mathjs/test/function/probability/random.js

var assert = require('assert'),
    _ = require('underscore'),
    math = require('../../../math.js');

var testRandom = function() {
    var picked = [], count

    _.times(1000, function() {
        picked.push(math.random(-10, 10))
    })

    count = _.filter(picked, function(val) { return val < -10 }).length
    assert.equal(count, 0)
    count = _.filter(picked, function(val) { return val > 10 }).length
    assert.equal(count, 0)

    count = _.filter(picked, function(val) { return val < -8 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val >= -8 && val < -6 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val >= -6 && val < -4 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val >= -4 && val < -2 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val >= -2 && val < 0 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val >= 0 && val < 2 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val >= 2 && val < 4 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val >= 4 && val < 6 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val >= 6 && val < 8 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val >= 8 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
}

var testRandomInt = function() {
    var picked = []
      , count

    _.times(1000, function() {
        picked.push(math.randomInt(-15, -5))
    })

    picked.forEach(function(val) {
        assert.ok(_.contains([-15, -14, -13, -12, -11, -10, -9, -8, -7, -6], val))
    })

    count = _.filter(picked, function(val) { return val === -15 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val === -14 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val === -13 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val === -12 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val === -11 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val === -10 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val === -9 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val === -8 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val === -7 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)
    count = _.filter(picked, function(val) { return val === -6 }).length
    assert.equal(math.round(count/picked.length, 1), 0.1)

}

var testPickRandom = function() {
    var possibles = [11, 22, 33, 44, 55],
        picked = [],
        count

    _.times(1000, function() {
        picked.push(math.pickRandom(possibles))
    })

    count = _.filter(picked, function(val) { return val === 11 }).length
    assert.equal(math.round(count/picked.length, 1), 0.2)

    count = _.filter(picked, function(val) { return val === 22 }).length
    assert.equal(math.round(count/picked.length, 1), 0.2)

    count = _.filter(picked, function(val) { return val === 33 }).length
    assert.equal(math.round(count/picked.length, 1), 0.2)

    count = _.filter(picked, function(val) { return val === 44 }).length
    assert.equal(math.round(count/picked.length, 1), 0.2)

    count = _.filter(picked, function(val) { return val === 55 }).length
    assert.equal(math.round(count/picked.length, 1), 0.2)
}

var assertInTolerance = function(testVal, val, tol) {
    var diff = Math.abs(val - testVal) 
    if (diff > tol) assert.equal(testVal, val) 
    else assert.ok(diff <= tol)
}

var testRandomNormal = function() {
    var picked = [], count, distribution = math.distribution('normal')

    _.times(100000, function() {
        picked.push(distribution.random())
    })
    count = _.filter(picked, function(val) { return val < 0 }).length
    assert.equal(count, 0)
    count = _.filter(picked, function(val) { return val > 1 }).length
    assert.equal(count, 0)

    count = _.filter(picked, function(val) { return val < 0.25 }).length
    assertInTolerance(count/picked.length, 0.07, 0.01)
    count = _.filter(picked, function(val) { return val < 0.4 }).length
    assertInTolerance(count/picked.length, 0.27, 0.01)
    count = _.filter(picked, function(val) { return val < 0.5 }).length
    assertInTolerance(count/picked.length, 0.5, 0.01)
    count = _.filter(picked, function(val) { return val < 0.6 }).length
    assertInTolerance(count/picked.length, 0.73, 0.01)
    count = _.filter(picked, function(val) { return val < 0.75 }).length
    assertInTolerance(count/picked.length, 0.93, 0.01)
}

testRandom()
testRandomInt()
testPickRandom()

testRandomNormal()