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Median

Exponential distribution median.

The median for an exponential random variable is

$$\mathop{\mathrm{Median}}\left( X \right) = \lambda^{−1} \ln(2)$$

where λ is the rate parameter.

Installation

npm install @stdlib/stats-base-dists-exponential-median

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

var median = require( '@stdlib/stats-base-dists-exponential-median' );

median( lambda )

Returns the median of a exponential distribution with rate parameter lambda.

var v = median( 9.0 );
// returns ~0.077

v = median( 0.5 );
// returns ~1.386

If provided lambda < 0, the function returns NaN.

var v = median( -1.0 );
// returns NaN

Examples

var randu = require( '@stdlib/random-base-randu' );
var round = require( '@stdlib/math-base-special-round' );
var median = require( '@stdlib/stats-base-dists-exponential-median' );

var lambda;
var v;
var i;

for ( i = 0; i < 10; i++ ) {
    lambda = randu() * 20.0;
    v = median( lambda );
    console.log( 'λ: %d, Median(X;λ): %d', lambda.toFixed( 4 ), v.toFixed( 4 ) );
}

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C APIs

Usage

#include "stdlib/stats/base/dists/exponential/median.h"

stdlib_base_dists_exponential_median( lambda )

Returns the median of an exponential distribution.

double out = stdlib_base_dists_exponential_median( 9.0 );
// returns ~0.077

The function accepts the following arguments:

• lambda: [in] double rate parameter.

double stdlib_base_dists_exponential_median( const double lambda );

Examples

#include "stdlib/stats/base/dists/exponential/median.h"
#include <stdlib.h>
#include <stdio.h>

static double random_uniform( const double min, const double max ) {
    double v = (double)rand() / ( (double)RAND_MAX + 1.0 );
    return min + ( v*(max-min) );
}

int main( void ) {
    double lambda;
    double y;
    int i;

    for ( i = 0; i < 25; i++ ) {
        lambda = random_uniform( 0.0, 20.0 );
        y = stdlib_base_dists_exponential_median( lambda );
        printf( "λ: %lf, Median(X;λ): %lf\n", lambda, y );
    }
}

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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.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.