@stdlib/random-strided-discrete-uniform

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Discrete Uniform Random Numbers

Fill a strided array with pseudorandom numbers drawn from a discrete uniform distribution.

Installation

npm install @stdlib/random-strided-discrete-uniform

Usage

var discreteUniform = require( '@stdlib/random-strided-discrete-uniform' );

discreteUniform( N, a, sa, b, sb, out, so[, options] )

Fills a strided array with pseudorandom numbers drawn from a discrete uniform distribution.

var Int32Array = require( '@stdlib/array-int32' );

// Create an array:
var out = new Int32Array( 10 );

// Fill the array with pseudorandom numbers:
discreteUniform( out.length, [ -10 ], 0, [ 10 ], 0, out, 1 );

The function has the following parameters:

• N: number of indexed elements.
• a: minimum support.
• sa: index increment for a.
• b: maximum support.
• sb: index increment for b.
• out: output array.
• so: index increment for out.

The N and stride parameters determine which strided array elements are accessed at runtime. For example, to access every other value in out,

var out = [ 0, 0, 0, 0, 0, 0 ];

discreteUniform( 3, [ -10 ], 0, [ 10 ], 0, out, 2 );

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Int32Array = require( '@stdlib/array-int32' );

// Initial arrays...
var a0 = new Int32Array( [ -10, -10, -10, 0, 0, 0 ] );
var b0 = new Int32Array( [ 10, 10, 10, 10, 10, 10 ] );

// Create offset views...
var a1 = new Int32Array( a0.buffer, a0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var b1 = new Int32Array( b0.buffer, b0.BYTES_PER_ELEMENT*3 ); // start at 4th element

// Create an output array:
var out = new Int32Array( 3 );

// Fill the output array:
discreteUniform( out.length, a1, -2, b1, 1, out, 1 );

The function accepts the following options:

• prng: pseudorandom number generator for generating uniformly distributed pseudorandom numbers. 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.

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

var Int32Array = require( '@stdlib/array-int32' );
var minstd = require( '@stdlib/random-base-minstd' );

var opts = {
    'prng': minstd
};

var out = new Int32Array( 10 );
discreteUniform( out.length, [ -10 ], 0, [ 10 ], 0, out, 1, opts );

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

var Int32Array = require( '@stdlib/array-int32' );

var opts = {
    'seed': 12345
};

var out = new Int32Array( 10 );
discreteUniform( out.length, [ -10 ], 0, [ 10 ], 0, out, 1, opts );

discreteUniform.ndarray( N, a, sa, oa, b, sb, ob, out, so, oo[, options] )

Fills a strided array with pseudorandom numbers drawn from a discrete uniform distribution using alternative indexing semantics.

var Int32Array = require( '@stdlib/array-int32' );

// Create an array:
var out = new Int32Array( 10 );

// Fill the array with pseudorandom numbers:
discreteUniform.ndarray( out.length, [ -10 ], 0, 0, [ 10 ], 0, 0, out, 1, 0 );

The function has the following additional parameters:

• oa: starting index for a.
• ob: starting index for b.
• oo: starting index for out.

While typed array views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to access every other value in out starting from the second value,

var out = [ 0, 0, 0, 0, 0, 0 ];

discreteUniform.ndarray( 3, [ -10 ], 0, 0, [ 10 ], 0, 0, out, 2, 1 );

The function accepts the same options as documented above for discreteUniform().

Notes

• If N <= 0, both functions leave the output array unchanged.
• Both functions support array-like objects having getter and setter accessors for array element access.

Examples

var zeros = require( '@stdlib/array-zeros' );
var zeroTo = require( '@stdlib/array-base-zero-to' );
var logEach = require( '@stdlib/console-log-each' );
var discreteUniform = require( '@stdlib/random-strided-discrete-uniform' );

// Specify a PRNG seed:
var opts = {
    'seed': 1234
};

// Create an array:
var x1 = zeros( 10, 'int32' );

// Create a list of indices:
var idx = zeroTo( x1.length );

// Fill the array with pseudorandom numbers:
discreteUniform( x1.length, [ -10 ], 0, [ 10 ], 0, x1, 1, opts );

// Create a second array:
var x2 = zeros( 10, 'generic' );

// Fill the array with the same pseudorandom numbers:
discreteUniform( x2.length, [ -10 ], 0, [ 10 ], 0, x2, 1, opts );

// Print the array contents:
logEach( 'x1[%d] = %d; x2[%d] = %d', idx, x1, idx, x2 );

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See Also

• @stdlib/random-base/discrete-uniform: discrete uniform distributed pseudorandom numbers.
• @stdlib/random-array/discrete-uniform: create an array containing pseudorandom numbers drawn from a discrete uniform distribution.
• @stdlib/random-strided/uniform: fill a strided array with pseudorandom numbers drawn from a continuous uniform distribution.

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Notice

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For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

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License

See LICENSE.

Copyright

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