Creates a matrix or array filled with draws from a Lognormal distribution.
$ npm install distributions-lognormal-random
For use in the browser, use browserify.
var random = require( 'distributions-lognormal-random' );
Creates a matrix
or array
filled with draws from a Lognormal 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 a Lognormal distribution.
var out;
// Set seed
random.seed = 2;
out = random( 5 );
// returns [ ~0.435, ~2.085, ~0.239, ~1.059, ~0.878 ]
out = random( [2,1,2] );
// returns [ [ [~2.635,~0.674] ], [ [~1.821,~0.221] ] ]
The function accepts the following options
:
- mu: location parameter. Default:
0
. - sigma: scale parameter. 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
.
A Lognormal distribution is a function of two parameters: mu
(location parameter) and sigma
(scale parameter). By default, mu
is equal to 0
and sigma
is equal to 1
. To adjust either parameter, set the corresponding option.
var out = random( 5, {
'mu': 6,
'sigma': 4,
});
// returns [ ~80247.044, ~1218.376, ~1551.269, ~5268.923, ~112.821 ]
To be able to reproduce the generated random numbers, set the seed
option to a positive integer.
var out = random( 3, {
'seed': 22
});
// returns [ ~0.526, ~2.552, ~1.051 ]
var out = random( 3, {
'seed': 22
});
// returns [ ~0.526, ~2.552, ~1.051 ]
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 ~0.398
var out = random();
// returns ~1.476
random.seed = 11;
var out = random();
// returns ~0.398
var out = random();
// returns ~1.476
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( [~1.181,~2.499,~0.997,~0.923,~0.074] )
out = random( [3,2], {
'dtype': 'float64'
});
/*
[ ~0.618 ~1.315
~2.064 ~3.043
~1.837 ~2.857 ]
*/
Notes:
-
Currently, for more than
2
dimensions, the function outputs a genericarray
and ignores any specifieddtype
.var out = random( [2,1,3], { 'dtype': 'float32' }); // returns [ [ [~2.395,~0.600,~0.690] ], [ [~1.482,~0.792,~2.476] ] ]
var random = require( 'distributions-lognormal-random' ),
out;
// Set seed
random.seed = 4;
// 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
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.
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
Copyright © 2015. The Compute.io Authors.