Mean

Rayleigh distribution expected value.

The expected value for a Rayleigh random variable is

double-struck upper E left-bracket upper X right-bracket equals sigma StartRoot StartFraction pi Over 2 EndFraction EndRoot

where σ > 0 is the scale parameter.

Usage

var mean = require( '@stdlib/math/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 randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var mean = require( '@stdlib/math/base/dists/rayleigh/mean' );

var sigma;
var y;
var i;

for ( i = 0; i < 10; i++ ) {
    sigma = randu() * 20.0;
    y = mean( sigma );
    console.log( 'σ: %d, E(X,σ): %d', sigma.toFixed( 4 ), y.toFixed( 4 ) );
}