正态随机数

randomRanssian.js

var randomGaussian = function(a,b){
  var c0 = 2.515517;
  var c1 = 0.802853;
  var c2 = 0.010328;
  var d1 = 1.432788;
  var d2 = 0.189269;
  var d3 = 0.001308;

  var f = 0;
  var w = 0;
  var r = Math.random();

  if(r <= 0.5){
      w = r;
  }else{
      w = 1 - r;
  }

  if((r - 0.5) > 0){
      f = 1;
  }else if((r - 0.5) < 0){
      f = -1;
  }

  var y = Math.sqrt((-2) * Math.log(w));
  var x = f * (y - (c0 + c1 * y + c2 * y * y) / (1 + d1 * y + d2 * y * y + d3 * y * y * y));
  var z = a + x * Math.sqrt(b);

  return z;

};