Download the latest compiled version of stochator.js (0.3.0).
Stochator is a tiny library providing for creating a variety of random value generators.
To create a Stochator object, simply invoke the constructor and pass it an options object with a kind property. If not provided, kind is 'float'.
Valid kinds include float, integer, set, color, a-z and A-Z.
It's very easy generate a float between 0 and 1.
var generator = new Stochator({});
generator.next(); // 0.9854211050551385
generator.next(); // 0.8784450970124453
generator.next(); // 0.1592887439765036This is not very exciting because it simply wraps the built-in Math.random method.
Specifying a min and a max allows us to create random numbers in the interval (min, max), not inclusive.
var radianGenerator = new Stochator({
min: 0,
max: Math.PI * 2
});
radianGenerator.next(); // 3.7084574239999655
radianGenerator.next(); // 1.021138034566463
radianGenerator.next(); // 4.012664264853087We can also generate random floats from a normal distribution. Min and max are optional, and when provided will result in truncation of all results outside of [min, max].
var testScores = new Stochator({
mean: 75,
stdev: 14,
min: 0,
max: 100
});
testScores.next(); // 59.437160028200125
testScores.next(); // 80.18612670399554
testScores.next(); // 75.81242027226946For integers, the interval [min, max] is inclusive. Notice that the optional argument name allows us to alias next to a more descriptive method name.
var die = new Stochator({
kind: "integer",
min: 1,
max: 6
}, "roll");
die.roll(); // 6
die.roll(); // 1
die.roll(); // 2If the next method (or a method aliased to it) is passed an integer n, it will return an n-length array of results. Using the die instance from the previous example:
die.roll(1); // [5]
die.roll(2); // [5, 3]
die.roll(5); // [6, 3, 6, 6, 5]We can generate random values from arbitary sets.
var dayGenerator = new Stochator({
kind: "set",
values: ["monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday"]
});
dayGenerator.next(); // friday
dayGenerator.next(); // monday
dayGenerator.next(); // mondayWhat if we favor the weekend? Well, we can pass weights, an array of the same length as values consisting of probabilities out of 1 that correspond to values.
var biasedDayGenerator = new Stochator({
kind: "set",
values: ["monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday"],
weights: [0.1, 0.1, 0.1, 0.1, 0.1, 0.25, 0.25]
});
biasedDayGenerator.next(); // thursday
biasedDayGenerator.next(); // sunday
biasedDayGenerator.next(); // saturdayPassing a replacement property with a falsy value will result in each random
value generation to be removed from the set.
var chores = new Stochator({
kind: "set",
values: ["floors", "windows", "dishes"],
replacement: false
});
var myChore = chores.next(); // "windows"
var yourChore = chores.next(); // "floors"
var hisChore = chores.next(); // "dishes"
var noOnesChore = chores.next() // undefinedAt present, predefined sets include "a-z", "A-Z" and "color".
var colorGenerator = new Stochator({
kind: "color"
});
colorGenerator.next(); // { red: 122, green: 200, blue: 121 }
colorGenerator.next(); // { red: 129, green: 89, blue: 192 }
colorGenerator.next(); // { red: 125, green: 211, blue: 152 }
var characterGenerator = new Stochator({
kind: "a-z"
});
characterGenerator.next(); // r
characterGenerator.next(); // j
characterGenerator.next(); // uThe constructor accepts an optional final argument which is passed the output of the random value generator. Its return value becomes the return value of next or its alias. To generate random boolean values, we can do:
var booleanGenerator = new Stochator({
kind: "integer",
min: 0,
max: 1
}, Boolean);
booleanGenerator.next(); // false
booleanGenerator.next(); // true
booleanGenerator.next(); // trueWe can map the previously mentioned radianGenerator to the cosine of its values.
var radianSineGenerator = new Stochator({
min: 0,
max: Math.PI * 2
}, Math.cos);
radianSineGenerator.next(); // -0.31173382958096524
radianSineGenerator.next(); // -0.6424354006937544
radianSineGenerator.next(); // 0.6475980728835664Mutators remember their previous result and, at each generation, apply the results of a specified stochator to create a new result.
(This is functionally equivalent to a Markov chain.)
var drunkardsWalk = new Stochator({
kind: "integer",
min: -1,
max: 1
}, function(a, b) { return a + b; });
drunkardsWalk.value = 0; // Sets the initial value
drunkardsWalk.next(10); // [-1, -2, -2, -1, -1, -1, 0, 1, 1, 2]
drunkardsWalk.next(10); // [3, 3, 3, 2, 1, 0, -1, 0, 0, 0]
drunkardsWalk.next(10); // [0, 1, 0, -1, 0, 0, 1, 2, 1, 1]Let's model a bank account's balance. How much money might you have after 10 years if you start with $1000, add $1000 every year, and get interest at a random rate between 1% and 5%?
var addInterest = function(interestRate, principal) {
return (principal + 1000) * interestRate;
};
var savingsAccountBalance = new Stochator({
kind: "float",
min: 1.01,
max: 1.05
}, addInterest);
savingsAccountBalance.value = 1000; // Sets the initital value
savingsAccountBalance.next(10);
/*
[
2096.2402432970703,
3177.3792999428224,
4339.349049328612,
5441.863800747634,
6507.916293297546,
7669.519280743041,
9011.783840249629,
10225.82489660009,
11630.122217972781,
12782.667463879243
]
*/If the Stochator constructor is passed multiple configuration objects, next (or its alias) returns an array of each random generated value.
To generate a random point, we might do:
var x = { kind: 'integer', min: 0, max: 480 };
var y = { kind: 'integer', min: 0, max: 360 };
var mutator = function(values) {
return {
x: values[0],
y: values[1]
};
};
var randomPoint = new Stochator(x, y, mutator);
randomPoint.next() // { x: 79, y: 65 }
randomPoint.next() // { x: 151, y: 283 }
randomPoint.next() // { x: 5, y: 253 }
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