;
  view._bind = (spec.bindings || []).map(function(_) {
    return {
      state: null,
      param: extend({}, _)
    };
  });

  // initialize scenegraph
  if (ctx.root) ctx.root.set(root);
  root.source = ctx.data.root.input;
  view.pulse(
    ctx.data.root.input,
    view.changeset().insert(root.items)
  );

  // initialize background color
  view._background = options.background || ctx.background || null;

  // initialize view size
  view._width = view.width();
  view._height = view.height();
  view._viewWidth = viewWidth(view, view._width);
  view._viewHeight = viewHeight(view, view._height);
  view._origin = [0, 0];
  view._resize = 0;
  view._autosize = 1;
  initializeResize(view);

  // initialize cursor
  cursor(view);

  // initialize hover proessing, if requested
  if (options.hover) view.hover();

  // initialize DOM container(s) and renderer
  if (options.container) view.initialize(options.container, options.bind);
}

var prototype$1s = inherits(View, Dataflow);

// -- DATAFLOW / RENDERING ----

prototype$1s.evaluate = async function(encode, prerun, postrun) {
  // evaluate dataflow and prerun
  await Dataflow.prototype.evaluate.call(this, encode, prerun);

  // render as needed
  if (this._redraw || this._resize) {
    try {
      if (this._renderer) {
        if (this._resize) {
          this._resize = 0;
          resizeRenderer(this);
        }
        await this._renderer.renderAsync(this._scenegraph.root);
      }
      this._redraw = false;
    } catch (e) {
      this.error(e);
    }
  }

  // evaluate postrun
  if (postrun) asyncCallback(this, postrun);

  return this;
};

prototype$1s.dirty = function(item) {
  this._redraw = true;
  this._renderer && this._renderer.dirty(item);
};

// -- GET / SET ----

prototype$1s.container = function() {
  return this._el;
};

prototype$1s.scenegraph = function() {
  return this._scenegraph;
};

prototype$1s.origin = function() {
  return this._origin.slice();
};

function lookupSignal(view, name) {
  return hasOwnProperty(view._signals, name)
    ? view._signals[name]
    : error('Unrecognized signal name: ' + $(name));
}

prototype$1s.signal = function(name, value, options) {
  var op = lookupSignal(this, name);
  return arguments.length === 1
    ? op.value
    : this.update(op, value, options);
};

prototype$1s.background = function(_) {
  if (arguments.length) {
    this._background = _;
    this._resize = 1;
    return this;
  } else {
    return this._background;
  }
};

prototype$1s.width = function(_) {
  return arguments.length ? this.signal('width', _) : this.signal('width');
};

prototype$1s.height = function(_) {
  return arguments.length ? this.signal('height', _) : this.signal('height');
};

prototype$1s.padding = function(_) {
  return arguments.length ? this.signal('padding', _) : this.signal('padding');
};

prototype$1s.autosize = function(_) {
  return arguments.length ? this.signal('autosize', _) : this.signal('autosize');
};

prototype$1s.renderer = function(type) {
  if (!arguments.length) return this._renderType;
  if (!renderModule(type)) error('Unrecognized renderer type: ' + type);
  if (type !== this._renderType) {
    this._renderType = type;
    this._resetRenderer();
  }
  return this;
};

prototype$1s.tooltip = function(handler) {
  if (!arguments.length) return this._tooltip;
  if (handler !== this._tooltip) {
    this._tooltip = handler;
    this._resetRenderer();
  }
  return this;
};

prototype$1s.loader = function(loader) {
  if (!arguments.length) return this._loader;
  if (loader !== this._loader) {
    Dataflow.prototype.loader.call(this, loader);
    this._resetRenderer();
  }
  return this;
};

prototype$1s.resize = function() {
  // set flag to perform autosize
  this._autosize = 1;
  // touch autosize signal to ensure top-level ViewLayout runs
  return this.touch(lookupSignal(this, 'autosize'));
};

prototype$1s._resetRenderer = function() {
  if (this._renderer) {
    this._renderer = null;
    this.initialize(this._el, this._elBind);
  }
};

// -- SIZING ----
prototype$1s._resizeView = resizeView;

// -- EVENT HANDLING ----

prototype$1s.addEventListener = function(type, handler, options) {
  var callback = handler;
  if (!(options && options.trap === false)) {
    // wrap callback in error handler
    callback = trap(this, handler);
    callback.raw = handler;
  }
  this._handler.on(type, callback);
  return this;
};

prototype$1s.removeEventListener = function(type, handler) {
  var handlers = this._handler.handlers(type),
      i = handlers.length, h, t;

  // search registered handlers, remove if match found
  while (--i >= 0) {
    t = handlers[i].type;
    h = handlers[i].handler;
    if (type === t && (handler === h || handler === h.raw)) {
      this._handler.off(t, h);
      break;
    }
  }
  return this;
};

prototype$1s.addResizeListener = function(handler) {
  var l = this._resizeListeners;
  if (l.indexOf(handler) < 0) {
    // add handler if it isn't already registered
    // note: error trapping handled elsewhere, so
    // no need to wrap handlers here
    l.push(handler);
  }
  return this;
};

prototype$1s.removeResizeListener = function(handler) {
  var l = this._resizeListeners,
      i = l.indexOf(handler);
  if (i >= 0) {
    l.splice(i, 1);
  }
  return this;
};

function findOperatorHandler(op, handler) {
  var t = op._targets || [],
      h = t.filter(function(op) {
            var u = op._update;
            return u && u.handler === handler;
          });
  return h.length ? h[0] : null;
}

function addOperatorListener(view, name, op, handler) {
  var h = findOperatorHandler(op, handler);
  if (!h) {
    h = trap(this, function() { handler(name, op.value); });
    h.handler = handler;
    view.on(op, null, h);
  }
  return view;
}

function removeOperatorListener(view, op, handler) {
  var h = findOperatorHandler(op, handler);
  if (h) op._targets.remove(h);
  return view;
}

prototype$1s.addSignalListener = function(name, handler) {
  return addOperatorListener(this, name, lookupSignal(this, name), handler);
};

prototype$1s.removeSignalListener = function(name, handler) {
  return removeOperatorListener(this, lookupSignal(this, name), handler);
};

prototype$1s.addDataListener = function(name, handler) {
  return addOperatorListener(this, name, dataref(this, name).values, handler);
};

prototype$1s.removeDataListener = function(name, handler) {
  return removeOperatorListener(this, dataref(this, name).values, handler);
};

prototype$1s.preventDefault = function(_) {
  if (arguments.length) {
    this._preventDefault = _;
    return this;
  } else {
    return this._preventDefault;
  }
};

prototype$1s.timer = timer;
prototype$1s.events = events$1;
prototype$1s.finalize = finalize;
prototype$1s.hover = hover;

// -- DATA ----
prototype$1s.data = data;
prototype$1s.change = change;
prototype$1s.insert = insert;
prototype$1s.remove = remove;

// -- SCALES --
prototype$1s.scale = scale$4;

// -- INITIALIZATION ----
prototype$1s.initialize = initialize$1;

// -- HEADLESS RENDERING ----
prototype$1s.toImageURL = renderToImageURL;
prototype$1s.toCanvas = renderToCanvas;
prototype$1s.toSVG = renderToSVG;

// -- SAVE / RESTORE STATE ----
prototype$1s.getState = getState$1;
prototype$1s.setState = setState$1;

function parseAutosize(spec, config) {
  spec = spec || config.autosize;
  return isObject(spec)
    ? spec
    : {type: spec || 'pad'};
}

function parsePadding(spec, config) {
  spec = spec || config.padding;
  return isObject(spec)
    ? {
        top:    number$5(spec.top),
        bottom: number$5(spec.bottom),
        left:   number$5(spec.left),
        right:  number$5(spec.right)
      }
    : paddingObject(number$5(spec));
}

function number$5(_) {
  return +_ || 0;
}

function paddingObject(_) {
  return {top: _, bottom: _, left: _, right: _};
}

var OUTER = 'outer',
    OUTER_INVALID = ['value', 'update', 'init', 'react', 'bind'];

function outerError(prefix, name) {
  error(prefix + ' for "outer" push: ' + $(name));
}

function parseSignal(signal, scope) {
  var name = signal.name;

  if (signal.push === OUTER) {
    // signal must already be defined, raise error if not
    if (!scope.signals[name]) outerError('No prior signal definition', name);
    // signal push must not use properties reserved for standard definition
    OUTER_INVALID.forEach(function(prop) {
      if (signal[prop] !== undefined) outerError('Invalid property ', prop);
    });
  } else {
    // define a new signal in the current scope
    var op = scope.addSignal(name, signal.value);
    if (signal.react === false) op.react = false;
    if (signal.bind) scope.addBinding(name, signal.bind);
  }
}

function parseExpression$1(expr, scope, preamble) {
  var params = {}, ast, gen;

  // parse the expression to an abstract syntax tree (ast)
  try {
    expr = isString(expr) ? expr : ($(expr) + '');
    ast = parse$3(expr);
  } catch (err) {
    error('Expression parse error: ' + expr);
  }

  // analyze ast function calls for dependencies
  ast.visit(function visitor(node) {
    if (node.type !== CallExpression) return;
    var name = node.callee.name,
        visit = codegenParams.visitors[name];
    if (visit) visit(name, node.arguments, scope, params);
  });

  // perform code generation
  gen = codeGenerator(ast);

  // collect signal dependencies
  gen.globals.forEach(function(name) {
    var signalName = SignalPrefix + name;
    if (!hasOwnProperty(params, signalName) && scope.getSignal(name)) {
      params[signalName] = scope.signalRef(name);
    }
  });

  // return generated expression code and dependencies
  return {
    $expr:   preamble ? preamble + 'return(' + gen.code + ');' : gen.code,
    $fields: gen.fields,
    $params: params
  };
}

function Entry(type, value, params, parent) {
  this.id = -1;
  this.type = type;
  this.value = value;
  this.params = params;
  if (parent) this.parent = parent;
}

function entry(type, value, params, parent) {
  return new Entry(type, value, params, parent);
}

function operator(value, params) {
  return entry('operator', value, params);
}

// -----

function ref(op) {
  var ref = {$ref: op.id};
  // if operator not yet registered, cache ref to resolve later
  if (op.id < 0) (op.refs = op.refs || []).push(ref);
  return ref;
}

function fieldRef(field, name) {
  return name ? {$field: field, $name: name} : {$field: field};
}

var keyFieldRef = fieldRef('key');

function compareRef(fields, orders) {
  return {$compare: fields, $order: orders};
}

function keyRef(fields, flat) {
  var ref = {$key: fields};
  if (flat) ref.$flat = true;
  return ref;
}

// -----

var Ascending  = 'ascending';

var Descending = 'descending';

function sortKey(sort) {
  return !isObject(sort) ? ''
    : (sort.order === Descending ? '-' : '+')
      + aggrField(sort.op, sort.field);
}

function aggrField(op, field) {
  return (op && op.signal ? '$' + op.signal : op || '')
    + (op && field ? '_' : '')
    + (field && field.signal ? '$' + field.signal : field || '');
}

// -----

var Scope = 'scope';

var View$1 = 'view';

function isSignal(_) {
  return _ && _.signal;
}

function isExpr(_) {
  return _ && _.expr;
}

function hasSignal(_) {
  if (isSignal(_)) return true;
  if (isObject(_)) for (var key in _) {
    if (hasSignal(_[key])) return true;
  }
  return false;
}

function value$1(specValue, defaultValue) {
  return specValue != null ? specValue : defaultValue;
}

function deref(v) {
  return v && v.signal || v;
}

var Timer = 'timer';

function parseStream$1(stream, scope) {
  var method = stream.merge ? mergeStream
    : stream.stream ? nestedStream
    : stream.type ? eventStream
    : error('Invalid stream specification: ' + $(stream));

  return method(stream, scope);
}

function eventSource(source) {
   return source === Scope ? View$1 : (source || View$1);
}

function mergeStream(stream, scope) {
  var list = stream.merge.map(s => parseStream$1(s, scope)),
      entry = streamParameters({merge: list}, stream, scope);
  return scope.addStream(entry).id;
}

function nestedStream(stream, scope) {
  var id = parseStream$1(stream.stream, scope),
      entry = streamParameters({stream: id}, stream, scope);
  return scope.addStream(entry).id;
}

function eventStream(stream, scope) {
  var id, entry;

  if (stream.type === Timer) {
    id = scope.event(Timer, stream.throttle);
    stream = {between: stream.between, filter: stream.filter};
  } else {
    id = scope.event(eventSource(stream.source), stream.type);
  }

  entry = streamParameters({stream: id}, stream, scope);
  return Object.keys(entry).length === 1
    ? id
    : scope.addStream(entry).id;
}

function streamParameters(entry, stream, scope) {
  var param = stream.between;

  if (param) {
    if (param.length !== 2) {
      error('Stream "between" parameter must have 2 entries: ' + $(stream));
    }
    entry.between = [
      parseStream$1(param[0], scope),
      parseStream$1(param[1], scope)
    ];
  }

  param = stream.filter ? [].concat(stream.filter) : [];
  if (stream.marktype || stream.markname || stream.markrole) {
    // add filter for mark type, name and/or role
    param.push(filterMark(stream.marktype, stream.markname, stream.markrole));
  }
  if (stream.source === Scope) {
    // add filter to limit events from sub-scope only
    param.push('inScope(event.item)');
  }
  if (param.length) {
    entry.filter = parseExpression$1('(' + param.join(')&&(') + ')').$expr;
  }

  if ((param = stream.throttle) != null) {
    entry.throttle = +param;
  }

  if ((param = stream.debounce) != null) {
    entry.debounce = +param;
  }

  if (stream.consume) {
    entry.consume = true;
  }

  return entry;
}

function filterMark(type, name, role) {
  var item = 'event.item';
  return item
    + (type && type !== '*' ? '&&' + item + '.mark.marktype===\'' + type + '\'' : '')
    + (role ? '&&' + item + '.mark.role===\'' + role + '\'' : '')
    + (name ? '&&' + item + '.mark.name===\'' + name + '\'' : '');
}

/**
 * Parse an event selector string.
 * Returns an array of event stream definitions.
 */
function selector(selector, source, marks) {
  DEFAULT_SOURCE = source || VIEW$1;
  MARKS = marks || DEFAULT_MARKS;
  return parseMerge(selector.trim()).map(parseSelector);
}

var VIEW$1    = 'view',
    LBRACK  = '[',
    RBRACK  = ']',
    LBRACE  = '{',
    RBRACE  = '}',
    COLON   = ':',
    COMMA   = ',',
    NAME    = '@',
    GT      = '>',
    ILLEGAL$1 = /[[\]{}]/,
    DEFAULT_SOURCE,
    MARKS,
    DEFAULT_MARKS = {
      '*': 1,
      arc: 1,
      area: 1,
      group: 1,
      image: 1,
      line: 1,
      path: 1,
      rect: 1,
      rule: 1,
      shape: 1,
      symbol: 1,
      text: 1,
      trail: 1
    };

function isMarkType(type) {
  return MARKS[type];
}

function find$1(s, i, endChar, pushChar, popChar) {
  var count = 0,
      n = s.length,
      c;
  for (; i<n; ++i) {
    c = s[i];
    if (!count && c === endChar) return i;
    else if (popChar && popChar.indexOf(c) >= 0) --count;
    else if (pushChar && pushChar.indexOf(c) >= 0) ++count;
  }
  return i;
}

function parseMerge(s) {
  var output = [],
      start = 0,
      n = s.length,
      i = 0;

  while (i < n) {
    i = find$1(s, i, COMMA, LBRACK + LBRACE, RBRACK + RBRACE);
    output.push(s.substring(start, i).trim());
    start = ++i;
  }

  if (output.length === 0) {
    throw 'Empty event selector: ' + s;
  }
  return output;
}

function parseSelector(s) {
  return s[0] === '['
    ? parseBetween(s)
    : parseStream$2(s);
}

function parseBetween(s) {
  var n = s.length,
      i = 1,
      b, stream;

  i = find$1(s, i, RBRACK, LBRACK, RBRACK);
  if (i === n) {
    throw 'Empty between selector: ' + s;
  }

  b = parseMerge(s.substring(1, i));
  if (b.length !== 2) {
    throw 'Between selector must have two elements: ' + s;
  }

  s = s.slice(i + 1).trim();
  if (s[0] !== GT) {
    throw 'Expected \'>\' after between selector: ' + s;
  }

  b = b.map(parseSelector);

  stream = parseSelector(s.slice(1).trim());
  if (stream.between) {
    return {
      between: b,
      stream: stream
    };
  } else {
    stream.between = b;
  }

  return stream;
}

function parseStream$2(s) {
  var stream = {source: DEFAULT_SOURCE},
      source = [],
      throttle = [0, 0],
      markname = 0,
      start = 0,
      n = s.length,
      i = 0, j,
      filter;

  // extract throttle from end
  if (s[n-1] === RBRACE) {
    i = s.lastIndexOf(LBRACE);
    if (i >= 0) {
      try {
        throttle = parseThrottle(s.substring(i+1, n-1));
      } catch (e) {
        throw 'Invalid throttle specification: ' + s;
      }
      s = s.slice(0, i).trim();
      n = s.length;
    } else throw 'Unmatched right brace: ' + s;
    i = 0;
  }

  if (!n) throw s;

  // set name flag based on first char
  if (s[0] === NAME) markname = ++i;

  // extract first part of multi-part stream selector
  j = find$1(s, i, COLON);
  if (j < n) {
    source.push(s.substring(start, j).trim());
    start = i = ++j;
  }

  // extract remaining part of stream selector
  i = find$1(s, i, LBRACK);
  if (i === n) {
    source.push(s.substring(start, n).trim());
  } else {
    source.push(s.substring(start, i).trim());
    filter = [];
    start = ++i;
    if (start === n) throw 'Unmatched left bracket: ' + s;
  }

  // extract filters
  while (i < n) {
    i = find$1(s, i, RBRACK);
    if (i === n) throw 'Unmatched left bracket: ' + s;
    filter.push(s.substring(start, i).trim());
    if (i < n-1 && s[++i] !== LBRACK) throw 'Expected left bracket: ' + s;
    start = ++i;
  }

  // marshall event stream specification
  if (!(n = source.length) || ILLEGAL$1.test(source[n-1])) {
    throw 'Invalid event selector: ' + s;
  }

  if (n > 1) {
    stream.type = source[1];
    if (markname) {
      stream.markname = source[0].slice(1);
    } else if (isMarkType(source[0])) {
      stream.marktype = source[0];
    } else {
      stream.source = source[0];
    }
  } else {
    stream.type = source[0];
  }
  if (stream.type.slice(-1) === '!') {
    stream.consume = true;
    stream.type = stream.type.slice(0, -1);
  }
  if (filter != null) stream.filter = filter;
  if (throttle[0]) stream.throttle = throttle[0];
  if (throttle[1]) stream.debounce = throttle[1];

  return stream;
}

function parseThrottle(s) {
  var a = s.split(COMMA);
  if (!s.length || a.length > 2) throw s;
  return a.map(function(_) {
    var x = +_;
    if (x !== x) throw s;
    return x;
  });
}

var preamble = 'var datum=event.item&&event.item.datum;';

function parseUpdate$1(spec, scope, target) {
  var events = spec.events,
      update = spec.update,
      encode = spec.encode,
      sources = [],
      entry = {target: target};

  if (!events) {
    error('Signal update missing events specification.');
  }

  // interpret as an event selector string
  if (isString(events)) {
    events = selector(events, scope.isSubscope() ? Scope : View$1);
  }

  // separate event streams from signal updates
  events = array(events)
    .filter(s => s.signal || s.scale ? (sources.push(s), 0) : 1);

  // merge internal operator listeners
  if (sources.length > 1) {
    sources = [mergeSources(sources)];
  }

  // merge event streams, include as source
  if (events.length) {
    sources.push(events.length > 1 ? {merge: events} : events[0]);
  }

  if (encode != null) {
    if (update) error('Signal encode and update are mutually exclusive.');
    update = 'encode(item(),' + $(encode) + ')';
  }

  // resolve update value
  entry.update = isString(update) ? parseExpression$1(update, scope, preamble)
    : update.expr != null ? parseExpression$1(update.expr, scope, preamble)
    : update.value != null ? update.value
    : update.signal != null ? {
        $expr:   '_.value',
        $params: {value: scope.signalRef(update.signal)}
      }
    : error('Invalid signal update specification.');

  if (spec.force) {
    entry.options = {force: true};
  }

  sources.forEach(function(source) {
    scope.addUpdate(extend(streamSource(source, scope), entry));
  });
}

function streamSource(stream, scope) {
  return {
    source: stream.signal ? scope.signalRef(stream.signal)
          : stream.scale ? scope.scaleRef(stream.scale)
          : parseStream$1(stream, scope)
  };
}

function mergeSources(sources) {
  return {
    signal: '['
      + sources.map(s => s.scale ? 'scale("' + s.scale + '")' : s.signal)
      + ']'
  };
}

function parseSignalUpdates(signal, scope) {
  var op = scope.getSignal(signal.name),
      expr = signal.update;

  if (signal.init) {
    if (expr) {
      error('Signals can not include both init and update expressions.');
    } else {
      expr = signal.init;
      op.initonly = true;
    }
  }

  if (expr) {
    expr = parseExpression$1(expr, scope);
    op.update = expr.$expr;
    op.params = expr.$params;
  }

  if (signal.on) {
    signal.on.forEach(function(_) {
      parseUpdate$1(_, scope, op.id);
    });
  }
}

function transform$2(name) {
  return function(params, value, parent) {
    return entry(name, value, params || undefined, parent);
  };
}

var Aggregate$1 = transform$2('aggregate');
var AxisTicks$1 = transform$2('axisticks');
var Bound$1 = transform$2('bound');
var Collect$1 = transform$2('collect');
var Compare$1 = transform$2('compare');
var DataJoin$1 = transform$2('datajoin');
var Encode$1 = transform$2('encode');
var Expression$1 = transform$2('expression');
var Facet$1 = transform$2('facet');
var Field$1 = transform$2('field');
var Key$1 = transform$2('key');
var LegendEntries$1 = transform$2('legendentries');
var Load$1 = transform$2('load');
var Mark$1 = transform$2('mark');
var MultiExtent$1 = transform$2('multiextent');
var MultiValues$1 = transform$2('multivalues');
var Overlap$1 = transform$2('overlap');
var Params$2 = transform$2('params');
var PreFacet$1 = transform$2('prefacet');
var Projection$1 = transform$2('projection');
var Proxy$1 = transform$2('proxy');
var Relay$1 = transform$2('relay');
var Render$1 = transform$2('render');
var Scale$1 = transform$2('scale');
var Sieve$1 = transform$2('sieve');
var SortItems$1 = transform$2('sortitems');
var ViewLayout$1 = transform$2('viewlayout');
var Values$1 = transform$2('values');

var FIELD_REF_ID = 0;

var MULTIDOMAIN_SORT_OPS  = {min: 'min', max: 'max', count: 'sum'};

function initScale(spec, scope) {
  var type = spec.type || 'linear';

  if (!isValidScaleType(type)) {
    error('Unrecognized scale type: ' + $(type));
  }

  scope.addScale(spec.name, {
    type:   type,
    domain: undefined
  });
}

function parseScale(spec, scope) {
  var params = scope.getScale(spec.name).params,
      key;

  params.domain = parseScaleDomain(spec.domain, spec, scope);

  if (spec.range != null) {
    params.range = parseScaleRange(spec, scope, params);
  }

  if (spec.interpolate != null) {
    parseScaleInterpolate(spec.interpolate, params);
  }

  if (spec.nice != null) {
    params.nice = parseScaleNice(spec.nice);
  }

  if (spec.bins != null) {
    params.bins = parseScaleBins(spec.bins, scope);
  }

  for (key in spec) {
    if (hasOwnProperty(params, key) || key === 'name') continue;
    params[key] = parseLiteral(spec[key], scope);
  }
}

function parseLiteral(v, scope) {
  return !isObject(v) ? v
    : v.signal ? scope.signalRef(v.signal)
    : error('Unsupported object: ' + $(v));
}

function parseArray(v, scope) {
  return v.signal
    ? scope.signalRef(v.signal)
    : v.map(v => parseLiteral(v, scope));
}

function dataLookupError(name) {
  error('Can not find data set: ' + $(name));
}

// -- SCALE DOMAIN ----

function parseScaleDomain(domain, spec, scope) {
  if (!domain) {
    if (spec.domainMin != null || spec.domainMax != null) {
      error('No scale domain defined for domainMin/domainMax to override.');
    }
    return; // default domain
  }

  return domain.signal ? scope.signalRef(domain.signal)
    : (isArray(domain) ? explicitDomain
    : domain.fields ? multipleDomain
    : singularDomain)(domain, spec, scope);
}

function explicitDomain(domain, spec, scope) {
  return domain.map(function(v) {
    return parseLiteral(v, scope);
  });
}

function singularDomain(domain, spec, scope) {
  var data = scope.getData(domain.data);
  if (!data) dataLookupError(domain.data);

  return isDiscrete(spec.type)
      ? data.valuesRef(scope, domain.field, parseSort(domain.sort, false))
      : isQuantile(spec.type) ? data.domainRef(scope, domain.field)
      : data.extentRef(scope, domain.field);
}

function multipleDomain(domain, spec, scope) {
  var data = domain.data,
      fields = domain.fields.reduce(function(dom, d) {
        d = isString(d) ? {data: data, field: d}
          : (isArray(d) || d.signal) ? fieldRef$1(d, scope)
          : d;
        dom.push(d);
        return dom;
      }, []);

  return (isDiscrete(spec.type) ? ordinalMultipleDomain
    : isQuantile(spec.type) ? quantileMultipleDomain
    : numericMultipleDomain)(domain, scope, fields);
}

function fieldRef$1(data, scope) {
  var name = '_:vega:_' + (FIELD_REF_ID++),
      coll = Collect$1({});

  if (isArray(data)) {
    coll.value = {$ingest: data};
  } else if (data.signal) {
    var code = 'setdata(' + $(name) + ',' + data.signal + ')';
    coll.params.input = scope.signalRef(code);
  }
  scope.addDataPipeline(name, [coll, Sieve$1({})]);
  return {data: name, field: 'data'};
}

function ordinalMultipleDomain(domain, scope, fields) {
  var sort = parseSort(domain.sort, true),
      counts, p, a, c, v;

  // get value counts for each domain field
  counts = fields.map(function(f) {
    var data = scope.getData(f.data);
    if (!data) dataLookupError(f.data);
    return data.countsRef(scope, f.field, sort);
  });

  // aggregate the results from each domain field
  p = {groupby: keyFieldRef, pulse: counts};
  if (sort) {
    a = sort.op || 'count';
    v = sort.field ? aggrField(a, sort.field) : 'count';
    p.ops = [MULTIDOMAIN_SORT_OPS[a]];
    p.fields = [scope.fieldRef(v)];
    p.as = [v];
  }
  a = scope.add(Aggregate$1(p));

  // collect aggregate output
  c = scope.add(Collect$1({pulse: ref(a)}));

  // extract values for combined domain
  v = scope.add(Values$1({
    field: keyFieldRef,
    sort:  scope.sortRef(sort),
    pulse: ref(c)
  }));

  return ref(v);
}

function parseSort(sort, multidomain) {
  if (sort) {
    if (!sort.field && !sort.op) {
      if (isObject(sort)) sort.field = 'key';
      else sort = {field: 'key'};
    } else if (!sort.field && sort.op !== 'count') {
      error('No field provided for sort aggregate op: ' + sort.op);
    } else if (multidomain && sort.field) {
      if (sort.op && !MULTIDOMAIN_SORT_OPS[sort.op]) {
        error('Multiple domain scales can not be sorted using ' + sort.op);
      }
    }
  }
  return sort;
}

function quantileMultipleDomain(domain, scope, fields) {
  // get value arrays for each domain field
  var values = fields.map(function(f) {
    var data = scope.getData(f.data);
    if (!data) dataLookupError(f.data);
    return data.domainRef(scope, f.field);
  });

  // combine value arrays
  return ref(scope.add(MultiValues$1({values: values})));
}

function numericMultipleDomain(domain, scope, fields) {
  // get extents for each domain field
  var extents = fields.map(function(f) {
    var data = scope.getData(f.data);
    if (!data) dataLookupError(f.data);
    return data.extentRef(scope, f.field);
  });

  // combine extents
  return ref(scope.add(MultiExtent$1({extents: extents})));
}

// -- SCALE BINS -----

function parseScaleBins(v, scope) {
  return v.signal || isArray(v)
    ? parseArray(v, scope)
    : scope.objectProperty(v);
}

// -- SCALE NICE -----

function parseScaleNice(nice) {
  return isObject(nice)
    ? {
        interval: parseLiteral(nice.interval),
        step: parseLiteral(nice.step)
      }
    : parseLiteral(nice);
}

// -- SCALE INTERPOLATION -----

function parseScaleInterpolate(interpolate, params) {
  params.interpolate = parseLiteral(interpolate.type || interpolate);
  if (interpolate.gamma != null) {
    params.interpolateGamma = parseLiteral(interpolate.gamma);
  }
}

// -- SCALE RANGE -----

function parseScaleRange(spec, scope, params) {
  var range = spec.range,
      config = scope.config.range;

  if (range.signal) {
    return scope.signalRef(range.signal);
  } else if (isString(range)) {
    if (config && hasOwnProperty(config, range)) {
      spec = extend({}, spec, {range: config[range]});
      return parseScaleRange(spec, scope, params);
    } else if (range === 'width') {
      range = [0, {signal: 'width'}];
    } else if (range === 'height') {
      range = isDiscrete(spec.type)
        ? [0, {signal: 'height'}]
        : [{signal: 'height'}, 0];
    } else {
      error('Unrecognized scale range value: ' + $(range));
    }
  } else if (range.scheme) {
    params.scheme = isArray(range.scheme)
      ? parseArray(range.scheme, scope)
      : parseLiteral(range.scheme, scope);
    if (range.extent) params.schemeExtent = parseArray(range.extent, scope);
    if (range.count) params.schemeCount = parseLiteral(range.count, scope);
    return;
  } else if (range.step) {
    params.rangeStep = parseLiteral(range.step, scope);
    return;
  } else if (isDiscrete(spec.type) && !isArray(range)) {
    return parseScaleDomain(range, spec, scope);
  } else if (!isArray(range)) {
    error('Unsupported range type: ' + $(range));
  }

  return range.map(v => (isArray(v) ? parseArray : parseLiteral)(v, scope));
}

function parseProjection(proj, scope) {
  var config = scope.config.projection || {},
      params = {};

  for (var name in proj) {
    if (name === 'name') continue;
    params[name] = parseParameter$1(proj[name], name, scope);
  }

  // apply projection defaults from config
  for (name in config) {
    if (params[name] == null) {
      params[name] = parseParameter$1(config[name], name, scope);
    }
  }

  scope.addProjection(proj.name, params);
}

function parseParameter$1(_, name, scope) {
  return isArray(_) ? _.map(function(_) { return parseParameter$1(_, name, scope); })
    : !isObject(_) ? _
    : _.signal ? scope.signalRef(_.signal)
    : name === 'fit' ? _
    : error('Unsupported parameter object: ' + $(_));
}

const Top$1 = 'top';
const Left$1 = 'left';
const Right$1 = 'right';
const Bottom$1 = 'bottom';
const Center$1 = 'center';

const Vertical = 'vertical';

const Start$1 = 'start';
const Middle$1 = 'middle';
const End$1 = 'end';

const Index  = 'index';
const Label  = 'label';
const Offset = 'offset';
const Perc   = 'perc';
const Perc2  = 'perc2';
const Size   = 'size';
const Value  = 'value';

const GuideLabelStyle = 'guide-label';
const GuideTitleStyle = 'guide-title';
const GroupTitleStyle = 'group-title';
const GroupSubtitleStyle = 'group-subtitle';

const Symbols$2 = 'symbol';
const Gradient$2 = 'gradient';
const Discrete$2 = 'discrete';

// Encoding channels supported by legends
// In priority order of 'canonical' scale
const LegendScales = [
  'size',
  'shape',
  'fill',
  'stroke',
  'strokeWidth',
  'strokeDash',
  'opacity'
];

const Skip$1 = {
  name: 1,
  style: 1,
  interactive: 1
};

const zero$1 = {value: 0};
const one$1 = {value: 1};

var Skip$2 = toSet(['rule']),
    Swap = toSet(['group', 'image', 'rect']);

function adjustSpatial(encode, marktype) {
  var code = '';

  if (Skip$2[marktype]) return code;

  if (encode.x2) {
    if (encode.x) {
      if (Swap[marktype]) {
        code += 'if(o.x>o.x2)$=o.x,o.x=o.x2,o.x2=$;';
      }
      code += 'o.width=o.x2-o.x;';
    } else {
      code += 'o.x=o.x2-(o.width||0);';
    }
  }

  if (encode.xc) {
    code += 'o.x=o.xc-(o.width||0)/2;';
  }

  if (encode.y2) {
    if (encode.y) {
      if (Swap[marktype]) {
        code += 'if(o.y>o.y2)$=o.y,o.y=o.y2,o.y2=$;';
      }
      code += 'o.height=o.y2-o.y;';
    } else {
      code += 'o.y=o.y2-(o.height||0);';
    }
  }

  if (encode.yc) {
    code += 'o.y=o.yc-(o.height||0)/2;';
  }

  return code;
}

function color$1(enc, scope, params, fields) {
  function color(type, x, y, z) {
    var a = entry$1(null, x, scope, params, fields),
        b = entry$1(null, y, scope, params, fields),
        c = entry$1(null, z, scope, params, fields);
    return 'this.' + type + '(' + [a, b, c].join(',') + ').toString()';
  }

  return (enc.c) ? color('hcl', enc.h, enc.c, enc.l)
    : (enc.h || enc.s) ? color('hsl', enc.h, enc.s, enc.l)
    : (enc.l || enc.a) ? color('lab', enc.l, enc.a, enc.b)
    : (enc.r || enc.g || enc.b) ? color('rgb', enc.r, enc.g, enc.b)
    : null;
}

function expression$1(code, scope, params, fields) {
  var expr = parseExpression$1(code, scope);
  expr.$fields.forEach(function(name) { fields[name] = 1; });
  extend(params, expr.$params);
  return expr.$expr;
}

function field$1(ref, scope, params, fields) {
  return resolve$1(isObject(ref) ? ref : {datum: ref}, scope, params, fields);
}

function resolve$1(ref, scope, params, fields) {
  var object, level, field;

  if (ref.signal) {
    object = 'datum';
    field = expression$1(ref.signal, scope, params, fields);
  } else if (ref.group || ref.parent) {
    level = Math.max(1, ref.level || 1);
    object = 'item';

    while (level-- > 0) {
      object += '.mark.group';
    }

    if (ref.parent) {
      field = ref.parent;
      object += '.datum';
    } else {
      field = ref.group;
    }
  } else if (ref.datum) {
    object = 'datum';
    field = ref.datum;
  } else {
    error('Invalid field reference: ' + $(ref));
  }

  if (!ref.signal) {
    if (isString(field)) {
      fields[field] = 1; // TODO review field tracking?
      field = splitAccessPath(field).map($).join('][');
    } else {
      field = resolve$1(field, scope, params, fields);
    }
  }

  return object + '[' + field + ']';
}

function property(property, scope, params, fields) {
  return isObject(property)
      ? '(' + entry$1(null, property, scope, params, fields) + ')'
      : property;
}

function scale$5(enc, value, scope, params, fields) {
  var scale = getScale$1(enc.scale, scope, params, fields),
      interp, func, flag;

  if (enc.range != null) {
    // pull value from scale range
    interp = +enc.range;
    func = scale + '.range()';
    value = (interp === 0) ? (func + '[0]')
      : '($=' + func + ',' + ((interp === 1) ? '$[$.length-1]'
      : '$[0]+' + interp + '*($[$.length-1]-$[0])') + ')';
  } else {
    // run value through scale and/or pull scale bandwidth
    if (value !== undefined) value = scale + '(' + value + ')';

    if (enc.band && (flag = hasBandwidth(enc.scale, scope))) {
      func = scale + '.bandwidth';

      if (enc.band.signal) {
        interp = func + '()*' + property(enc.band, scope, params, fields);
      } else {
        interp = +enc.band;
        interp = func + '()' + (interp===1 ? '' : '*' + interp);
      }

      // if we don't know the scale type, check for bandwidth
      if (flag < 0) interp = '(' + func + '?' + interp + ':0)';

      value = (value ? value + '+' : '') + interp;

      if (enc.extra) {
        // include logic to handle extraneous elements
        value = '(datum.extra?' + scale + '(datum.extra.value):' + value + ')';
      }
    }

    if (value == null) value = '0';
  }

  return value;
}

function hasBandwidth(name, scope) {
  if (!isString(name)) return -1;
  var type = scope.scaleType(name);
  return type === 'band' || type === 'point' ? 1 : 0;
}

function getScale$1(name, scope, params, fields) {
  var scaleName;

  if (isString(name)) {
    // direct scale lookup; add scale as parameter
    scaleName = ScalePrefix + name;
    if (!hasOwnProperty(params, scaleName)) {
      params[scaleName] = scope.scaleRef(name);
    }
    scaleName = $(scaleName);
  } else {
    // indirect scale lookup; add all scales as parameters
    for (scaleName in scope.scales) {
      params[ScalePrefix + scaleName] = scope.scaleRef(scaleName);
    }
    scaleName = $(ScalePrefix) + '+'
      + (name.signal
        ? '(' + expression$1(name.signal, scope, params, fields) + ')'
        : field$1(name, scope, params, fields));
  }

  return '_[' + scaleName + ']';
}

function gradient$1(enc, scope, params, fields) {
  return 'this.gradient('
    + getScale$1(enc.gradient, scope, params, fields)
    + ',' + $(enc.start)
    + ',' + $(enc.stop)
    + ',' + $(enc.count)
    + ')';
}

function entry$1(channel, enc, scope, params, fields) {
  if (enc.gradient != null) {
    return gradient$1(enc, scope, params, fields);
  }

  var value = enc.signal ? expression$1(enc.signal, scope, params, fields)
    : enc.color ? color$1(enc.color, scope, params, fields)
    : enc.field != null ? field$1(enc.field, scope, params, fields)
    : enc.value !== undefined ? $(enc.value)
    : undefined;

  if (enc.scale != null) {
    value = scale$5(enc, value, scope, params, fields);
  }

  if (value === undefined) {
    value = null;
  }

  if (enc.exponent != null) {
    value = 'Math.pow(' + value + ','
      + property(enc.exponent, scope, params, fields) + ')';
  }

  if (enc.mult != null) {
    value += '*' + property(enc.mult, scope, params, fields);
  }

  if (enc.offset != null) {
    value += '+' + property(enc.offset, scope, params, fields);
  }

  if (enc.round) {
    value = 'Math.round(' + value + ')';
  }

  return value;
}

function set$2(obj, key, value) {
  const o = obj + '[' + $(key) + ']';
  return `$=${value};if(${o}!==$)${o}=$,m=1;`;
}

function rule$1(channel, rules, scope, params, fields) {
  var code = '';

  rules.forEach(function(rule) {
    var value = entry$1(channel, rule, scope, params, fields);
    code += rule.test
      ? expression$1(rule.test, scope, params, fields) + '?' + value + ':'
      : value;
  });

  // if no else clause, terminate with null (vega/vega#1366)
  if (peek(code) === ':') {
    code += 'null';
  }

  return set$2('o', channel, code);
}

function parseEncode(encode, marktype, params, scope) {
  var fields = {},
      code = 'var o=item,datum=o.datum,m=0,$;',
      channel, enc, value;

  for (channel in encode) {
    enc = encode[channel];
    if (isArray(enc)) { // rule
      code += rule$1(channel, enc, scope, params, fields);
    } else {
      value = entry$1(channel, enc, scope, params, fields);
      code += set$2('o', channel, value);
    }
  }

  code += adjustSpatial(encode, marktype);
  code += 'return m;';

  return {
    $expr:   code,
    $fields: Object.keys(fields),
    $output: Object.keys(encode)
  };
}

var MarkRole = 'mark';
var FrameRole$1 = 'frame';
var ScopeRole$1 = 'scope';

var AxisRole$1 = 'axis';
var AxisDomainRole = 'axis-domain';
var AxisGridRole = 'axis-grid';
var AxisLabelRole = 'axis-label';
var AxisTickRole = 'axis-tick';
var AxisTitleRole = 'axis-title';

var LegendRole$1 = 'legend';
var LegendBandRole = 'legend-band';
var LegendEntryRole = 'legend-entry';
var LegendGradientRole = 'legend-gradient';
var LegendLabelRole = 'legend-label';
var LegendSymbolRole = 'legend-symbol';
var LegendTitleRole = 'legend-title';

var TitleRole$1 = 'title';
var TitleTextRole = 'title-text';
var TitleSubtitleRole = 'title-subtitle';

function encoder(_) {
  return isObject(_) && !isArray(_) ? extend({}, _) : {value: _};
}

function addEncode(object, name, value, set) {
  if (value != null) {
    if (isObject(value) && !isArray(value)) {
      object.update[name] = value;
    } else {
      object[set || 'enter'][name] = {value: value};
    }
    return 1;
  } else {
    return 0;
  }
}

function addEncoders(object, enter, update) {
  for (let name in enter) {
    addEncode(object, name, enter[name]);
  }
  for (let name in update) {
    addEncode(object, name, update[name], 'update');
  }
}

function extendEncode(encode, extra, skip) {
  for (var name in extra) {
    if (skip && hasOwnProperty(skip, name)) continue;
    encode[name] = extend(encode[name] || {}, extra[name]);
  }
  return encode;
}

function encoders(encode, type, role, style, scope, params) {
  var enc, key;
  params = params || {};
  params.encoders = {$encode: (enc = {})};

  encode = applyDefaults(encode, type, role, style, scope.config);

  for (key in encode) {
    enc[key] = parseEncode(encode[key], type, params, scope);
  }

  return params;
}

function applyDefaults(encode, type, role, style, config) {
  var defaults = {}, enter = {}, update, key, skip, props;

  // ignore legend and axis
  if (role == 'legend' || String(role).indexOf('axis') === 0) {
    role = null;
  }

  // resolve mark config
  props = role === FrameRole$1 ? config.group
    : (role === MarkRole) ? extend({}, config.mark, config[type])
    : null;

  for (key in props) {
    // do not apply defaults if relevant fields are defined
    skip = has(key, encode)
      || (key === 'fill' || key === 'stroke')
      && (has('fill', encode) || has('stroke', encode));

    if (!skip) applyDefault(defaults, key, props[key]);
  }

  // resolve styles, apply with increasing precedence
  array(style).forEach(function(name) {
    var props = config.style && config.style[name];
    for (var key in props) {
      if (!has(key, encode)) {
        applyDefault(defaults, key, props[key]);
      }
    }
  });

  encode = extend({}, encode); // defensive copy
  for (key in defaults) {
    props = defaults[key];
    if (props.signal) {
      (update = update || {})[key] = props;
    } else {
      enter[key] = props;
    }
  }

  encode.enter = extend(enter, encode.enter);
  if (update) encode.update = extend(update, encode.update);

  return encode;
}

function applyDefault(defaults, key, value) {
  defaults[key] = value && value.signal
    ? {signal: value.signal}
    : {value: value};
}

function has(key, encode) {
  return encode && (
    (encode.enter && encode.enter[key]) ||
    (encode.update && encode.update[key])
  );
}

function guideMark(type, role, style, key, dataRef, encode, extras) {
  return {
    type:  type,
    name:  extras ? extras.name : undefined,
    role:  role,
    style: (extras && extras.style) || style,
    key:   key,
    from:  dataRef,
    interactive: !!(extras && extras.interactive),
    encode: extendEncode(encode, extras, Skip$1)
  };
}

function lookup$5(spec, config) {
  const _ = (name, dflt) => value$1(spec[name], value$1(config[name], dflt));

  _.isVertical = s => Vertical === value$1(
    spec.direction,
    config.direction || (s ? config.symbolDirection : config.gradientDirection)
  );

  _.gradientLength = () => value$1(
    spec.gradientLength,
    config.gradientLength || config.gradientWidth
  );

  _.gradientThickness = () => value$1(
    spec.gradientThickness,
    config.gradientThickness || config.gradientHeight
  );

  _.entryColumns = () => value$1(
    spec.columns,
    value$1(config.columns, +_.isVertical(true))
  );

  return _;
}

function getEncoding(name, encode) {
  var v = encode && (
    (encode.update && encode.update[name]) ||
    (encode.enter && encode.enter[name])
  );
  return v && v.signal ? v : v ? v.value : null;
}

function getStyle(name, scope, style) {
  var s = scope.config.style[style];
  return s && s[name];
}

function anchorExpr(s, e, m) {
  return `item.anchor === "${Start$1}" ? ${s} : item.anchor === "${End$1}" ? ${e} : ${m}`;
}

const alignExpr = anchorExpr(
  $(Left$1),
  $(Right$1),
  $(Center$1)
);

function tickBand(_) {
  let v = _('tickBand'),
      offset = _('tickOffset'),
      band, extra;

  if (!v) {
    // if no tick band entry, fall back on other properties
    band = _('bandPosition');
    extra = _('tickExtra');
  } else if (v.signal) {
    // if signal, augment code to interpret values
    band = {signal: `(${v.signal})==='extent'?1:0.5`};
    extra = {signal: `(${v.signal})==='extent'?true:false`};
    if (!isObject(offset)) {
      offset = {signal: `(${v.signal})==='extent'?0:${offset}`};
    }
  } else if (v === 'extent') {
    // if constant, simply set values
    band = 1;
    extra = true;
    offset = 0;
  } else {
    band = 0.5;
    extra = false;
  }

  return {extra, band, offset};
}

var GroupMark = 'group';
var RectMark = 'rect';
var RuleMark = 'rule';
var SymbolMark = 'symbol';
var TextMark = 'text';

function legendGradient(spec, scale, config, userEncode) {
  var _ = lookup$5(spec, config),
      vertical = _.isVertical(),
      thickness = _.gradientThickness(),
      length = _.gradientLength(),
      encode, enter, start, stop, width, height;

  if (vertical) {
    start = [0, 1];
    stop = [0, 0];
    width = thickness;
    height = length;
  } else {
    start = [0, 0];
    stop = [1, 0];
    width = length;
    height = thickness;
  }

  encode = {
    enter: enter = {
      opacity: zero$1,
      x: zero$1,
      y: zero$1,
      width: encoder(width),
      height: encoder(height)
    },
    update: extend({}, enter, {
      opacity: one$1,
      fill: {gradient: scale, start: start, stop: stop}
    }),
    exit: {
      opacity: zero$1
    }
  };

  addEncoders(encode, {
    stroke:      _('gradientStrokeColor'),
    strokeWidth: _('gradientStrokeWidth')
  }, { // update
    opacity:     _('gradientOpacity')
  });

  return guideMark(RectMark, LegendGradientRole, null, undefined, undefined, encode, userEncode);
}

function legendGradientDiscrete(spec, scale, config, userEncode, dataRef) {
  var _ = lookup$5(spec, config),
      vertical = _.isVertical(),
      thickness = _.gradientThickness(),
      length = _.gradientLength(),
      encode, enter, u, v, uu, vv, adjust = '';

  vertical
    ? (u = 'y', uu = 'y2', v = 'x', vv = 'width', adjust = '1-')
    : (u = 'x', uu = 'x2', v = 'y', vv = 'height');

  enter = {
    opacity: zero$1,
    fill: {scale: scale, field: Value}
  };
  enter[u]  = {signal: adjust + 'datum.' + Perc, mult: length};
  enter[v]  = zero$1;
  enter[uu] = {signal: adjust + 'datum.' + Perc2, mult: length};
  enter[vv] = encoder(thickness);

  encode = {
    enter: enter,
    update: extend({}, enter, {opacity: one$1}),
    exit: {opacity: zero$1}
  };

  addEncoders(encode, {
    stroke:      _('gradientStrokeColor'),
    strokeWidth: _('gradientStrokeWidth')
  }, { // update
    opacity:     _('gradientOpacity')
  });

  return guideMark(RectMark, LegendBandRole, null, Value, dataRef, encode, userEncode);
}

const alignExpr$1 = `datum.${Perc}<=0?"${Left$1}":datum.${Perc}>=1?"${Right$1}":"${Center$1}"`,
      baselineExpr = `datum.${Perc}<=0?"${Bottom$1}":datum.${Perc}>=1?"${Top$1}":"${Middle$1}"`;

function legendGradientLabels(spec, config, userEncode, dataRef) {
  var _ = lookup$5(spec, config),
      vertical = _.isVertical(),
      thickness = encoder(_.gradientThickness()),
      length = _.gradientLength(),
      overlap = _('labelOverlap'),
      separation = _('labelSeparation'),
      encode, enter, update, u, v, adjust = '';

  encode = {
    enter: enter = {
      opacity: zero$1
    },
    update: update = {
      opacity: one$1,
      text: {field: Label}
    },
    exit: {
      opacity: zero$1
    }
  };

  addEncoders(encode, {
    fill:        _('labelColor'),
    fillOpacity: _('labelOpacity'),
    font:        _('labelFont'),
    fontSize:    _('labelFontSize'),
    fontStyle:   _('labelFontStyle'),
    fontWeight:  _('labelFontWeight'),
    limit:       value$1(spec.labelLimit, config.gradientLabelLimit)
  });

  if (vertical) {
    enter.align = {value: 'left'};
    enter.baseline = update.baseline = {signal: baselineExpr};
    u = 'y'; v = 'x'; adjust = '1-';
  } else {
    enter.align = update.align = {signal: alignExpr$1};
    enter.baseline = {value: 'top'};
    u = 'x'; v = 'y';
  }

  enter[u] = update[u] = {signal: adjust + 'datum.' + Perc, mult: length};

  enter[v] = update[v] = thickness;
  thickness.offset = value$1(spec.labelOffset, config.gradientLabelOffset) || 0;

  spec = guideMark(TextMark, LegendLabelRole, GuideLabelStyle, Value, dataRef, encode, userEncode);
  if (overlap) {
    spec.overlap = {
      separation: separation,
      method: overlap,
      order: 'datum.' + Index
    };
  }
  return spec;
}

function guideGroup(role, style, name, dataRef, interactive, encode, marks, layout) {
  return {
    type: GroupMark,
    name: name,
    role: role,
    style: style,
    from: dataRef,
    interactive: interactive || false,
    encode: encode,
    marks: marks,
    layout: layout
  };
}

// userEncode is top-level, includes entries, symbols, labels
function legendSymbolGroups(spec, config, userEncode, dataRef, columns) {
  var _ = lookup$5(spec, config),
      entries = userEncode.entries,
      interactive = !!(entries && entries.interactive),
      name = entries ? entries.name : undefined,
      height = _('clipHeight'),
      symbolOffset = _('symbolOffset'),
      valueRef = {data: 'value'},
      encode = {},
      xSignal = `${columns} ? datum.${Offset} : datum.${Size}`,
      yEncode = height ? encoder(height) : {field: Size},
      index = `datum.${Index}`,
      ncols = `max(1, ${columns})`,
      enter, update, labelOffset, symbols, labels, nrows, sort;

  yEncode.mult = 0.5;

  // -- LEGEND SYMBOLS --
  encode = {
    enter:  enter = {
      opacity: zero$1,
      x: {signal: xSignal, mult: 0.5, offset: symbolOffset},
      y: yEncode
    },
    update: update = {
      opacity: one$1,
      x: enter.x,
      y: enter.y
    },
    exit: {
      opacity: zero$1
    }
  };

  var baseFill = null,
      baseStroke = null;
  if (!spec.fill) {
    baseFill = config.symbolBaseFillColor;
    baseStroke = config.symbolBaseStrokeColor;
  }

  addEncoders(encode, {
    fill:             _('symbolFillColor', baseFill),
    shape:            _('symbolType'),
    size:             _('symbolSize'),
    stroke:           _('symbolStrokeColor', baseStroke),
    strokeDash:       _('symbolDash'),
    strokeDashOffset: _('symbolDashOffset'),
    strokeWidth:      _('symbolStrokeWidth')
  }, { // update
    opacity:          _('symbolOpacity')
  });

  LegendScales.forEach(function(scale) {
    if (spec[scale]) {
      update[scale] = enter[scale] = {scale: spec[scale], field: Value};
    }
  });

  symbols = guideMark(
    SymbolMark, LegendSymbolRole, null,
    Value, valueRef, encode, userEncode.symbols
  );
  if (height) symbols.clip = true;

  // -- LEGEND LABELS --
  labelOffset = encoder(symbolOffset);
  labelOffset.offset = _('labelOffset');

  encode = {
    enter:  enter = {
      opacity: zero$1,
      x: {signal: xSignal, offset: labelOffset},
      y: yEncode
    },
    update: update = {
      opacity: one$1,
      text: {field: Label},
      x: enter.x,
      y: enter.y
    },
    exit: {
      opacity: zero$1
    }
  };

  addEncoders(encode, {
    align:       _('labelAlign'),
    baseline:    _('labelBaseline'),
    fill:        _('labelColor'),
    fillOpacity: _('labelOpacity'),
    font:        _('labelFont'),
    fontSize:    _('labelFontSize'),
    fontStyle:   _('labelFontStyle'),
    fontWeight:  _('labelFontWeight'),
    limit:       _('labelLimit')
  });

  labels = guideMark(
    TextMark, LegendLabelRole, GuideLabelStyle,
    Value, valueRef, encode, userEncode.labels
  );

  // -- LEGEND ENTRY GROUPS --
  encode = {
    enter: {
      noBound: {value: !height}, // ignore width/height in bounds calc
      width: zero$1,
      height: height ? encoder(height) : zero$1,
      opacity: zero$1
    },
    exit: {opacity: zero$1},
    update: update = {
      opacity: one$1,
      row: {signal: null},
      column: {signal: null}
    }
  };

  // annotate and sort groups to ensure correct ordering
  if (_.isVertical(true)) {
    nrows = `ceil(item.mark.items.length / ${ncols})`;
    update.row.signal = `${index}%${nrows}`;
    update.column.signal = `floor(${index} / ${nrows})`;
    sort = {field: ['row', index]};
  } else {
    update.row.signal = `floor(${index} / ${ncols})`;
    update.column.signal = `${index} % ${ncols}`;
    sort = {field: index};
  }
  // handle zero column case (implies infinite columns)
  update.column.signal = `${columns}?${update.column.signal}:${index}`;

  // facet legend entries into sub-groups
  dataRef = {facet: {data: dataRef, name: 'value', groupby: Index}};

  spec = guideGroup(
    ScopeRole$1, null, name, dataRef, interactive,
    extendEncode(encode, entries, Skip$1), [symbols, labels]
  );
  spec.sort = sort;
  return spec;
}

function legendSymbolLayout(spec, config) {
  const _ = lookup$5(spec, config);

  // layout parameters for legend entries
  return {
    align:   _('gridAlign'),
    columns: _.entryColumns(),
    center:  {
      row: true,
      column: false
    },
    padding: {
      row:    _('rowPadding'),
      column: _('columnPadding')
    }
  };
}

// expression logic for align, anchor, angle, and baseline calculation
const isL = 'item.orient === "left"',
      isR = 'item.orient === "right"',
      isLR = `(${isL} || ${isR})`,
      isVG = `datum.vgrad && ${isLR}`,
      baseline = anchorExpr('"top"', '"bottom"', '"middle"'),
      alignFlip = anchorExpr('"right"', '"left"', '"center"'),
      exprAlign = `datum.vgrad && ${isR} ? (${alignFlip}) : (${isLR} && !(datum.vgrad && ${isL})) ? "left" : ${alignExpr}`,
      exprAnchor = `item._anchor || (${isLR} ? "middle" : "start")`,
      exprAngle = `${isVG} ? (${isL} ? -90 : 90) : 0`,
      exprBaseline = `${isLR} ? (datum.vgrad ? (${isR} ? "bottom" : "top") : ${baseline}) : "top"`;

function legendTitle(spec, config, userEncode, dataRef) {
  var _ = lookup$5(spec, config), encode;

  encode = {
    enter: {opacity: zero$1},
    update: {
      opacity: one$1,
      x: {field: {group: 'padding'}},
      y: {field: {group: 'padding'}}
    },
    exit: {opacity: zero$1}
  };

  addEncoders(encode, {
    orient:      _('titleOrient'),
    _anchor:     _('titleAnchor'),
    anchor:      {signal: exprAnchor},
    angle:       {signal: exprAngle},
    align:       {signal: exprAlign},
    baseline:    {signal: exprBaseline},
    text:        spec.title,
    fill:        _('titleColor'),
    fillOpacity: _('titleOpacity'),
    font:        _('titleFont'),
    fontSize:    _('titleFontSize'),
    fontStyle:   _('titleFontStyle'),
    fontWeight:  _('titleFontWeight'),
    limit:       _('titleLimit'),
    lineHeight:  _('titleLineHeight')
  }, { // require update
    align:       _('titleAlign'),
    baseline:    _('titleBaseline'),
  });

  return guideMark(TextMark, LegendTitleRole, GuideTitleStyle, null, dataRef, encode, userEncode);
}

function clip$2(clip, scope) {
  var expr;

  if (isObject(clip)) {
    if (clip.signal) {
      expr = clip.signal;
    } else if (clip.path) {
      expr = 'pathShape(' + param(clip.path) + ')';
    } else if (clip.sphere) {
      expr = 'geoShape(' + param(clip.sphere) + ', {type: "Sphere"})';
    }
  }

  return expr
    ? scope.signalRef(expr)
    : !!clip;
}

function param(value) {
  return isObject(value) && value.signal
    ? value.signal
    : $(value);
}

function getRole(spec) {
  var role = spec.role || '';
  return (!role.indexOf('axis') || !role.indexOf('legend') || !role.indexOf('title'))
    ? role
    : spec.type === GroupMark ? ScopeRole$1 : (role || MarkRole);
}

function definition$1(spec) {
  return {
    marktype:    spec.type,
    name:        spec.name || undefined,
    role:        spec.role || getRole(spec),
    zindex:      +spec.zindex || undefined
  };
}

function interactive(spec, scope) {
  return spec && spec.signal ? scope.signalRef(spec.signal)
    : spec === false ? false
    : true;
}

/**
 * Parse a data transform specification.
 */
function parseTransform(spec, scope) {
  var def = definition(spec.type);
  if (!def) error('Unrecognized transform type: ' + $(spec.type));

  var t = entry(def.type.toLowerCase(), null, parseParameters$1(def, spec, scope));
  if (spec.signal) scope.addSignal(spec.signal, scope.proxy(t));
  t.metadata = def.metadata || {};

  return t;
}

/**
 * Parse all parameters of a data transform.
 */
function parseParameters$1(def, spec, scope) {
  var params = {}, pdef, i, n;
  for (i=0, n=def.params.length; i<n; ++i) {
    pdef = def.params[i];
    params[pdef.name] = parseParameter$2(pdef, spec, scope);
  }
  return params;
}

/**
 * Parse a data transform parameter.
 */
function parseParameter$2(def, spec, scope) {
  var type = def.type,
      value = spec[def.name];

  if (type === 'index') {
    return parseIndexParameter(def, spec, scope);
  } else if (value === undefined) {
    if (def.required) {
      error('Missing required ' + $(spec.type)
          + ' parameter: ' + $(def.name));
    }
    return;
  } else if (type === 'param') {
    return parseSubParameters(def, spec, scope);
  } else if (type === 'projection') {
    return scope.projectionRef(spec[def.name]);
  }

  return def.array && !isSignal(value)
    ? value.map(function(v) { return parameterValue(def, v, scope); })
    : parameterValue(def, value, scope);
}

/**
 * Parse a single parameter value.
 */
function parameterValue(def, value, scope) {
  var type = def.type;

  if (isSignal(value)) {
    return isExpr$1(type) ? error('Expression references can not be signals.')
         : isField(type) ? scope.fieldRef(value)
         : isCompare(type) ? scope.compareRef(value)
         : scope.signalRef(value.signal);
  } else {
    var expr = def.expr || isField(type);
    return expr && outerExpr(value) ? scope.exprRef(value.expr, value.as)
         : expr && outerField(value) ? fieldRef(value.field, value.as)
         : isExpr$1(type) ? parseExpression$1(value, scope)
         : isData(type) ? ref(scope.getData(value).values)
         : isField(type) ? fieldRef(value)
         : isCompare(type) ? scope.compareRef(value)
         : value;
  }
}

/**
 * Parse parameter for accessing an index of another data set.
 */
function parseIndexParameter(def, spec, scope) {
  if (!isString(spec.from)) {
    error('Lookup "from" parameter must be a string literal.');
  }
  return scope.getData(spec.from).lookupRef(scope, spec.key);
}

/**
 * Parse a parameter that contains one or more sub-parameter objects.
 */
function parseSubParameters(def, spec, scope) {
  var value = spec[def.name];

  if (def.array) {
    if (!isArray(value)) { // signals not allowed!
      error('Expected an array of sub-parameters. Instead: ' + $(value));
    }
    return value.map(function(v) {
      return parseSubParameter(def, v, scope);
    });
  } else {
    return parseSubParameter(def, value, scope);
  }
}

/**
 * Parse a sub-parameter object.
 */
function parseSubParameter(def, value, scope) {
  var params, pdef, k, i, n;

  // loop over defs to find matching key
  for (i=0, n=def.params.length; i<n; ++i) {
    pdef = def.params[i];
    for (k in pdef.key) {
      if (pdef.key[k] !== value[k]) { pdef = null; break; }
    }
    if (pdef) break;
  }
  // raise error if matching key not found
  if (!pdef) error('Unsupported parameter: ' + $(value));

  // parse params, create Params transform, return ref
  params = extend(parseParameters$1(pdef, value, scope), pdef.key);
  return ref(scope.add(Params$2(params)));
}

// -- Utilities -----

function outerExpr(_) {
  return _ && _.expr;
}

function outerField(_) {
  return _ && _.field;
}

function isData(_) {
  return _ === 'data';
}

function isExpr$1(_) {
  return _ === 'expr';
}

function isField(_) {
  return _ === 'field';
}

function isCompare(_) {
  return _ === 'compare'
}

function parseData(from, group, scope) {
  var facet, key, op, dataRef, parent;

  // if no source data, generate singleton datum
  if (!from) {
    dataRef = ref(scope.add(Collect$1(null, [{}])));
  }

  // if faceted, process facet specification
  else if (facet = from.facet) {
    if (!group) error('Only group marks can be faceted.');

    // use pre-faceted source data, if available
    if (facet.field != null) {
      dataRef = parent = getDataRef(facet, scope);
    } else {
      // generate facet aggregates if no direct data specification
      if (!from.data) {
        op = parseTransform(extend({
          type:    'aggregate',
          groupby: array(facet.groupby)
        }, facet.aggregate), scope);
        op.params.key = scope.keyRef(facet.groupby);
        op.params.pulse = getDataRef(facet, scope);
        dataRef = parent = ref(scope.add(op));
      } else {
        parent = ref(scope.getData(from.data).aggregate);
      }

      key = scope.keyRef(facet.groupby, true);
    }
  }

  // if not yet defined, get source data reference
  if (!dataRef) {
    dataRef = getDataRef(from, scope);
  }

  return {
    key: key,
    pulse: dataRef,
    parent: parent
  };
}

function getDataRef(from, scope) {
  return from.$ref ? from
    : from.data && from.data.$ref ? from.data
    : ref(scope.getData(from.data).output);
}

function DataScope(scope, input, output, values, aggr) {
  this.scope = scope;   // parent scope object
  this.input = input;   // first operator in pipeline (tuple input)
  this.output = output; // last operator in pipeline (tuple output)
  this.values = values; // operator for accessing tuples (but not tuple flow)

  // last aggregate in transform pipeline
  this.aggregate = aggr;

  // lookup table of field indices
  this.index = {};
}

DataScope.fromEntries = function(scope, entries) {
  var n = entries.length,
      i = 1,
      input  = entries[0],
      values = entries[n-1],
      output = entries[n-2],
      aggr = null;

  if (input && input.type === 'load') {
    input = entries[1];
  }

  // add operator entries to this scope, wire up pulse chain
  scope.add(entries[0]);
  for (; i<n; ++i) {
    entries[i].params.pulse = ref(entries[i-1]);
    scope.add(entries[i]);
    if (entries[i].type === 'aggregate') aggr = entries[i];
  }

  return new DataScope(scope, input, output, values, aggr);
};

var prototype$1t = DataScope.prototype;

prototype$1t.countsRef = function(scope, field, sort) {
  var ds = this,
      cache = ds.counts || (ds.counts = {}),
      k = fieldKey(field), v, a, p;

  if (k != null) {
    scope = ds.scope;
    v = cache[k];
  }

  if (!v) {
    p = {
      groupby: scope.fieldRef(field, 'key'),
      pulse: ref(ds.output)
    };
    if (sort && sort.field) addSortField(scope, p, sort);
    a = scope.add(Aggregate$1(p));
    v = scope.add(Collect$1({pulse: ref(a)}));
    v = {agg: a, ref: ref(v)};
    if (k != null) cache[k] = v;
  } else if (sort && sort.field) {
    addSortField(scope, v.agg.params, sort);
  }

  return v.ref;
};

function fieldKey(field) {
  return isString(field) ? field : null;
}

function addSortField(scope, p, sort) {
  var as = aggrField(sort.op, sort.field), s;

  if (p.ops) {
    for (var i=0, n=p.as.length; i<n; ++i) {
      if (p.as[i] === as) return;
    }
  } else {
    p.ops = ['count'];
    p.fields = [null];
    p.as = ['count'];
  }
  if (sort.op) {
    p.ops.push((s=sort.op.signal) ? scope.signalRef(s) : sort.op);
    p.fields.push(scope.fieldRef(sort.field));
    p.as.push(as);
  }
}

function cache(scope, ds, name, optype, field, counts, index) {
  var cache = ds[name] || (ds[name] = {}),
      sort = sortKey(counts),
      k = fieldKey(field), v, op;

  if (k != null) {
    scope = ds.scope;
    k = k + (sort ? '|' + sort : '');
    v = cache[k];
  }

  if (!v) {
    var params = counts
      ? {field: keyFieldRef, pulse: ds.countsRef(scope, field, counts)}
      : {field: scope.fieldRef(field), pulse: ref(ds.output)};
    if (sort) params.sort = scope.sortRef(counts);
    op = scope.add(entry(optype, undefined, params));
    if (index) ds.index[field] = op;
    v = ref(op);
    if (k != null) cache[k] = v;
  }
  return v;
}

prototype$1t.tuplesRef = function() {
  return ref(this.values);
};

prototype$1t.extentRef = function(scope, field) {
  return cache(scope, this, 'extent', 'extent', field, false);
};

prototype$1t.domainRef = function(scope, field) {
  return cache(scope, this, 'domain', 'values', field, false);
};

prototype$1t.valuesRef = function(scope, field, sort) {
  return cache(scope, this, 'vals', 'values', field, sort || true);
};

prototype$1t.lookupRef = function(scope, field) {
  return cache(scope, this, 'lookup', 'tupleindex', field, false);
};

prototype$1t.indataRef = function(scope, field) {
  return cache(scope, this, 'indata', 'tupleindex', field, true, true);
};

function parseFacet(spec, scope, group) {
  var facet = spec.from.facet,
      name = facet.name,
      data = getDataRef(facet, scope),
      subscope, source, values, op;

  if (!facet.name) {
    error('Facet must have a name: ' + $(facet));
  }
  if (!facet.data) {
    error('Facet must reference a data set: ' + $(facet));
  }

  if (facet.field) {
    op = scope.add(PreFacet$1({
      field: scope.fieldRef(facet.field),
      pulse: data
    }));
  } else if (facet.groupby) {
    op = scope.add(Facet$1({
      key:   scope.keyRef(facet.groupby),
      group: ref(scope.proxy(group.parent)),
      pulse: data
    }));
  } else {
    error('Facet must specify groupby or field: ' + $(facet));
  }

  // initialize facet subscope
  subscope = scope.fork();
  source = subscope.add(Collect$1());
  values = subscope.add(Sieve$1({pulse: ref(source)}));
  subscope.addData(name, new DataScope(subscope, source, source, values));
  subscope.addSignal('parent', null);

  // parse faceted subflow
  op.params.subflow = {
    $subflow: parseSpec(spec, subscope).toRuntime()
  };
}

function parseSubflow(spec, scope, input) {
  var op = scope.add(PreFacet$1({pulse: input.pulse})),
      subscope = scope.fork();

  subscope.add(Sieve$1());
  subscope.addSignal('parent', null);

  // parse group mark subflow
  op.params.subflow = {
    $subflow: parseSpec(spec, subscope).toRuntime()
  };
}

function parseTrigger(spec, scope, name) {
  var remove = spec.remove,
      insert = spec.insert,
      toggle = spec.toggle,
      modify = spec.modify,
      values = spec.values,
      op = scope.add(operator()),
      update, expr;

  update = 'if(' + spec.trigger + ',modify("'
    + name + '",'
    + [insert, remove, toggle, modify, values]
        .map(function(_) { return _ == null ? 'null' : _; })
        .join(',')
    + '),0)';

  expr = parseExpression$1(update, scope);
  op.update = expr.$expr;
  op.params = expr.$params;
}

function parseMark(spec, scope) {
  var role = getRole(spec),
      group = spec.type === GroupMark,
      facet = spec.from && spec.from.facet,
      layout = spec.layout || role === ScopeRole$1 || role === FrameRole$1,
      nested = role === MarkRole || layout || facet,
      overlap = spec.overlap,
      ops, op, input, store, enc, bound, render, sieve, name,
      joinRef, markRef, encodeRef, layoutRef, boundRef;

  // resolve input data
  input = parseData(spec.from, group, scope);

  // data join to map tuples to visual items
  op = scope.add(DataJoin$1({
    key:   input.key || (spec.key ? fieldRef(spec.key) : undefined),
    pulse: input.pulse,
    clean: !group
  }));
  joinRef = ref(op);

  // collect visual items
  op = store = scope.add(Collect$1({pulse: joinRef}));

  // connect visual items to scenegraph
  op = scope.add(Mark$1({
    markdef:     definition$1(spec),
    interactive: interactive(spec.interactive, scope),
    clip:        clip$2(spec.clip, scope),
    context:     {$context: true},
    groups:      scope.lookup(),
    parent:      scope.signals.parent ? scope.signalRef('parent') : null,
    index:       scope.markpath(),
    pulse:       ref(op)
  }));
  markRef = ref(op);

  // add visual encoders
  op = enc = scope.add(Encode$1(encoders(
    spec.encode, spec.type, role, spec.style, scope,
    {mod: false, pulse: markRef}
  )));

  // monitor parent marks to propagate changes
  op.params.parent = scope.encode();

  // add post-encoding transforms, if defined
  if (spec.transform) {
    spec.transform.forEach(function(_) {
      const tx = parseTransform(_, scope),
            md = tx.metadata;
      if (md.generates || md.changes) {
        error('Mark transforms should not generate new data.');
      }
      if (!md.nomod) enc.params.mod = true; // update encode mod handling
      tx.params.pulse = ref(op);
      scope.add(op = tx);
    });
  }

  // if item sort specified, perform post-encoding
  if (spec.sort) {
    op = scope.add(SortItems$1({
      sort:  scope.compareRef(spec.sort),
      pulse: ref(op)
    }));
  }

  encodeRef = ref(op);

  // add view layout operator if needed
  if (facet || layout) {
    layout = scope.add(ViewLayout$1({
      layout:   scope.objectProperty(spec.layout),
      legends:  scope.legends,
      mark:     markRef,
      pulse:    encodeRef
    }));
    layoutRef = ref(layout);
  }

  // compute bounding boxes
  bound = scope.add(Bound$1({mark: markRef, pulse: layoutRef || encodeRef}));
  boundRef = ref(bound);

  // if group mark, recurse to parse nested content
  if (group) {
    // juggle layout & bounds to ensure they run *after* any faceting transforms
    if (nested) { ops = scope.operators; ops.pop(); if (layout) ops.pop(); }

    scope.pushState(encodeRef, layoutRef || boundRef, joinRef);
    facet ? parseFacet(spec, scope, input)          // explicit facet
        : nested ? parseSubflow(spec, scope, input) // standard mark group
        : parseSpec(spec, scope); // guide group, we can avoid nested scopes
    scope.popState();

    if (nested) { if (layout) ops.push(layout); ops.push(bound); }
  }

  // if requested, add overlap removal transform
  if (overlap) {
    boundRef = parseOverlap(overlap, boundRef, scope);
  }

  // render / sieve items
  render = scope.add(Render$1({pulse: boundRef}));
  sieve = scope.add(Sieve$1({pulse: ref(render)}, undefined, scope.parent()));

  // if mark is named, make accessible as reactive geometry
  // add trigger updates if defined
  if (spec.name != null) {
    name = spec.name;
    scope.addData(name, new DataScope(scope, store, render, sieve));
    if (spec.on) spec.on.forEach(function(on) {
      if (on.insert || on.remove || on.toggle) {
        error('Marks only support modify triggers.');
      }
      parseTrigger(on, scope, name);
    });
  }
}

function parseOverlap(overlap, source, scope) {
  var method = overlap.method,
      bound = overlap.bound,
      sep = overlap.separation, tol;

  var params = {
    separation: isSignal(sep) ? scope.signalRef(sep.signal) : sep,
    method: isSignal(method) ? scope.signalRef(method.signal) : method,
    pulse:  source
  };

  if (overlap.order) {
    params.sort = scope.compareRef({field: overlap.order});
  }

  if (bound) {
    tol = bound.tolerance;
    params.boundTolerance = isSignal(tol) ? scope.signalRef(tol.signal) : +tol;
    params.boundScale = scope.scaleRef(bound.scale);
    params.boundOrient = bound.orient;
  }

  return ref(scope.add(Overlap$1(params)));
}

function parseLegend(spec, scope) {
  var config = scope.config.legend,
      encode = spec.encode || {},
      legendEncode = encode.legend || {},
      name = legendEncode.name || undefined,
      interactive = legendEncode.interactive,
      style = legendEncode.style,
      _ = lookup$5(spec, config),
      entryEncode, entryLayout, params, children,
      type, datum, dataRef, entryRef, group;

  // resolve 'canonical' scale name
  var scale = LegendScales.reduce(function(a, b) { return a || spec[b]; }, 0);
  if (!scale) error('Missing valid scale for legend.');

  // resolve legend type (symbol, gradient, or discrete gradient)
  type = legendType(spec, scope.scaleType(scale));

  // single-element data source for legend group
  datum = {
    title:  spec.title != null,
    type:   type,
    vgrad:  type !== 'symbol' &&  _.isVertical()
  };
  dataRef = ref(scope.add(Collect$1(null, [datum])));

  // encoding properties for legend group
  legendEncode = extendEncode(
    buildLegendEncode(_, config), legendEncode, Skip$1
  );

  // encoding properties for legend entry sub-group
  entryEncode = {enter: {x: {value: 0}, y: {value: 0}}};

  // data source for legend values
  entryRef = ref(scope.add(LegendEntries$1(params = {
    type:    type,
    scale:   scope.scaleRef(scale),
    count:   scope.objectProperty(_('tickCount')),
    limit:   scope.property(_('symbolLimit')),
    values:  scope.objectProperty(spec.values),
    minstep: scope.property(spec.tickMinStep),
    formatType: scope.property(spec.formatType),
    formatSpecifier: scope.property(spec.format)
  })));

  // continuous gradient legend
  if (type === Gradient$2) {
    children = [
      legendGradient(spec, scale, config, encode.gradient),
      legendGradientLabels(spec, config, encode.labels, entryRef)
    ];
    // adjust default tick count based on the gradient length
    params.count = params.count || scope.signalRef(
      `max(2,2*floor((${deref(_.gradientLength())})/100))`
    );
  }

  // discrete gradient legend
  else if (type === Discrete$2) {
    children = [
      legendGradientDiscrete(spec, scale, config, encode.gradient, entryRef),
      legendGradientLabels(spec, config, encode.labels, entryRef)
    ];
  }

  // symbol legend
  else {
    // determine legend symbol group layout
    entryLayout = legendSymbolLayout(spec, config);
    children = [
      legendSymbolGroups(spec, config, encode, entryRef, deref(entryLayout.columns))
    ];
    // pass symbol size information to legend entry generator
    params.size = sizeExpression(spec, scope, children[0].marks);
  }

  // generate legend marks
  children = [
    guideGroup(LegendEntryRole, null, null, dataRef, interactive,
               entryEncode, children, entryLayout)
  ];

  // include legend title if defined
  if (datum.title) {
    children.push(legendTitle(spec, config, encode.title, dataRef));
  }

  // build legend specification
  group = guideGroup(LegendRole$1, style, name, dataRef, interactive, legendEncode, children);
  if (spec.zindex) group.zindex = spec.zindex;

  // parse legend specification
  return parseMark(group, scope);
}

function legendType(spec, scaleType) {
  var type = spec.type || Symbols$2;

  if (!spec.type && scaleCount(spec) === 1 && (spec.fill || spec.stroke)) {
    type = isContinuous(scaleType) ? Gradient$2
      : isDiscretizing(scaleType) ? Discrete$2
      : Symbols$2;
  }

  return type !== Gradient$2 ? type
    : isDiscretizing(scaleType) ? Discrete$2
    : Gradient$2;
}

function scaleCount(spec) {
  return LegendScales.reduce(function(count, type) {
    return count + (spec[type] ? 1 : 0);
  }, 0);
}

function buildLegendEncode(_, config) {
  var encode = {enter: {}, update: {}};

  addEncoders(encode, {
    orient:       _('orient'),
    offset:       _('offset'),
    padding:      _('padding'),
    titlePadding: _('titlePadding'),
    cornerRadius: _('cornerRadius'),
    fill:         _('fillColor'),
    stroke:       _('strokeColor'),
    strokeWidth:  config.strokeWidth,
    strokeDash:   config.strokeDash,
    x:            _('legendX'),
    y:            _('legendY'),
  });

  return encode;
}

function sizeExpression(spec, scope, marks) {
  var size = deref(getChannel('size', spec, marks)),
      strokeWidth = deref(getChannel('strokeWidth', spec, marks)),
      fontSize = deref(getFontSize(marks[1].encode, scope, GuideLabelStyle));

  return parseExpression$1(
    `max(ceil(sqrt(${size})+${strokeWidth}),${fontSize})`,
    scope
  );
}

function getChannel(name, spec, marks) {
  return spec[name]
    ? `scale("${spec[name]}",datum)`
    : getEncoding(name, marks[0].encode);
}

function getFontSize(encode, scope, style) {
  return getEncoding('fontSize', encode) || getStyle('fontSize', scope, style);
}

const angleExpr = `item.orient==="${Left$1}"?-90:item.orient==="${Right$1}"?90:0`;

function parseTitle(spec, scope) {
  spec = isString(spec) ? {text: spec} : spec;

  var _ = lookup$5(spec, scope.config.title),
      encode = spec.encode || {},
      userEncode = encode.group || {},
      name = userEncode.name || undefined,
      interactive = userEncode.interactive,
      style = userEncode.style,
      children = [],
      dataRef, group;

  // single-element data source for group title
  dataRef = ref(scope.add(Collect$1(null, [{}])));

  // include title text
  children.push(buildTitle(spec, _, titleEncode(spec), dataRef));

  // include subtitle text
  if (spec.subtitle) {
    children.push(buildSubTitle(spec, _, encode.subtitle, dataRef));
  }

  // build title specification
  group = guideGroup(TitleRole$1, style, name, dataRef, interactive,
                     groupEncode(_, userEncode), children);
  if (spec.zindex) group.zindex = spec.zindex;

  // parse title specification
  return parseMark(group, scope);
}

// provide backwards-compatibility for title custom encode;
// the top-level encode block has been *deprecated*.
function titleEncode(spec) {
  const encode = spec.encode;
  return (encode && encode.title) || extend({
    name: spec.name,
    interactive: spec.interactive,
    style: spec.style
  }, encode);
}

function groupEncode(_, userEncode) {
  var encode = {enter: {}, update: {}};

  addEncoders(encode, {
    orient:     _('orient'),
    anchor:     _('anchor'),
    align:      {signal: alignExpr},
    angle:      {signal: angleExpr},
    limit:      _('limit'),
    frame:      _('frame'),
    offset:     _('offset') || 0,
    padding:    _('subtitlePadding')
  });

  return extendEncode(encode, userEncode, Skip$1);
}

function buildTitle(spec, _, userEncode, dataRef) {
  var zero = {value: 0},
      text = spec.text,
      encode = {
        enter: {opacity: zero},
        update: {opacity: {value: 1}},
        exit: {opacity: zero}
      };

  addEncoders(encode, {
    text:       text,
    align:      {signal: 'item.mark.group.align'},
    angle:      {signal: 'item.mark.group.angle'},
    limit:      {signal: 'item.mark.group.limit'},
    baseline:   'top',
    dx:         _('dx'),
    dy:         _('dy'),
    fill:       _('color'),
    font:       _('font'),
    fontSize:   _('fontSize'),
    fontStyle:  _('fontStyle'),
    fontWeight: _('fontWeight'),
    lineHeight: _('lineHeight')
  }, { // update
    align:      _('align'),
    angle:      _('angle'),
    baseline:   _('baseline')
  });

  return guideMark(TextMark, TitleTextRole, GroupTitleStyle,
                   null, dataRef, encode, userEncode);
}

function buildSubTitle(spec, _, userEncode, dataRef) {
  var zero = {value: 0},
      text = spec.subtitle,
      encode = {
        enter: {opacity: zero},
        update: {opacity: {value: 1}},
        exit: {opacity: zero}
      };

  addEncoders(encode, {
    text:       text,
    align:      {signal: 'item.mark.group.align'},
    angle:      {signal: 'item.mark.group.angle'},
    limit:      {signal: 'item.mark.group.limit'},
    baseline:   'top',
    dx:         _('dx'),
    dy:         _('dy'),
    fill:       _('subtitleColor'),
    font:       _('subtitleFont'),
    fontSize:   _('subtitleFontSize'),
    fontStyle:  _('subtitleFontStyle'),
    fontWeight: _('subtitleFontWeight'),
    lineHeight: _('subtitleLineHeight')
  }, { // update
    align:      _('align'),
    angle:      _('angle'),
    baseline:   _('baseline')
  });

  return guideMark(TextMark, TitleSubtitleRole, GroupSubtitleStyle,
                   null, dataRef, encode, userEncode);
}

function parseData$1(data, scope) {
  var transforms = [];

  if (data.transform) {
    data.transform.forEach(function(tx) {
      transforms.push(parseTransform(tx, scope));
    });
  }

  if (data.on) {
    data.on.forEach(function(on) {
      parseTrigger(on, scope, data.name);
    });
  }

  scope.addDataPipeline(data.name, analyze(data, scope, transforms));
}

/**
 * Analyze a data pipeline, add needed operators.
 */
function analyze(data, scope, ops) {
  var output = [],
      source = null,
      modify = false,
      generate = false,
      upstream, i, n, t, m;

  if (data.values) {
    // hard-wired input data set
    if (hasSignal(data.values) || hasSignal(data.format)) {
      // if either values or format has signal, use dynamic loader
      output.push(load$1(scope, data));
      output.push(source = collect());
    } else {
      // otherwise, ingest upon dataflow init
      output.push(source = collect({
        $ingest: data.values,
        $format: data.format
      }));
    }
  } else if (data.url) {
    // load data from external source
    if (hasSignal(data.url) || hasSignal(data.format)) {
      // if either url or format has signal, use dynamic loader
      output.push(load$1(scope, data));
      output.push(source = collect());
    } else {
      // otherwise, request load upon dataflow init
      output.push(source = collect({
        $request: data.url,
        $format: data.format
      }));
    }
  } else if (data.source) {
    // derives from one or more other data sets
    source = upstream = array(data.source).map(function(d) {
      return ref(scope.getData(d).output);
    });
    output.push(null); // populate later
  }

  // scan data transforms, add collectors as needed
  for (i=0, n=ops.length; i<n; ++i) {
    t = ops[i];
    m = t.metadata;

    if (!source && !m.source) {
      output.push(source = collect());
    }
    output.push(t);

    if (m.generates) generate = true;
    if (m.modifies && !generate) modify = true;

    if (m.source) source = t;
    else if (m.changes) source = null;
  }

  if (upstream) {
    n = upstream.length - 1;
    output[0] = Relay$1({
      derive: modify,
      pulse: n ? upstream : upstream[0]
    });
    if (modify || n) {
      // collect derived and multi-pulse tuples
      output.splice(1, 0, collect());
    }
  }

  if (!source) output.push(collect());
  output.push(Sieve$1({}));
  return output;
}

function collect(values) {
  var s = Collect$1({}, values);
  s.metadata = {source: true};
  return s;
}

function load$1(scope, data) {
  return Load$1({
    url:    data.url ? scope.property(data.url) : undefined,
    async:  data.async ? scope.property(data.async) : undefined,
    values: data.values ? scope.property(data.values) : undefined,
    format: scope.objectProperty(data.format)
  });
}

function axisConfig(spec, scope) {
  var config = scope.config,
      orient = spec.orient,
      xy = (orient === Top$1 || orient === Bottom$1) ? config.axisX : config.axisY,
      or = config['axis' + orient[0].toUpperCase() + orient.slice(1)],
      band = scope.scaleType(spec.scale) === 'band' && config.axisBand;

  return (xy || or || band)
    ? extend({}, config.axis, xy, or, band)
    : config.axis;
}

function axisDomain(spec, config, userEncode, dataRef) {
  var _ = lookup$5(spec, config),
      orient = spec.orient,
      encode, enter, update, u, u2, v;

  encode = {
    enter: enter = {opacity: zero$1},
    update: update = {opacity: one$1},
    exit: {opacity: zero$1}
  };

  addEncoders(encode, {
    stroke:           _('domainColor'),
    strokeDash:       _('domainDash'),
    strokeDashOffset: _('domainDashOffset'),
    strokeWidth:      _('domainWidth'),
    strokeOpacity:    _('domainOpacity')
  });

  if (orient === Top$1 || orient === Bottom$1) {
    u = 'x';
    v = 'y';
  } else {
    u = 'y';
    v = 'x';
  }
  u2 = u + '2';

  enter[v] = zero$1;
  update[u] = enter[u] = position(spec, 0);
  update[u2] = enter[u2] = position(spec, 1);

  return guideMark(RuleMark, AxisDomainRole, null, null, dataRef, encode, userEncode);
}

function position(spec, pos) {
  return {scale: spec.scale, range: pos};
}

function axisGrid(spec, config, userEncode, dataRef, band) {
  var _ = lookup$5(spec, config),
      orient = spec.orient,
      vscale = spec.gridScale,
      sign = (orient === Left$1 || orient === Top$1) ? 1 : -1,
      offset = offsetValue$1(spec.offset, sign),
      encode, enter, exit, update, tickPos, u, v, v2, s;

  encode = {
    enter: enter = {opacity: zero$1},
    update: update = {opacity: one$1},
    exit: exit = {opacity: zero$1}
  };

  addEncoders(encode, {
    stroke:           _('gridColor'),
    strokeDash:       _('gridDash'),
    strokeDashOffset: _('gridDashOffset'),
    strokeOpacity:    _('gridOpacity'),
    strokeWidth:      _('gridWidth')
  });

  tickPos = {
    scale:  spec.scale,
    field:  Value,
    band:   band.band,
    extra:  band.extra,
    offset: band.offset,
    round:  _('tickRound')
  };

  if (orient === Top$1 || orient === Bottom$1) {
    u = 'x';
    v = 'y';
    s = 'height';
  } else {
    u = 'y';
    v = 'x';
    s = 'width';
  }
  v2 = v + '2';

  update[u] = enter[u] = exit[u] = tickPos;

  if (vscale) {
    update[v] = enter[v] = {scale: vscale, range: 0, mult: sign, offset: offset};
    update[v2] = enter[v2] = {scale: vscale, range: 1, mult: sign, offset: offset};
  } else {
    update[v] = enter[v] = {value: 0, offset: offset};
    update[v2] = enter[v2] = {signal: s, mult: sign, offset: offset};
  }

  return guideMark(RuleMark, AxisGridRole, null, Value, dataRef, encode, userEncode);
}

function offsetValue$1(offset, sign)  {
  if (sign === 1) ; else if (!isObject(offset)) {
    offset = sign * (offset || 0);
  } else {
    var entry = offset = extend({}, offset);

    while (entry.mult != null) {
      if (!isObject(entry.mult)) {
        entry.mult *= sign;
        return offset;
      } else {
        entry = entry.mult = extend({}, entry.mult);
      }
    }

    entry.mult = sign;
  }

  return offset;
}

function axisTicks(spec, config, userEncode, dataRef, size, band) {
  var _ = lookup$5(spec, config),
      orient = spec.orient,
      sign = (orient === Left$1 || orient === Top$1) ? -1 : 1,
      encode, enter, exit, update, tickSize, tickPos;

  encode = {
    enter: enter = {opacity: zero$1},
    update: update = {opacity: one$1},
    exit: exit = {opacity: zero$1}
  };

  addEncoders(encode, {
    stroke:           _('tickColor'),
    strokeDash:       _('tickDash'),
    strokeDashOffset: _('tickDashOffset'),
    strokeOpacity:    _('tickOpacity'),
    strokeWidth:      _('tickWidth')
  });

  tickSize = encoder(size);
  tickSize.mult = sign;

  tickPos = {
    scale:  spec.scale,
    field:  Value,
    band:   band.band,
    extra:  band.extra,
    offset: band.offset,
    round:  _('tickRound')
  };

  if (orient === Top$1 || orient === Bottom$1) {
    update.y = enter.y = zero$1;
    update.y2 = enter.y2 = tickSize;
    update.x = enter.x = exit.x = tickPos;
  } else {
    update.x = enter.x = zero$1;
    update.x2 = enter.x2 = tickSize;
    update.y = enter.y = exit.y = tickPos;
  }

  return guideMark(RuleMark, AxisTickRole, null, Value, dataRef, encode, userEncode);
}

function flushExpr(scale, threshold, a, b, c) {
  return {
    signal: 'flush(range("' + scale + '"), '
      + 'scale("' + scale + '", datum.value), '
      + threshold + ',' + a + ',' + b + ',' + c + ')'
  };
}

function axisLabels(spec, config, userEncode, dataRef, size, band) {
  var _ = lookup$5(spec, config),
      orient = spec.orient,
      sign = (orient === Left$1 || orient === Top$1) ? -1 : 1,
      isXAxis = (orient === Top$1 || orient === Bottom$1),
      scale = spec.scale,
      flush = deref(_('labelFlush')),
      flushOffset = deref(_('labelFlushOffset')),
      flushOn = flush === 0 || !!flush,
      labelAlign = _('labelAlign'),
      labelBaseline = _('labelBaseline'),
      encode, enter, tickSize, tickPos, align, baseline, offset,
      bound, overlap, separation;

  tickSize = encoder(size);
  tickSize.mult = sign;
  tickSize.offset = encoder(_('labelPadding') || 0);
  tickSize.offset.mult = sign;

  tickPos = {
    scale:  scale,
    field:  Value,
    band:   0.5,
    offset: band.offset
  };

  if (isXAxis) {
    align = labelAlign || (flushOn
      ? flushExpr(scale, flush, '"left"', '"right"', '"center"')
      : 'center');
    baseline = labelBaseline || (orient === Top$1 ? 'bottom' : 'top');
    offset = !labelAlign;
  } else {
    align = labelAlign || (orient === Right$1 ? 'left' : 'right');
    baseline = labelBaseline || (flushOn
      ? flushExpr(scale, flush, '"top"', '"bottom"', '"middle"')
      : 'middle');
    offset = !labelBaseline;
  }

  offset = offset && flushOn && flushOffset
    ? flushExpr(scale, flush, '-(' + flushOffset + ')', flushOffset, 0)
    : null;

  encode = {
    enter: enter = {
      opacity: zero$1,
      x: isXAxis ? tickPos : tickSize,
      y: isXAxis ? tickSize : tickPos
    },
    update: {
      opacity: one$1,
      text: {field: Label},
      x: enter.x,
      y: enter.y
    },
    exit: {
      opacity: zero$1,
      x: enter.x,
      y: enter.y
    }
  };

  addEncoders(encode, {
    [isXAxis ? 'dx' : 'dy']: offset,
    align:       align,
    baseline:    baseline,
    angle:       _('labelAngle'),
    fill:        _('labelColor'),
    fillOpacity: _('labelOpacity'),
    font:        _('labelFont'),
    fontSize:    _('labelFontSize'),
    fontWeight:  _('labelFontWeight'),
    fontStyle:   _('labelFontStyle'),
    limit:       _('labelLimit')
  });

  bound   = _('labelBound');
  overlap = _('labelOverlap');
  separation = _('labelSeparation');

  spec = guideMark(TextMark, AxisLabelRole, GuideLabelStyle, Value, dataRef, encode, userEncode);

  // if overlap method or bound defined, request label overlap removal
  if (overlap || bound) {
    spec.overlap = {
      separation: separation,
      method: overlap,
      order: 'datum.index',
      bound: bound ? {scale: scale, orient: orient, tolerance: bound} : null
    };
  }

  return spec;
}

function axisTitle(spec, config, userEncode, dataRef) {
  var _ = lookup$5(spec, config),
      orient = spec.orient,
      sign = (orient === Left$1 || orient === Top$1) ? -1 : 1,
      horizontal = (orient === Top$1 || orient === Bottom$1),
      encode, enter, update, titlePos;

  encode = {
    enter: enter = {
      opacity: zero$1,
      anchor: encoder(_('titleAnchor')),
      align: {signal: alignExpr}
    },
    update: update = extend({}, enter, {
      opacity: one$1,
      text: encoder(spec.title)
    }),
    exit: {
      opacity: zero$1
    }
  };

  titlePos = {
    signal: `lerp(range("${spec.scale}"), ${anchorExpr(0, 1, 0.5)})`
  };

  if (horizontal) {
    update.x = titlePos;
    enter.angle = {value: 0};
    enter.baseline = {value: orient === Top$1 ? 'bottom' : 'top'};
  } else {
    update.y = titlePos;
    enter.angle = {value: sign * 90};
    enter.baseline = {value: 'bottom'};
  }

  addEncoders(encode, {
    angle:       _('titleAngle'),
    baseline:    _('titleBaseline'),
    fill:        _('titleColor'),
    fillOpacity: _('titleOpacity'),
    font:        _('titleFont'),
    fontSize:    _('titleFontSize'),
    fontStyle:   _('titleFontStyle'),
    fontWeight:  _('titleFontWeight'),
    limit:       _('titleLimit'),
    lineHeight:  _('titleLineHeight')
  }, { // require update
    align:       _('titleAlign')
  });

  !addEncode(encode, 'x', _('titleX'), 'update')
    && !horizontal && !has('x', userEncode)
    && (encode.enter.auto = {value: true});

  !addEncode(encode, 'y', _('titleY'), 'update')
    && horizontal && !has('y', userEncode)
    && (encode.enter.auto = {value: true});

  return guideMark(TextMark, AxisTitleRole, GuideTitleStyle, null, dataRef, encode, userEncode);
}

function parseAxis(spec, scope) {
  var config = axisConfig(spec, scope),
      encode = spec.encode || {},
      axisEncode = encode.axis || {},
      name = axisEncode.name || undefined,
      interactive = axisEncode.interactive,
      style = axisEncode.style,
      _ = lookup$5(spec, config),
      band = tickBand(_),
      datum, dataRef, ticksRef, size, group, children;

  // single-element data source for axis group
  datum = {
    orient: spec.orient,
    ticks:  !!_('ticks'),
    labels: !!_('labels'),
    grid:   !!_('grid'),
    domain: !!_('domain'),
    title:  spec.title != null,
    translate: _('translate')
  };
  dataRef = ref(scope.add(Collect$1({}, [datum])));

  // encoding properties for axis group item
  axisEncode = extendEncode({
    update: {
      offset:       encoder(_('offset') || 0),
      position:     encoder(value$1(spec.position, 0)),
      titlePadding: encoder(_('titlePadding')),
      minExtent:    encoder(_('minExtent')),
      maxExtent:    encoder(_('maxExtent')),
      range:        {signal: `abs(span(range("${spec.scale}")))`}
    }
  }, encode.axis, Skip$1);

  // data source for axis ticks
  ticksRef = ref(scope.add(AxisTicks$1({
    scale:   scope.scaleRef(spec.scale),
    extra:   scope.property(band.extra),
    count:   scope.objectProperty(spec.tickCount),
    values:  scope.objectProperty(spec.values),
    minstep: scope.property(spec.tickMinStep),
    formatType: scope.property(spec.formatType),
    formatSpecifier: scope.property(spec.format)
  })));

  // generate axis marks
  children = [];

  // include axis gridlines if requested
  if (datum.grid) {
    children.push(axisGrid(spec, config, encode.grid, ticksRef, band));
  }

  // include axis ticks if requested
  if (datum.ticks) {
    size = _('tickSize');
    children.push(axisTicks(spec, config, encode.ticks, ticksRef, size, band));
  }

  // include axis labels if requested
  if (datum.labels) {
    size = datum.ticks ? size : 0;
    children.push(axisLabels(spec, config, encode.labels, ticksRef, size, band));
  }

  // include axis domain path if requested
  if (datum.domain) {
    children.push(axisDomain(spec, config, encode.domain, dataRef));
  }

  // include axis title if defined
  if (datum.title) {
    children.push(axisTitle(spec, config, encode.title, dataRef));
  }

  // build axis specification
  group = guideGroup(AxisRole$1, style, name, dataRef, interactive, axisEncode, children);
  if (spec.zindex) group.zindex = spec.zindex;

  // parse axis specification
  return parseMark(group, scope);
}

function parseSpec(spec, scope, preprocessed) {
  var signals = array(spec.signals),
      scales = array(spec.scales);

  // parse signal definitions, if not already preprocessed
  if (!preprocessed) signals.forEach(_ => parseSignal(_, scope));

  // parse cartographic projection definitions
  array(spec.projections).forEach(_ => parseProjection(_, scope));

  // initialize scale references
  scales.forEach(_ => initScale(_, scope));

  // parse data sources
  array(spec.data).forEach(_ => parseData$1(_, scope));

  // parse scale definitions
  scales.forEach(_ => parseScale(_, scope));

  // parse signal updates
  (preprocessed || signals).forEach(_ => parseSignalUpdates(_, scope));

  // parse axis definitions
  array(spec.axes).forEach(_ => parseAxis(_, scope));

  // parse mark definitions
  array(spec.marks).forEach(_ => parseMark(_, scope));

  // parse legend definitions
  array(spec.legends).forEach(_ => parseLegend(_, scope));

  // parse title, if defined
  if (spec.title) parseTitle(spec.title, scope);

  // parse collected lambda (anonymous) expressions
  scope.parseLambdas();

  return scope;
}

var defined = toSet(['width', 'height', 'padding', 'autosize']);

function parseView(spec, scope) {
  var config = scope.config,
      op, input, encode, parent, root, signals;

  scope.background = spec.background || config.background;
  scope.eventConfig = config.events;
  root = ref(scope.root = scope.add(operator()));
  scope.addSignal('width', spec.width || 0);
  scope.addSignal('height', spec.height || 0);
  scope.addSignal('padding', parsePadding(spec.padding, config));
  scope.addSignal('autosize', parseAutosize(spec.autosize, config));
  scope.legends = scope.objectProperty(config.legend && config.legend.layout);

  // parse signal definitions, including config entries
  signals = addSignals(scope, spec.signals, config.signals);

  // Store root group item
  input = scope.add(Collect$1());

  // Encode root group item
  encode = extendEncode({
    enter: { x: {value: 0}, y: {value: 0} },
    update: { width: {signal: 'width'}, height: {signal: 'height'} }
  }, spec.encode);

  encode = scope.add(Encode$1(
    encoders(encode, GroupMark, FrameRole$1, spec.style, scope, {pulse: ref(input)}))
  );

  // Perform view layout
  parent = scope.add(ViewLayout$1({
    layout:       scope.objectProperty(spec.layout),
    legends:      scope.legends,
    autosize:     scope.signalRef('autosize'),
    mark:         root,
    pulse:        ref(encode)
  }));
  scope.operators.pop();

  // Parse remainder of specification
  scope.pushState(ref(encode), ref(parent), null);
  parseSpec(spec, scope, signals);
  scope.operators.push(parent);

  // Bound / render / sieve root item
  op = scope.add(Bound$1({mark: root, pulse: ref(parent)}));
  op = scope.add(Render$1({pulse: ref(op)}));
  op = scope.add(Sieve$1({pulse: ref(op)}));

  // Track metadata for root item
  scope.addData('root', new DataScope(scope, input, input, op));

  return scope;
}

function addSignals(scope, signals, config) {
  // signals defined in the spec take priority
  array(signals).forEach(_ => {
    if (!defined[_.name]) parseSignal(_, scope);
  });

  if (!config) return signals;
  const out = array(signals).slice();

  // add config signals if not already defined
  array(config).forEach(_ => {
    if (!scope.hasOwnSignal(_.name)) {
      parseSignal(_, scope);
      out.push(_);
    }
  });

  return out;
}

function Scope$1(config) {
  this.config = config;

  this.bindings = [];
  this.field = {};
  this.signals = {};
  this.lambdas = {};
  this.scales = {};
  this.events = {};
  this.data = {};

  this.streams = [];
  this.updates = [];
  this.operators = [];
  this.background = null;
  this.eventConfig = null;

  this._id = 0;
  this._subid = 0;
  this._nextsub = [0];

  this._parent = [];
  this._encode = [];
  this._lookup = [];
  this._markpath = [];
}

function Subscope(scope) {
  this.config = scope.config;
  this.legends = scope.legends;

  this.field = Object.create(scope.field);
  this.signals = Object.create(scope.signals);
  this.lambdas = Object.create(scope.lambdas);
  this.scales = Object.create(scope.scales);
  this.events = Object.create(scope.events);
  this.data = Object.create(scope.data);

  this.streams = [];
  this.updates = [];
  this.operators = [];

  this._id = 0;
  this._subid = ++scope._nextsub[0];
  this._nextsub = scope._nextsub;

  this._parent = scope._parent.slice();
  this._encode = scope._encode.slice();
  this._lookup = scope._lookup.slice();
  this._markpath = scope._markpath;
}

var prototype$1u = Scope$1.prototype = Subscope.prototype;

// ----

prototype$1u.fork = function() {
  return new Subscope(this);
};

prototype$1u.isSubscope = function() {
  return this._subid > 0;
};

prototype$1u.toRuntime = function() {
  this.finish();
  return {
    background:  this.background,
    operators:   this.operators,
    streams:     this.streams,
    updates:     this.updates,
    bindings:    this.bindings,
    eventConfig: this.eventConfig
  };
};

prototype$1u.id = function() {
  return (this._subid ? this._subid + ':' : 0) + this._id++;
};

prototype$1u.add = function(op) {
  this.operators.push(op);
  op.id = this.id();
  // if pre-registration references exist, resolve them now
  if (op.refs) {
    op.refs.forEach(function(ref) { ref.$ref = op.id; });
    op.refs = null;
  }
  return op;
};

prototype$1u.proxy = function(op) {
  var vref = op instanceof Entry ? ref(op) : op;
  return this.add(Proxy$1({value: vref}));
};

prototype$1u.addStream = function(stream) {
  this.streams.push(stream);
  stream.id = this.id();
  return stream;
};

prototype$1u.addUpdate = function(update) {
  this.updates.push(update);
  return update;
};

// Apply metadata
prototype$1u.finish = function() {
  var name, ds;

  // annotate root
  if (this.root) this.root.root = true;

  // annotate signals
  for (name in this.signals) {
    this.signals[name].signal = name;
  }

  // annotate scales
  for (name in this.scales) {
    this.scales[name].scale = name;
  }

  // annotate data sets
  function annotate(op, name, type) {
    var data, list;
    if (op) {
      data = op.data || (op.data = {});
      list = data[name] || (data[name] = []);
      list.push(type);
    }
  }
  for (name in this.data) {
    ds = this.data[name];
    annotate(ds.input,  name, 'input');
    annotate(ds.output, name, 'output');
    annotate(ds.values, name, 'values');
    for (var field in ds.index) {
      annotate(ds.index[field], name, 'index:' + field);
    }
  }

  return this;
};

// ----

prototype$1u.pushState = function(encode, parent, lookup) {
  this._encode.push(ref(this.add(Sieve$1({pulse: encode}))));
  this._parent.push(parent);
  this._lookup.push(lookup ? ref(this.proxy(lookup)) : null);
  this._markpath.push(-1);
};

prototype$1u.popState = function() {
  this._encode.pop();
  this._parent.pop();
  this._lookup.pop();
  this._markpath.pop();
};

prototype$1u.parent = function() {
  return peek(this._parent);
};

prototype$1u.encode = function() {
  return peek(this._encode);
};

prototype$1u.lookup = function() {
  return peek(this._lookup);
};

prototype$1u.markpath = function() {
  var p = this._markpath;
  return ++p[p.length-1];
};

// ----

prototype$1u.fieldRef = function(field, name) {
  if (isString(field)) return fieldRef(field, name);
  if (!field.signal) {
    error('Unsupported field reference: ' + $(field));
  }

  var s = field.signal,
      f = this.field[s],
      params;

  if (!f) {
    params = {name: this.signalRef(s)};
    if (name) params.as = name;
    this.field[s] = f = ref(this.add(Field$1(params)));
  }
  return f;
};

prototype$1u.compareRef = function(cmp) {
  function check(_) {
    if (isSignal(_)) {
      signal = true;
      return scope.signalRef(_.signal);
    } else if (isExpr(_)) {
      signal = true;
      return scope.exprRef(_.expr);
    } else {
      return _;
    }
  }

  var scope = this,
      signal = false,
      fields = array(cmp.field).map(check),
      orders = array(cmp.order).map(check);

  return signal
    ? ref(this.add(Compare$1({fields: fields, orders: orders})))
    : compareRef(fields, orders);
};

prototype$1u.keyRef = function(fields, flat) {
  function check(_) {
    if (isSignal(_)) {
      signal = true;
      return ref(sig[_.signal]);
    } else {
      return _;
    }
  }

  var sig = this.signals,
      signal = false;
  fields = array(fields).map(check);

  return signal
    ? ref(this.add(Key$1({fields: fields, flat: flat})))
    : keyRef(fields, flat);
};

prototype$1u.sortRef = function(sort) {
  if (!sort) return sort;

  // including id ensures stable sorting
  var a = aggrField(sort.op, sort.field),
      o = sort.order || Ascending;

  return o.signal
    ? ref(this.add(Compare$1({
        fields: a,
        orders: this.signalRef(o.signal)
      })))
    : compareRef(a, o);
};

// ----

prototype$1u.event = function(source, type) {
  var key = source + ':' + type;
  if (!this.events[key]) {
    var id = this.id();
    this.streams.push({
      id: id,
      source: source,
      type: type
    });
    this.events[key] = id;
  }
  return this.events[key];
};

// ----

prototype$1u.hasOwnSignal = function(name) {
  return hasOwnProperty(this.signals, name);
};

prototype$1u.addSignal = function(name, value) {
  if (this.hasOwnSignal(name)) {
    error('Duplicate signal name: ' + $(name));
  }
  var op = value instanceof Entry ? value : this.add(operator(value));
  return this.signals[name] = op;
};

prototype$1u.getSignal = function(name) {
  if (!this.signals[name]) {
    error('Unrecognized signal name: ' + $(name));
  }
  return this.signals[name];
};

prototype$1u.signalRef = function(s) {
  if (this.signals[s]) {
    return ref(this.signals[s]);
  } else if (!hasOwnProperty(this.lambdas, s)) {
    this.lambdas[s] = this.add(operator(null));
  }
  return ref(this.lambdas[s]);
};

prototype$1u.parseLambdas = function() {
  var code = Object.keys(this.lambdas);
  for (var i=0, n=code.length; i<n; ++i) {
    var s = code[i],
        e = parseExpression$1(s, this),
        op = this.lambdas[s];
    op.params = e.$params;
    op.update = e.$expr;
  }
};

prototype$1u.property = function(spec) {
  return spec && spec.signal ? this.signalRef(spec.signal) : spec;
};

prototype$1u.objectProperty = function(spec) {
  return (!spec || !isObject(spec)) ? spec
    : this.signalRef(spec.signal || propertyLambda(spec));
};

function propertyLambda(spec) {
  return (isArray(spec) ? arrayLambda : objectLambda)(spec);
}

function arrayLambda(array) {
  var code = '[',
      i = 0,
      n = array.length,
      value;

  for (; i<n; ++i) {
    value = array[i];
    code += (i > 0 ? ',' : '')
      + (isObject(value)
        ? (value.signal || propertyLambda(value))
        : $(value));
  }
  return code + ']';
}

function objectLambda(obj) {
  var code = '{',
      i = 0,
      key, value;

  for (key in obj) {
    value = obj[key];
    code += (++i > 1 ? ',' : '')
      + $(key) + ':'
      + (isObject(value)
        ? (value.signal || propertyLambda(value))
        : $(value));
  }
  return code + '}';
}

prototype$1u.exprRef = function(code, name) {
  var params = {expr: parseExpression$1(code, this)};
  if (name) params.expr.$name = name;
  return ref(this.add(Expression$1(params)));
};

prototype$1u.addBinding = function(name, bind) {
  if (!this.bindings) {
    error('Nested signals do not support binding: ' + $(name));
  }
  this.bindings.push(extend({signal: name}, bind));
};

// ----

prototype$1u.addScaleProj = function(name, transform) {
  if (hasOwnProperty(this.scales, name)) {
    error('Duplicate scale or projection name: ' + $(name));
  }
  this.scales[name] = this.add(transform);
};

prototype$1u.addScale = function(name, params) {
  this.addScaleProj(name, Scale$1(params));
};

prototype$1u.addProjection = function(name, params) {
  this.addScaleProj(name, Projection$1(params));
};

prototype$1u.getScale = function(name) {
  if (!this.scales[name]) {
    error('Unrecognized scale name: ' + $(name));
  }
  return this.scales[name];
};

prototype$1u.projectionRef =
prototype$1u.scaleRef = function(name) {
  return ref(this.getScale(name));
};

prototype$1u.projectionType =
prototype$1u.scaleType = function(name) {
  return this.getScale(name).params.type;
};

// ----

prototype$1u.addData = function(name, dataScope) {
  if (hasOwnProperty(this.data, name)) {
    error('Duplicate data set name: ' + $(name));
  }
  return (this.data[name] = dataScope);
};

prototype$1u.getData = function(name) {
  if (!this.data[name]) {
    error('Undefined data set name: ' + $(name));
  }
  return this.data[name];
};

prototype$1u.addDataPipeline = function(name, entries) {
  if (hasOwnProperty(this.data, name)) {
    error('Duplicate data set name: ' + $(name));
  }
  return this.addData(name, DataScope.fromEntries(this, entries));
};

var defaultFont = 'sans-serif',
    defaultSymbolSize = 30,
    defaultStrokeWidth = 2,
    defaultColor = '#4c78a8',
    black = '#000',
    gray = '#888',
    lightGray = '#ddd';

/**
 * Standard configuration defaults for Vega specification parsing.
 * Users can provide their own (sub-)set of these default values
 * by passing in a config object to the top-level parse method.
 */
function defaults() {
  return {
    // default padding around visualization
    padding: 0,

    // default for automatic sizing; options: 'none', 'pad', 'fit'
    // or provide an object (e.g., {'type': 'pad', 'resize': true})
    autosize: 'pad',

    // default view background color
    // covers the entire view component
    background: null,

    // default event handling configuration
    // preventDefault for view-sourced event types except 'wheel'
    events: {
      defaults: {allow: ['wheel']}
    },

    // defaults for top-level group marks
    // accepts mark properties (fill, stroke, etc)
    // covers the data rectangle within group width/height
    group: null,

    // defaults for basic mark types
    // each subset accepts mark properties (fill, stroke, etc)
    mark: null,
    arc: { fill: defaultColor },
    area: { fill: defaultColor },
    image: null,
    line: {
      stroke: defaultColor,
      strokeWidth: defaultStrokeWidth
    },
    path: { stroke: defaultColor },
    rect: { fill: defaultColor },
    rule: { stroke: black },
    shape: { stroke: defaultColor },
    symbol: {
      fill: defaultColor,
      size: 64
    },
    text: {
      fill: black,
      font: defaultFont,
      fontSize: 11
    },

    // style definitions
    style: {
      // axis & legend labels
      'guide-label': {
        fill: black,
        font: defaultFont,
        fontSize: 10
      },
      // axis & legend titles
      'guide-title': {
        fill: black,
        font: defaultFont,
        fontSize: 11,
        fontWeight: 'bold'
      },
      // headers, including chart title
      'group-title': {
        fill: black,
        font: defaultFont,
        fontSize: 13,
        fontWeight: 'bold'
      },
      // chart subtitle
      'group-subtitle': {
        fill: black,
        font: defaultFont,
        fontSize: 12
      },
      // defaults for styled point marks in Vega-Lite
      point: {
        size: defaultSymbolSize,
        strokeWidth: defaultStrokeWidth,
        shape: 'circle'
      },
      circle: {
        size: defaultSymbolSize,
        strokeWidth: defaultStrokeWidth
      },
      square: {
        size: defaultSymbolSize,
        strokeWidth: defaultStrokeWidth,
        shape: 'square'
      },
      // defaults for styled group marks in Vega-Lite
      cell: {
        fill: 'transparent',
        stroke: lightGray
      }
    },

    // defaults for title
    title: {
      orient: 'top',
      anchor: 'middle',
      offset: 4,
      subtitlePadding: 3
    },

    // defaults for axes
    axis: {
      minExtent: 0,
      maxExtent: 200,
      bandPosition: 0.5,
      domain: true,
      domainWidth: 1,
      domainColor: gray,
      grid: false,
      gridWidth: 1,
      gridColor: lightGray,
      labels: true,
      labelAngle: 0,
      labelLimit: 180,
      labelPadding: 2,
      ticks: true,
      tickColor: gray,
      tickOffset: 0,
      tickRound: true,
      tickSize: 5,
      tickWidth: 1,
      titlePadding: 4
    },

    // correction for centering bias
    axisBand: {
      tickOffset: -0.5
    },

    // defaults for cartographic projection
    projection: {
      type: 'mercator'
    },

    // defaults for legends
    legend: {
      orient: 'right',
      padding: 0,
      gridAlign: 'each',
      columnPadding: 10,
      rowPadding: 2,
      symbolDirection: 'vertical',
      gradientDirection: 'vertical',
      gradientLength: 200,
      gradientThickness: 16,
      gradientStrokeColor: lightGray,
      gradientStrokeWidth: 0,
      gradientLabelOffset: 2,
      labelAlign: 'left',
      labelBaseline: 'middle',
      labelLimit: 160,
      labelOffset: 4,
      labelOverlap: true,
      symbolLimit: 30,
      symbolType: 'circle',
      symbolSize: 100,
      symbolOffset: 0,
      symbolStrokeWidth: 1.5,
      symbolBaseFillColor: 'transparent',
      symbolBaseStrokeColor: gray,
      titleLimit: 180,
      titleOrient: 'top',
      titlePadding: 5,
      layout: {
        offset: 18,
        direction: 'horizontal',
        left:   { direction: 'vertical' },
        right:  { direction: 'vertical' }
      }
    },

    // defaults for scale ranges
    range: {
      category: {
        scheme: 'tableau10'
      },
      ordinal: {
        scheme: 'blues'
      },
      heatmap: {
        scheme: 'yellowgreenblue'
      },
      ramp: {
        scheme: 'blues'
      },
      diverging: {
        scheme: 'blueorange',
        extent: [1, 0]
      },
      symbol: [
        'circle',
        'square',
        'triangle-up',
        'cross',
        'diamond',
        'triangle-right',
        'triangle-down',
        'triangle-left'
      ]
    }
  };
}

function parse$5(spec, config) {
  if (!isObject(spec)) {
    error('Input Vega specification must be an object.');
  }

  config = mergeConfig(defaults(), config, spec.config);
  return parseView(spec, new Scope$1(config)).toRuntime();
}

// -- Transforms -----
extend(transforms, tx, vtx, encode, geo, force, tree, reg, voronoi, wordcloud, xf);

export { Bounds, CanvasHandler, CanvasRenderer, Dataflow, Debug, Error$1 as Error, EventStream, Gradient, GroupItem, Handler, Info, Item, Marks, MultiPulse, None, Operator, Parameters, Pulse, RenderType, Renderer, ResourceLoader, SVGHandler, SVGRenderer, SVGStringRenderer, Scenegraph, Transform, View, Warn, accessor, accessorFields, accessorName, array, bandwidthNRD, bin, bootstrapCI, boundClip, context as boundContext, boundItem, boundMark, boundStroke, changeset, clampRange, closeTag, compare, constant, cumulativeLogNormal, cumulativeNormal, cumulativeUniform, debounce, definition, densityLogNormal, densityNormal, densityUniform, domChild, domClear, domCreate, domFind, dotbin, error, expressionFunction, extend, extent, extentIndex, falsy, fastmap, field, flush, font, fontFamily, fontSize, format, formats, hasOwnProperty, id, identity, inferType, inferTypes, ingest, inherits, inrange, interpolate, interpolateColors, interpolateRange, intersect, intersectBoxLine, intersectPath, intersectPoint, intersectRule, isArray, isBoolean, isDate, isFunction, isNumber, isObject, isRegExp, isString, isTuple, key, lerp, lineHeight, loader, logger, merge, mergeConfig, multiLineOffset, one, openTag, pad, panLinear, panLog, panPow, panSymlog, parse$5 as parse, curves as pathCurves, pathEqual, pathParse, vg_rect as pathRectangle, pathRender, symbols as pathSymbols, vg_trail as pathTrail, peek, point, projection, quantileLogNormal, quantileNormal, quantileUniform, quantiles, quantizeInterpolator, quarter, quartiles, random, integer as randomInteger, randomKDE, lcg as randomLCG, randomLogNormal, randomMixture, randomNormal, randomUniform, read, regressionExp, regressionLinear, regressionLoess, regressionLog, regressionPoly, regressionPow, regressionQuad, renderModule, repeat, resetSVGClipId, responseType, parse$4 as runtime, context$2 as runtimeContext, sampleCurve, sampleLogNormal, sampleNormal, sampleUniform, scale$2 as scale, sceneEqual, sceneFromJSON, pickVisit as scenePickVisit, sceneToJSON, visit as sceneVisit, zorder as sceneZOrder, scheme, setRandom, span, splitAccessPath, $ as stringValue, textMetrics, timeBin, timeFloor, timeFormat, timeInterval, timeOffset, timeSequence, timeUnitSpecifier, timeUnits, toBoolean, toDate, toNumber, toSet, toString, transform, transforms, truncate, truthy, tupleid, typeParsers, utcFloor, utcFormat, utcInterval, utcOffset, utcSequence, utcquarter, version, visitArray, writeConfig, zero, zoomLinear, zoomLog, zoomPow, zoomSymlog };