Mean

Fréchet distribution expected value.

The expected value for a Fréchet random variable shape α > 0, scale s > 0, and location parameter m is

where Γ is the gamma function.

Installation

npm install @stdlib/stats-base-dists-frechet-mean

Usage

var mean = require( '@stdlib/stats-base-dists-frechet-mean' );

mean( alpha, s, m )

Returns the expected value for a Fréchet distribution with shape alpha > 0, scale s > 0, and location parameter m.

var y = mean( 2.0, 1.0, 1.0 );
// returns ~2.772

y = mean( 4.0, 4.0, -1.0 );
// returns ~3.902

y = mean( 1.0, 1.0, 2.0 );
// returns Infinity

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

var y = mean( NaN, 1.0, -2.0 );
// returns NaN

y = mean( 1.0, NaN, -2.0 );
// returns NaN

y = mean( 1.0, 1.0, NaN );
// returns NaN

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

var y = mean( 0.0, 3.0, 2.0 );
// returns NaN

y = mean( 0.0, -1.0, 2.0 );
// returns NaN

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

var y = mean( 1.0, 0.0, 2.0 );
// returns NaN

y = mean( 1.0, -1.0, 2.0 );
// returns NaN

Examples

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

var alpha;
var m;
var s;
var y;
var i;

for ( i = 0; i < 10; i++ ) {
    alpha = ( randu()*20.0 ) + EPS;
    s = ( randu()*20.0 ) + EPS;
    m = ( randu()*40.0 ) - 20.0;
    y = mean( alpha, s, m );
    console.log( 'α: %d, s: %d, m: %d, E(X;α,s,m): %d', alpha.toFixed( 4 ), s.toFixed( 4 ), m.toFixed( 4 ), y.toFixed( 4 ) );
}

C APIs

Usage

#include "stdlib/stats/base/dists/frechet/mean.h"

stdlib_base_dists_frechet_mean( alpha, s, m )

Evaluates the expected value for a Fréchet distribution with shape alpha > 0, scale s > 0, and location parameter m.

double out = stdlib_base_dists_frechet_mean( 5.0, 2.0, 0.0 );
// returns ~2.328

The function accepts the following arguments:

• alpha: [in] double shape parameter.
• s: [in] double scale parameter.
• m: [in] double location parameter.

double stdlib_base_dists_frechet_mean( const double alpha, const double s, const double m );

Examples

#include "stdlib/stats/base/dists/frechet/mean.h"
#include "stdlib/constants/float64/eps.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 alpha;
    double s;
    double m;
    double y;
    int i;

    for ( i = 0; i < 25; i++ ) {
        alpha = random_uniform( STDLIB_CONSTANT_FLOAT64_EPS, 20.0 );
        s = random_uniform( STDLIB_CONSTANT_FLOAT64_EPS, 20.0 );
        m = random_uniform( -20.0, 20.0 );
        y = stdlib_base_dists_frechet_mean( alpha, s, m );
        printf( "α: %lf, s: %lf, m: %lf, E(X;α,s,m): %lf\n", alpha, s, m, y );
    }
}

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

License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.