math-extras/lib/math-extras.js

Useful mathematical functions which should be part of the JavaScript Math object.

(function() {
  Math.radians = function(degrees) {
    return degrees * Math.PI / 180;
  };

  Math.degrees = function(radians) {
    return radians * 180 / Math.PI;
  };

  Math.sign = function(num) {
    if (num) {
      if (num < 0) {
        return -1;
      } else {
        return 1;
      }
    } else {
      return 0;
    }
  };

  Math.factorial = function(x) {
    if (x < 2) {
      return 1;
    } else {
      return Math.factorial(x - 1) * x;
    }
  };

  Math.log10 = function(x) {
    return Math.log(x) / Math.LN10;
  };

  Math.erf = function(x) {
    var a1, a2, a3, a4, a5, p, sign, t, y;
    a1 = 0.254829592;
    a2 = -0.284496736;
    a3 = 1.421413741;
    a4 = -1.453152027;
    a5 = 1.061405429;
    p = 0.3275911;
    sign = 1;
    if (x < 0) {
      sign = -1;
    }
    x = Math.abs(x);
    t = 1.0 / (1.0 + p * x);
    y = 1.0 - (((((a5 * t + a4) * t) + a3) * t + a2) * t + a1) * t * Math.exp(-x * x);
    return sign * y;
  };

}).call(this);