485 lines
17 KiB
Markdown
485 lines
17 KiB
Markdown
# random
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> Seedable random number generator supporting many common distributions.
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[](https://www.npmjs.com/package/random) [](https://travis-ci.com/transitive-bullshit/random) [](https://standardjs.com)
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Welcome to the most **random** module on npm! 😜
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## Highlights
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- Simple API (_make easy things easy and hard things possible_)
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- Seedable based on entropy or user input
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- Plugin support for different pseudo random number generators (PRNGs)
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- Sample from many common distributions
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- uniform, normal, poisson, bernoulli, etc
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- Validates all user input via [ow](https://github.com/sindresorhus/ow)
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- Integrates with [seedrandom](https://github.com/davidbau/seedrandom)
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- Supports node >= 6 and browser
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## Install
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```bash
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npm install --save random
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```
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## Usage
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```js
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const random = require('random')
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// quick uniform shortcuts
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random.float(min = 0, max = 1) // uniform float in [ min, max )
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random.int(min = 0, max = 1) // uniform integer in [ min, max ]
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random.boolean() // true or false
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// uniform
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random.uniform(min = 0, max = 1) // () => [ min, max )
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random.uniformInt(min = 0, max = 1) // () => [ min, max ]
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random.uniformBoolean() // () => [ false, true ]
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// normal
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random.normal(mu = 0, sigma = 1)
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random.logNormal(mu = 0, sigma = 1)
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// bernoulli
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random.bernoulli(p = 0.5)
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random.binomial(n = 1, p = 0.5)
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random.geometric(p = 0.5)
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// poisson
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random.poisson(lambda = 1)
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random.exponential(lambda = 1)
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// misc
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random.irwinHall(n)
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random.bates(n)
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random.pareto(alpha)
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```
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For convenience, several common uniform samplers are exposed directly:
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```js
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random.float() // 0.2149383367670885
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random.int(0, 100) // 72
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random.boolean() // true
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```
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**All distribution methods return a thunk** (function with no params), which will return
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a series of independent, identically distributed random variables from the specified distribution.
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```js
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// create a normal distribution with default params (mu=1 and sigma=0)
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const normal = random.normal()
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normal() // 0.4855465422678824
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normal() // -0.06696771815439678
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normal() // 0.7350852689834705
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// create a poisson distribution with default params (lambda=1)
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const poisson = random.poisson()
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poisson() // 0
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poisson() // 4
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poisson() // 1
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```
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Note that returning a thunk here is more efficient when generating multiple
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samples from the same distribution.
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You can change the underlying PRNG or its seed as follows:
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```js
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const seedrandom = require('seedrandom')
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// change the underlying pseudo random number generator
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// by default, Math.random is used as the underlying PRNG
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random.use(seedrandom('foobar'))
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// create a new independent random number generator (uses seedrandom under the hood)
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const rng = random.clone('my-new-seed')
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// create a second independent random number generator and use a seeded PRNG
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const rng2 = random.clone(seedrandom('kittyfoo'))
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// replace Math.random with rng.uniform
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rng.patch()
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// restore original Math.random
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rng.unpatch()
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```
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## API
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<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
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#### Table of Contents
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- [Random](#random)
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- [rng](#rng)
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- [clone](#clone)
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- [use](#use)
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- [patch](#patch)
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- [unpatch](#unpatch)
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- [next](#next)
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- [float](#float)
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- [int](#int)
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- [integer](#integer)
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- [bool](#bool)
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- [boolean](#boolean)
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- [uniform](#uniform)
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- [uniformInt](#uniformint)
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- [uniformBoolean](#uniformboolean)
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- [normal](#normal)
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- [logNormal](#lognormal)
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- [bernoulli](#bernoulli)
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- [binomial](#binomial)
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- [geometric](#geometric)
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- [poisson](#poisson)
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- [exponential](#exponential)
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- [irwinHall](#irwinhall)
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- [bates](#bates)
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- [pareto](#pareto)
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### [Random](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L36-L382)
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Seedable random number generator supporting many common distributions.
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Defaults to Math.random as its underlying pseudorandom number generator.
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Type: `function (rng)`
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- `rng` **(RNG | [function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function))** Underlying pseudorandom number generator. (optional, default `Math.random`)
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* * *
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#### [rng](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L47-L49)
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Type: `function ()`
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* * *
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#### [clone](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L61-L67)
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- **See: RNG.clone**
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Creates a new `Random` instance, optionally specifying parameters to
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set a new seed.
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Type: `function (args, seed, opts): Random`
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- `args` **...any**
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- `seed` **[string](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String)?** Optional seed for new RNG.
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- `opts` **[object](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object)?** Optional config for new RNG options.
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* * *
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#### [use](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L87-L89)
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Sets the underlying pseudorandom number generator used via
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either an instance of `seedrandom`, a custom instance of RNG
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(for PRNG plugins), or a string specifying the PRNG to use
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along with an optional `seed` and `opts` to initialize the
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RNG.
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Type: `function (args)`
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- `args` **...any**
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Example:
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```javascript
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const random = require('random')
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random.use('example_seedrandom_string')
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// or
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random.use(seedrandom('kittens'))
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// or
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random.use(Math.random)
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```
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* * *
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#### [patch](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L94-L101)
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Patches `Math.random` with this Random instance's PRNG.
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Type: `function ()`
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* * *
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#### [unpatch](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L106-L111)
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Restores a previously patched `Math.random` to its original value.
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Type: `function ()`
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* * *
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#### [next](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L124-L126)
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Convenience wrapper around `this.rng.next()`
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Returns a floating point number in \[0, 1).
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Type: `function (): number`
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* * *
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#### [float](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L138-L140)
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Samples a uniform random floating point number, optionally specifying
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lower and upper bounds.
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Convence wrapper around `random.uniform()`
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Type: `function (min, max): number`
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- `min` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Lower bound (float, inclusive) (optional, default `0`)
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- `max` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Upper bound (float, exclusive) (optional, default `1`)
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* * *
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#### [int](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L152-L154)
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Samples a uniform random integer, optionally specifying lower and upper
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bounds.
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Convence wrapper around `random.uniformInt()`
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Type: `function (min, max): number`
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- `min` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Lower bound (integer, inclusive) (optional, default `0`)
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- `max` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Upper bound (integer, inclusive) (optional, default `1`)
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* * *
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#### [integer](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L168-L170)
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Samples a uniform random integer, optionally specifying lower and upper
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bounds.
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Convence wrapper around `random.uniformInt()`
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Type: `function (min, max): number`
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- `min` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Lower bound (integer, inclusive) (optional, default `0`)
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- `max` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Upper bound (integer, inclusive) (optional, default `1`)
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* * *
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#### [bool](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L181-L183)
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Samples a uniform random boolean value.
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Convence wrapper around `random.uniformBoolean()`
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Type: `function (): boolean`
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* * *
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#### [boolean](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L192-L194)
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Samples a uniform random boolean value.
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Convence wrapper around `random.uniformBoolean()`
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Type: `function (): boolean`
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* * *
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#### [uniform](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L207-L209)
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Generates a [Continuous uniform distribution](https://en.wikipedia.org/wiki/Uniform_distribution_(continuous)).
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Type: `function (min, max): function`
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- `min` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Lower bound (float, inclusive) (optional, default `0`)
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- `max` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Upper bound (float, exclusive) (optional, default `1`)
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* * *
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#### [uniformInt](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L218-L220)
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Generates a [Discrete uniform distribution](https://en.wikipedia.org/wiki/Discrete_uniform_distribution).
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Type: `function (min, max): function`
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- `min` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Lower bound (integer, inclusive) (optional, default `0`)
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- `max` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Upper bound (integer, inclusive) (optional, default `1`)
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* * *
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#### [uniformBoolean](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L230-L232)
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Generates a [Discrete uniform distribution](https://en.wikipedia.org/wiki/Discrete_uniform_distribution),
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with two possible outcomes, `true` or \`false.
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This method is analogous to flipping a coin.
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Type: `function (): function`
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* * *
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#### [normal](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L245-L247)
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Generates a [Normal distribution](https://en.wikipedia.org/wiki/Normal_distribution).
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Type: `function (mu, sigma): function`
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- `mu` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Mean (optional, default `0`)
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- `sigma` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Standard deviation (optional, default `1`)
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* * *
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#### [logNormal](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L256-L258)
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Generates a [Log-normal distribution](https://en.wikipedia.org/wiki/Log-normal_distribution).
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Type: `function (mu, sigma): function`
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- `mu` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Mean of underlying normal distribution (optional, default `0`)
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- `sigma` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Standard deviation of underlying normal distribution (optional, default `1`)
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* * *
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#### [bernoulli](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L270-L272)
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Generates a [Bernoulli distribution](https://en.wikipedia.org/wiki/Bernoulli_distribution).
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Type: `function (p): function`
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- `p` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Success probability of each trial. (optional, default `0.5`)
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* * *
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#### [binomial](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L281-L283)
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Generates a [Binomial distribution](https://en.wikipedia.org/wiki/Binomial_distribution).
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Type: `function (n, p): function`
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- `n` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Number of trials. (optional, default `1`)
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- `p` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Success probability of each trial. (optional, default `0.5`)
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* * *
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#### [geometric](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L291-L293)
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Generates a [Geometric distribution](https://en.wikipedia.org/wiki/Geometric_distribution).
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Type: `function (p): function`
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- `p` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Success probability of each trial. (optional, default `0.5`)
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* * *
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#### [poisson](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L305-L307)
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Generates a [Poisson distribution](https://en.wikipedia.org/wiki/Poisson_distribution).
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Type: `function (lambda): function`
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- `lambda` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Mean (lambda > 0) (optional, default `1`)
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* * *
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#### [exponential](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L315-L317)
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Generates an [Exponential distribution](https://en.wikipedia.org/wiki/Exponential_distribution).
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Type: `function (lambda): function`
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- `lambda` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Inverse mean (lambda > 0) (optional, default `1`)
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* * *
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#### [irwinHall](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L329-L331)
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Generates an [Irwin Hall distribution](https://en.wikipedia.org/wiki/Irwin%E2%80%93Hall_distribution).
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Type: `function (n): function`
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- `n` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Number of uniform samples to sum (n >= 0) (optional, default `1`)
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* * *
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#### [bates](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L339-L341)
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Generates a [Bates distribution](https://en.wikipedia.org/wiki/Bates_distribution).
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Type: `function (n): function`
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- `n` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Number of uniform samples to average (n >= 1) (optional, default `1`)
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* * *
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#### [pareto](https://github.com/transitive-bullshit/random/blob/e11a840a1cfe0f5bd9c43640f9645a0b28f61406/src/random.js#L349-L351)
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Generates a [Pareto distribution](https://en.wikipedia.org/wiki/Pareto_distribution).
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Type: `function (alpha): function`
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- `alpha` **[number](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number)** Alpha (optional, default `1`)
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* * *
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## Todo
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- Distributions
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- [x] uniform
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- [x] uniformInt
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- [x] uniformBoolean
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- [x] normal
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- [x] logNormal
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- [ ] chiSquared
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- [ ] cauchy
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- [ ] fischerF
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- [ ] studentT
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- [x] bernoulli
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- [x] binomial
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- [ ] negativeBinomial
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- [x] geometric
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- [x] poisson
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- [x] exponential
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- [ ] gamma
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- [ ] hyperExponential
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- [ ] weibull
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- [ ] beta
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- [ ] laplace
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- [x] irwinHall
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- [x] bates
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- [x] pareto
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- Generators
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- [x] pluggable prng
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- [ ] port more prng from boost
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- [ ] custom entropy
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- Misc
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- [x] browser support via rollup
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- [x] basic docs
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- [x] basic tests
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- [x] test suite
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- [x] initial release!
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## Related
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- [d3-random](https://github.com/d3/d3-random) - D3's excellent random number generation library.
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- [seedrandom](https://github.com/davidbau/seedrandom) - Seedable pseudo random number generator.
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- [random-int](https://github.com/sindresorhus/random-int) - For the common use case of generating uniform random ints.
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- [random-float](https://github.com/sindresorhus/random-float) - For the common use case of generating uniform random floats.
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- [randombytes](https://github.com/crypto-browserify/randombytes) - Random crypto bytes for Node.js and the browser.
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## Credit
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Huge shoutout to [Roger Combs](https://github.com/rcombs) for donating the `random` npm package for this project!
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Lots of inspiration from [d3-random](https://github.com/d3/d3-random) ([@mbostock](https://github.com/mbostock) and [@svanschooten](https://github.com/svanschooten)).
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Some distributions and PRNGs are ported from C++ [boost::random](https://www.boost.org/doc/libs/1_66_0/doc/html/boost_random/reference.html#boost_random.reference.distributions).
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## License
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MIT © [Travis Fischer](https://github.com/transitive-bullshit)
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