@stdlib/stats-base-dists-betaprime-quantile NPM

Quantile Function

Beta prime distribution quantile function.

The quantile function for a beta prime random variable with first shape parameter α > 0 and second shape parameter β > 0 is

for 0 <= p <= 1, where G^-1 denotes the quantile function of a beta random variable with parameters α and β.

Installation

npm install @stdlib/stats-base-dists-betaprime-quantile

Usage

var quantile = require( '@stdlib/stats-base-dists-betaprime-quantile' );

quantile( p, alpha, beta )

Evaluates the quantile function for a beta prime distribution with parameters alpha (first shape parameter) and beta (second shape parameter).

var y = quantile( 0.8, 2.0, 1.0 );
// returns ~8.472

y = quantile( 0.5, 4.0, 2.0 );
// returns ~2.187

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

var y = quantile( 1.9, 1.0, 1.0 );
// returns NaN

y = quantile( -0.1, 1.0, 1.0 );
// returns NaN

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

var y = quantile( NaN, 1.0, 1.0 );
// returns NaN

y = quantile( 0.5, NaN, 1.0 );
// returns NaN

y = quantile( 0.5, 1.0, NaN );
// returns NaN

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

var y = quantile( 0.4, -1.0, 1.0 );
// returns NaN

y = quantile( 0.4, 0.0, 1.0 );
// returns NaN

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

var y = quantile( 0.4, 1.0, -1.0 );
// returns NaN

y = quantile( 0.4, 1.0, 0.0 );
// returns NaN

quantile.factory( alpha, beta )

Returns a function for evaluating the quantile function of a beta prime distribution with parameters alpha (first shape parameter) and beta (second shape parameter).

var myQuantile = quantile.factory( 2.0, 2.0 );

var y = myQuantile( 0.8 );
// returns ~2.483

y = myQuantile( 0.4 );
// returns ~0.763

Examples

var randu = require( '@stdlib/random-base-randu' );
var EPS = require( '@stdlib/constants-float64-eps' );
var quantile = require( '@stdlib/stats-base-dists-betaprime-quantile' );

var alpha;
var beta;
var p;
var y;
var i;

for ( i = 0; i < 10; i++ ) {
    p = randu();
    alpha = ( randu()*5.0 ) + EPS;
    beta = ( randu()*5.0 ) + EPS;
    y = quantile( p, alpha, beta );
    console.log( 'p: %d, α: %d, β: %d, Q(p;α,β): %d', p.toFixed( 4 ), alpha.toFixed( 4 ), beta.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.