Uniform Random Variables

Creates a matrix or array filled with draws from a uniform distribution.

Installation

$ npm install distributions-uniform-random

For use in the browser, use browserify.

Usage

var random = require( 'distributions-uniform-random' );

random( [dims][, opts] )

Creates a matrix or array filled with draws from an uniform distribution. The dims argument may either be a positive integer specifying a length or an array of positive integers specifying dimensions. If no dims argument is supplied,the function returns a single random draw from an uniform distribution.

var out;

// Set seed
random.seed = 2;

out = random( 5 );
// returns [ ~0.243, ~0.277, ~0.894, ~0.332, ~0.133 ]

out = random( [2,1,2] );
// returns [ [ [~0.431,~0.578] ], [~0.123,~0.391] ] ]

The function accepts the following options:

• a: minimum support. Default: 0.
• b: maximum support. Default: 1.
• seed: positive integer used as a seed to initialize the generator. If not supplied, uniformly distributed random numbers are generated via an underlying generator seedable by setting the seed property of the exported function.
• dtype: output data type (see matrix for a list of acceptable data types). Default: generic.

The continuous uniform distribution is a function of two parameters: a(minimum support) and b(maximum support). It is required that a < b. By default, a is equal to 0 and b is equal to one. To adjust either parameter, set the corresponding option.

var out = random( 5, {
	'a': 10,
	'b': 20
});
// returns [ ~19.403, ~12.457, 10.78, ~11.304, ~14.655 ]

To be able to reproduce the generated random variates, set the seed option to a positive integer.

var out = random( 3, {
	'seed': 22
});
// returns [ ~0.243, ~0.855, ~0.962 ]

var out = random( 3, {
    'seed': 22
});
// returns [ ~0.243, ~0.855, ~0.962 ]

If no seed option is supplied, each function call uses a common underlying uniform number generator. A positive-integer seed for this underlying generator can be supplied by setting the seed property of the exported function.

random.seed = 11;
var out = random();
// returns ~0.243

var out = random();
// returns 0.46

random.seed = 11;
var out = random();
// returns ~0.243

var out = random();
// returns 0.46

By default, the output data structure is a generic array. To output a typed array or matrix, set the dtype option.

var out;

out = random( 5, {
	'dtype': 'float32'
});
// returns Float32Array( [~0.859,~0.421,~0.013,~0.118,0.2] )

out = random( [3,2], {
	'dtype': 'float64'
});
/*
	[ ~0.916 ~0.091
	  ~0.231 ~0.463
	  ~0.773 0.5 ]
*/

Notes:

• Currently, for more than 2 dimensions, the function outputs a generic array and ignores any specified dtype.

  var out = random( [2,1,3], {
  	'dtype': 'float32'
  });
  // returns [ [ [~0.866,~0.851,~0.941] ],[ [ ~0.499,~0.294,~0.468 ] ] ]

Examples

var random = require( 'distributions-uniform-random' ),
	out;

// Set seed
random.seed = 23;

// Plain arrays...

// 1x10:
out = random( 10 );

// 2x1x3:
out = random( [2,1,3] );

// 5x5x5:
out = random( [5,5,5] );

// 10x5x10x20:
out = random( [10,5,10,20] );

// Typed arrays...
out = random( 10, {
	'dtype': 'float32'
});

// Matrices...
out = random( [3,2], {
	'dtype': 'float64'
});

To run the example code from the top-level application directory,

$ node ./examples/index.js

Tests

Unit

Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:

$ make test

All new feature development should have corresponding unit tests to validate correct functionality.

Test Coverage

This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:

$ make test-cov

Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,

$ make view-cov

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License

MIT license.

Copyright

Copyright © 2015. The Compute.io Authors.