@stdlib/stats-base-dists-discrete-uniform-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 discrete uniform distribution.

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

    Probability mass function (PMF) for a discrete uniform distribution.

    where a is the minimum support and b is the maximum support of the distribution. The parameters must satisfy a <= b.

    Installation

    npm install @stdlib/stats-base-dists-discrete-uniform-logpmf

    Usage

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

    logpmf( x, a, b )

    Evaluates the natural logarithm of the probability mass function (PMF) for a discrete uniform distribution with parameters a (minimum support) and b (maximum support).

    var y = logpmf( 2.0, 0, 4 );
    // returns ~-1.609
    
    y = logpmf( 5.0, 0, 4 );
    // returns -Infinity
    
    y = logpmf( 3, -4, 4 );
    // returns ~-2.197

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

    var y = logpmf( NaN, -2, 2 );
    // returns NaN
    
    y = logpmf( 1.0, NaN, 4 );
    // returns NaN
    
    y = logpmf( 2.0, 0, NaN );
    // returns NaN

    If a or b is not an integer value, the function returns NaN.

    var y = logpmf( 2.0, 1, 5.5 );
    // returns NaN

    If provided a > b, the function returns NaN.

    var y = logpmf( 2.0, 3, 2 );
    // returns NaN

    logpmf.factory( a, b )

    Returns a function for evaluating the PMF for a discrete uniform distribution with parameters a (minimum support) and b (maximum support).

    var myLogPMF = logpmf.factory( 6, 7 );
    var y = myLogPMF( 7.0 );
    // returns ~-0.693
    
    y = myLogPMF( 5.0 );
    // returns -Infinity

    Examples

    var randint = require( '@stdlib/random-base-discrete-uniform' );
    var logpmf = require( '@stdlib/stats-base-dists-discrete-uniform-logpmf' );
    
    var randa = randint.factory( 0, 10 );
    var randb = randint.factory();
    var a;
    var b;
    var x;
    var y;
    var i;
    
    for ( i = 0; i < 25; i++ ) {
        a = randa();
        x = randb( a, a+randa() );
        b = randb( a, a+randa() );
        y = logpmf( x, a, b );
        console.log( 'x: %d, a: %d, b: %d, ln(P(X=x;a,b)): %d', x.toFixed( 4 ), a.toFixed( 4 ), b.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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    Copyright

    Copyright © 2016-2022. The Stdlib Authors.

    Install

    npm i @stdlib/stats-base-dists-discrete-uniform-logpmf

    Homepage

    stdlib.io

    DownloadsWeekly Downloads

    88

    Version

    0.0.7

    License

    Apache-2.0

    Unpacked Size

    50.3 kB

    Total Files

    11

    Last publish

    Collaborators

    • stdlib-bot
    • kgryte
    • planeshifter
    • rreusser