randu

Fill a strided array with uniformly distributed pseudorandom numbers between 0 and 1.

Usage

var randu = require( '@stdlib/random/strided/randu' );

randu( N, out, so[, options] )

Fills a strided array with uniformly distributed pseudorandom numbers between 0 and 1.

var Float64Array = require( '@stdlib/array/float64' );

// Create an array:
var out = new Float64Array( 10 );

// Fill the array with pseudorandom numbers:
randu( out.length, out, 1 );

The function has the following parameters:

N: number of indexed elements.
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, 0.0, 0.0, 0.0 ];

randu( 3, out, 2 );

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

var Float64Array = require( '@stdlib/array/float64' );

// Initial array:
var out0 = new Float64Array( 6 );

// Create offset views:
var out1 = new Float64Array( out0.buffer, out0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Fill the output array:
randu( out1.length, out1, 1 );

The function accepts the following options:

name: name of a supported pseudorandom number generator (PRNG), which will serve as the underlying source of pseudorandom numbers. The following generators are supported:
- mt19937: 32-bit Mersenne Twister.
- minstd: linear congruential pseudorandom number generator (LCG) based on Park and Miller.
- minstd-shuffle: linear congruential pseudorandom number generator (LCG) whose output is shuffled.
Default: 'mt19937'.
seed: pseudorandom number generator seed. Valid seed values vary according to the underlying PRNG.
state: pseudorandom number generator state. Valid state values vary according to the underlying PRNG. 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 a returned generator has exclusive control over its internal state. Default: true.

By default, the underlying pseudorandom number generator is mt19937. To use a different PRNG, set the name option.

var Float64Array = require( '@stdlib/array/float64' );

var opts = {
    'name': 'minstd-shuffle'
};

var out = new Float64Array( 10 );
randu( out.length, out, 1, opts );

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

var Float64Array = require( '@stdlib/array/float64' );

var opts = {
    'seed': 12345
};

var out = new Float64Array( 10 );
randu( out.length, out, 1, opts );

randu.ndarray( N, out, so, oo[, options] )

Fills a strided array with uniformly distributed pseudorandom numbers between 0 and 1 using alternative indexing semantics.

var Float64Array = require( '@stdlib/array/float64' );

// Create an array:
var out = new Float64Array( 10 );

// Fill the array with pseudorandom numbers:
randu.ndarray( out.length, out, 1, 0 );

The function has the following additional parameters:

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, 0.0, 0.0, 0.0 ];

randu.ndarray( 3, out, 2, 1 );

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

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 randu = require( '@stdlib/random/strided/randu' );

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

// Create an array:
var x1 = zeros( 10, 'float64' );

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

// Fill the array with pseudorandom numbers:
randu( x1.length, x1, 1, opts );

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

// Fill the array with the same pseudorandom numbers:
randu( x2.length, x2, 1, opts );

// Print the array contents:
logEach( 'x1[%d] = %.2f; x2[%d] = %.2f', idx, x1, idx, x2 );