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    @stdlib/stats-base-dists-weibull-variance
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    0.0.7 • Public • Published

    Variance

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    Weibull distribution variance.

    The variance for a Weibull random variable is

    Variance for a Weibull distribution.

    where λ > 0 is the shape parameter, k > 0 is the scale parameter, and Γ denotes the gamma function.

    Installation

    npm install @stdlib/stats-base-dists-weibull-variance

    Usage

    var variance = require( '@stdlib/stats-base-dists-weibull-variance' );

    variance( k, lambda )

    Returns the variance of a Weibull distribution with parameters k (shape parameter) and lambda (scale parameter).

    var v = variance( 1.0, 1.0 );
    // returns 1.0
    
    v = variance( 4.0, 12.0 );
    // returns ~9.311
    
    v = variance( 8.0, 2.0 );
    // returns ~0.078

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

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

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

    var v = variance( 0.0, 1.0 );
    // returns NaN
    
    v = variance( -1.0, 1.0 );
    // returns NaN

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

    var v = variance( 1.0, 0.0 );
    // returns NaN
    
    v = variance( 1.0, -1.0 );
    // returns NaN

    Examples

    var randu = require( '@stdlib/random-base-randu' );
    var EPS = require( '@stdlib/constants-float64-eps' );
    var variance = require( '@stdlib/stats-base-dists-weibull-variance' );
    
    var lambda;
    var k;
    var v;
    var i;
    
    for ( i = 0; i < 10; i++ ) {
        k = ( randu()*10.0 ) + EPS;
        lambda = ( randu()*10.0 ) + EPS;
        v = variance( k, lambda );
        console.log( 'k: %d, λ: %d, Var(X;k,λ): %d', k.toFixed( 4 ), lambda.toFixed( 4 ), v.toFixed( 4 ) );
    }

    Notice

    This package is part of stdlib, a standard library for JavaScript and Node.js, 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.

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    License

    See LICENSE.

    Copyright

    Copyright © 2016-2022. The Stdlib Authors.

    Install

    npm i @stdlib/stats-base-dists-weibull-variance

    Homepage

    stdlib.io

    DownloadsWeekly Downloads

    107

    Version

    0.0.7

    License

    Apache-2.0

    Unpacked Size

    36.5 kB

    Total Files

    10

    Last publish

    Collaborators

    • stdlib-bot
    • kgryte
    • planeshifter
    • rreusser