README.md

About stdlib...

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Skewness

Erlang distribution skewness.

The skewness for an Erlang random variable with shape k and rate λ is

$$\mathop{\mathrm{skew}}\left( X \right) = \frac{2}{\sqrt{k}}$$

Usage

import skewness from 'https://cdn.jsdelivr.net/gh/stdlib-js/stats-base-dists-erlang-skewness@deno/mod.js';

skewness( k, lambda )

Returns the skewness of an Erlang distribution with parameters k (shape parameter) and lambda (rate parameter).

var v = skewness( 1, 1.0 );
// returns 2.0

v = skewness( 4, 12.0 );
// returns 1.0

v = skewness( 8, 2.0 );
// returns ~0.707

If provided NaN as any argument, the function returns NaN.

var v = skewness( NaN, 2.0 );
// returns NaN

v = skewness( 2.0, NaN );
// returns NaN

If not provided a positive integer for k, the function returns NaN.

var v = skewness( 1.8, 1.0 );
// returns NaN

v = skewness( -1.0, 1.0 );
// returns NaN

If provided lambda <= 0, the function returns NaN.

var v = skewness( 2, 0.0 );
// returns NaN

v = skewness( 2, -1.0 );
// returns NaN

Examples

import randu from 'https://cdn.jsdelivr.net/gh/stdlib-js/random-base-randu@deno/mod.js';
import round from 'https://cdn.jsdelivr.net/gh/stdlib-js/math-base-special-round@deno/mod.js';
import EPS from 'https://cdn.jsdelivr.net/gh/stdlib-js/constants-float64-eps@deno/mod.js';
import skewness from 'https://cdn.jsdelivr.net/gh/stdlib-js/stats-base-dists-erlang-skewness@deno/mod.js';

var lambda;
var k;
var v;
var i;

for ( i = 0; i < 10; i++ ) {
    k = round( randu()*10.0 );
    lambda = ( randu()*10.0 ) + EPS;
    v = skewness( k, lambda );
    console.log( 'k: %d, λ: %d, skew(X;k,λ): %d', k.toFixed( 4 ), lambda.toFixed( 4 ), v.toFixed( 4 ) );
}

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Notice

This package is part of stdlib, a standard library with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

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

Copyright © 2016-2024. The Stdlib Authors.