StackGenVis/frontend/node_modules/circumcenter/circumcenter.js

"use strict"

var dup = require("dup")
var solve = require("robust-linear-solve")

function dot(a, b) {
  var s = 0.0
  var d = a.length
  for(var i=0; i<d; ++i) {
    s += a[i] * b[i]
  }
  return s
}

function barycentricCircumcenter(points) {
  var N = points.length
  if(N === 0) {
    return []
  }
  
  var D = points[0].length
  var A = dup([points.length+1, points.length+1], 1.0)
  var b = dup([points.length+1], 1.0)
  A[N][N] = 0.0
  for(var i=0; i<N; ++i) {
    for(var j=0; j<=i; ++j) {
      A[j][i] = A[i][j] = 2.0 * dot(points[i], points[j])
    }
    b[i] = dot(points[i], points[i])
  }
  var x = solve(A, b)

  var denom = 0.0
  var h = x[N+1]
  for(var i=0; i<h.length; ++i) {
    denom += h[i]
  }

  var y = new Array(N)
  for(var i=0; i<N; ++i) {
    var h = x[i]
    var numer = 0.0
    for(var j=0; j<h.length; ++j) {
      numer += h[j]
    }
    y[i] =  numer / denom
  }

  return y
}

function circumcenter(points) {
  if(points.length === 0) {
    return []
  }
  var D = points[0].length
  var result = dup([D])
  var weights = barycentricCircumcenter(points)
  for(var i=0; i<points.length; ++i) {
    for(var j=0; j<D; ++j) {
      result[j] += points[i][j] * weights[i]
    }
  }
  return result
}

circumcenter.barycenetric = barycentricCircumcenter
module.exports = circumcenter