README.md

Mean

Rayleigh distribution expected value.

The expected value for a Rayleigh random variable is

$$\mathbb{E}\left[ X \right] = \sigma \sqrt{\dfrac{\pi}{2}}$$

where σ > 0 is the scale parameter.

Usage

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

mean( sigma )

Returns the expected value of a Rayleigh distribution with scale parameter sigma.

var y = mean( 9.0 );
// returns ~11.28

y = mean( 1.5 );
// returns ~1.88

If provided sigma < 0, the function returns NaN.

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

y = mean( -0.1 );
// returns NaN

Examples

var uniform = require( '@stdlib/random/array/uniform' );
var logEachMap = require( '@stdlib/console/log-each-map' );
var mean = require( '@stdlib/stats/base/dists/rayleigh/mean' );

var opts = {
    'dtype': 'float64'
};
var sigma = uniform( 10, 0.0, 20.0, opts );

logEachMap( 'σ: %0.4f, E(X;σ): %0.4f', sigma, mean );

---

C APIs

Usage

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

stdlib_base_dists_rayleigh_mean( sigma )

Returns the mean of a Rayleigh distribution.

double out = stdlib_base_dists_rayleigh_mean( 9.0 );
// returns ~11.28

The function accepts the following arguments:

• sigma: [in] double scale parameter.

double stdlib_base_dists_rayleigh_mean( const double sigma );

Examples

#include "stdlib/stats/base/dists/rayleigh/mean.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 sigma;
    double y;
    int i;

    for ( i = 0; i < 25; i++ ) {
        sigma = random_uniform( 0.0, 20.0 );
        y = stdlib_base_dists_rayleigh_mean( sigma );
        printf( "σ: %lf, E(X;σ): %lf\n", sigma, y );
    }
}