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    @stdlib/stats-base-dists-binomial-logpmf
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    0.0.7 • Public • Published

    Logarithm of Probability Mass Function

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    Evaluate the natural logarithm of the probability mass function (PMF) for a binomial distribution.

    The probability mass function (PMF) for a binomial random variable is

    Probability mass function (PMF) for a binomial distribution.

    where n is the number of trials and 0 <= p <= 1 is the success probability.

    Installation

    npm install @stdlib/stats-base-dists-binomial-logpmf

    Usage

    var logpmf = require( '@stdlib/stats-base-dists-binomial-logpmf' );

    logpmf( x, n, p )

    Evaluates the natural logarithm of the probability mass function (PMF) for a binomial distribution with number of trials n and success probability p.

    var y = logpmf( 3.0, 20, 0.2 );
    // returns ~-1.583
    
    y = logpmf( 21.0, 20, 0.2 );
    // returns -Infinity
    
    y = logpmf( 5.0, 10, 0.4 );
    // returns ~-1.606
    
    y = logpmf( 0.0, 10, 0.4 );
    // returns ~-5.108

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

    var y = logpmf( NaN, 20, 0.5 );
    // returns NaN
    
    y = logpmf( 0.0, NaN, 0.5 );
    // returns NaN
    
    y = logpmf( 0.0, 20, NaN );
    // returns NaN

    If provided a number of trials n which is not a nonnegative integer, the function returns NaN.

    var y = logpmf( 2.0, 1.5, 0.5 );
    // returns NaN
    
    y = logpmf( 2.0, -2.0, 0.5 );
    // returns NaN

    If provided a success probability p outside of [0,1], the function returns NaN.

    var y = logpmf( 2.0, 20, -1.0 );
    // returns NaN
    
    y = logpmf( 2.0, 20, 1.5 );
    // returns NaN

    logpmf.factory( n, p )

    Returns a function for evaluating the probability mass function (PMF) of a binomial distribution with number of trials n and success probability p.

    var mylogpmf = logpmf.factory( 10, 0.5 );
    
    var y = mylogpmf( 3.0 );
    // returns ~-2.144
    
    y = mylogpmf( 5.0 );
    // returns ~-1.402

    Examples

    var randu = require( '@stdlib/random-base-randu' );
    var round = require( '@stdlib/math-base-special-round' );
    var logpmf = require( '@stdlib/stats-base-dists-binomial-logpmf' );
    
    var i;
    var n;
    var p;
    var x;
    var y;
    
    for ( i = 0; i < 10; i++ ) {
        x = round( randu() * 20.0 );
        n = round( randu() * 100.0 );
        p = randu();
        y = logpmf( x, n, p );
        console.log( 'x: %d, n: %d, p: %d, ln(P(X = x;n,p)): %d', x, n, p.toFixed( 4 ), y.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-binomial-logpmf

    Homepage

    stdlib.io

    DownloadsWeekly Downloads

    77

    Version

    0.0.7

    License

    Apache-2.0

    Unpacked Size

    54.9 kB

    Total Files

    11

    Last publish

    Collaborators

    • stdlib-bot
    • kgryte
    • planeshifter
    • rreusser