mirror of
https://github.com/josdejong/mathjs.git
synced 2026-01-25 15:07:57 +00:00
103 lines
3.4 KiB
JavaScript
103 lines
3.4 KiB
JavaScript
/**
|
|
* Return a random number between 0 and 1
|
|
*
|
|
* random()
|
|
*
|
|
* @return {Number} res
|
|
*/
|
|
|
|
// Each distribution is a function that takes no argument and when called returns
|
|
// a number between 0 and 1.
|
|
var distributions = {
|
|
|
|
uniform: function() {
|
|
return Math.random;
|
|
},
|
|
|
|
// Implementation of normal distribution using Box-Muller transform
|
|
// ref : http://en.wikipedia.org/wiki/Box%E2%80%93Muller_transform
|
|
// We take : mean = 0.5, standard deviation = 1/6
|
|
// so that 99.7% values are in [0, 1].
|
|
normal: function() {
|
|
return function() {
|
|
var u1, u2,
|
|
picked = -1
|
|
// We reject values outside of the interval [0, 1]
|
|
// TODO: check if it is ok to do that?
|
|
while (picked < 0 || picked > 1) {
|
|
u1 = Math.random();
|
|
u2 = Math.random();
|
|
picked = 1/6 * Math.pow(-2 * Math.log(u1), 0.5) * Math.cos(2 * Math.PI * u2) + 0.5;
|
|
}
|
|
return picked;
|
|
}
|
|
}
|
|
};
|
|
|
|
math.distribution = function(name) {
|
|
if (!distributions.hasOwnProperty(name))
|
|
throw new Error('unknown distribution ' + name);
|
|
|
|
var args = Array.prototype.slice.call(arguments, 1),
|
|
distribution = distributions[name].apply(this, args);
|
|
|
|
// We wrap all the random functions into one object which uses the given distribution.
|
|
return (function(distribution) {
|
|
|
|
var randFunctions = {
|
|
|
|
random: function(min, max) {
|
|
if (arguments.length > 2)
|
|
newArgumentsError('random', arguments.length, 0, 2);
|
|
if (max === undefined) max = 1
|
|
if (min === undefined) min = 0
|
|
return min + distribution() * (max - min);
|
|
},
|
|
|
|
randomInt: function(min, max) {
|
|
if (arguments.length > 2)
|
|
newArgumentsError('randomInt', arguments.length, 0, 2);
|
|
return Math.floor(this.random(min, max));
|
|
},
|
|
|
|
pickRandom: function(possibles) {
|
|
if (arguments.length !== 1)
|
|
newArgumentsError('pickRandom', arguments.length, 1);
|
|
return possibles[Math.floor(Math.random() * possibles.length)];
|
|
},
|
|
|
|
randomMatrix: function(size, min, max) {
|
|
if (arguments.length > 3 || arguments.length < 1)
|
|
newArgumentsError('pickRandom', arguments.length, 1, 3);
|
|
debugger
|
|
return new Matrix(_randomDataForMatrix(size, min, max));
|
|
}
|
|
};
|
|
|
|
var _randomDataForMatrix = function(size, min, max) {
|
|
var data = [], length, i;
|
|
size = size.slice(0);
|
|
|
|
if (size.length > 1) {
|
|
for (i = 0, length = size.shift(); i < length; i++)
|
|
data.push(_randomDataForMatrix(size, min, max));
|
|
} else {
|
|
for (i = 0, length = size.shift(); i < length; i++)
|
|
data.push(randFunctions.random.call(randFunctions, min, max));
|
|
}
|
|
|
|
return data;
|
|
};
|
|
|
|
return randFunctions;
|
|
|
|
})(distribution);
|
|
|
|
};
|
|
|
|
// Default random functions use uniform distribution
|
|
var uniformRandFunctions = math.distribution('uniform');
|
|
math.random = uniformRandFunctions.random;
|
|
math.randomInt = uniformRandFunctions.randomInt;
|
|
math.pickRandom = uniformRandFunctions.pickRandom;
|
|
math.randomMatrix = uniformRandFunctions.randomMatrix; |