Chi-square Random Numbers

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Chi-square Random Numbers

Create an array containing pseudorandom numbers drawn from a chi-square distribution.

Installation

npm install @stdlib/random-array-chisquare

Alternatively,

To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
If you are using Deno, visit the deno branch (see README for usage intructions).
For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var chisquare = require( '@stdlib/random-array-chisquare' );

chisquare( len, k[, options] )

Returns an array containing pseudorandom numbers drawn from a chi-square distribution.

var out = chisquare( 10, 2.0 );
// returns <Float64Array>

The function has the following parameters:

len: output array length.
k: degrees of freedom.
options: function options.

The function accepts the following options:

dtype: output array data type. Must be a real-valued floating-point data type or "generic". Default: 'float64'.

By default, the function returns a Float64Array. To return an array having a different data type, set the dtype option.

var opts = {
    'dtype': 'generic'
};

var out = chisquare( 10, 2.0, opts );
// returns [...]

chisquare.assign( k, out )

Fills an array with pseudorandom numbers drawn from a chi-square distribution.

var zeros = require( '@stdlib/array-zeros' );

var x = zeros( 10, 'float64' );
// returns <Float64Array>

var out = chisquare.assign( 2.0, x );
// returns <Float64Array>

var bool = ( out === x );
// returns true

The function has the following parameters:

k: degrees of freedom.
out: output array.

chisquare.factory( [k, ][options] )

Returns a function for creating arrays containing pseudorandom numbers drawn from a chi-square distribution.

var random = chisquare.factory();

var out = random( 10, 2.0 );
// returns <Float64Array>

var len = out.length;
// returns 10

If provided k, the returned generator returns random variates from the specified distribution.

var random = chisquare.factory( 2.0 );

var out = random( 10 );
// returns <Float64Array>

out = random( 10 );
// returns <Float64Array>

If not provided k, the returned generator requires that k be provided at each invocation.

var random = chisquare.factory();

var out = random( 10, 2.0 );
// returns <Float64Array>

out = random( 10, 2.0 );
// returns <Float64Array>

The function accepts the following options:

prng: pseudorandom number generator for generating uniformly distributed pseudorandom numbers on the interval [0,1). If provided, the function ignores both the state and seed options. In order to seed the underlying pseudorandom number generator, one must seed the provided prng (assuming the provided prng is seedable).
seed: pseudorandom number generator seed.
state: a Uint32Array containing pseudorandom number generator state. If provided, the function ignores the seed option.
copy: boolean indicating whether to copy a provided pseudorandom number generator state. Setting this option to false allows sharing state between two or more pseudorandom number generators. Setting this option to true ensures that an underlying generator has exclusive control over its internal state. Default: true.
dtype: default output array data type. Must be a real-valued floating-point data type or "generic". Default: 'float64'.

To use a custom PRNG as the underlying source of uniformly distributed pseudorandom numbers, set the prng option.

var minstd = require( '@stdlib/random-base-minstd' );

var opts = {
    'prng': minstd.normalized
};
var random = chisquare.factory( 2.0, opts );

var out = random( 10 );
// returns <Float64Array>

To seed the underlying pseudorandom number generator, set the seed option.

var opts = {
    'seed': 12345
};
var random = chisquare.factory( 2.0, opts );

var out = random( 10, opts );
// returns <Float64Array>

The returned function accepts the following options:

dtype: output array data type. Must be a real-valued floating-point data type or "generic". This overrides the default output array data type.

To override the default output array data type, set the dtype option.

var random = chisquare.factory( 2.0 );

var out = random( 10 );
// returns <Float64Array>

var opts = {
    'dtype': 'generic'
};
out = random( 10, opts );
// returns [...]

chisquare.PRNG

The underlying pseudorandom number generator.

var prng = chisquare.PRNG;
// returns <Function>