Standard Deviation

Half-normal distribution standard deviation.

The standard deviation for a half-normal random variable is

where σ > 0 is the scale parameter.

Installation

npm install @stdlib/stats-base-dists-halfnormal-stdev

Usage

var stdev = require( '@stdlib/stats-base-dists-halfnormal-stdev' );

stdev( sigma )

Returns the standard deviation of a half-normal distribution with scale sigma.

var y = stdev( 9.0 );
// returns ~5.425

y = stdev( 3.5 );
// returns ~2.1098

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

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

Examples

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

var opts = {
    'dtype': 'float64'
};
var sigma = uniform( 10, 0.1, 20.0, opts );

logEachMap( 'σ: %0.4f, SD(X;σ): %0.4f', sigma, stdev );

C APIs

Usage

#include "stdlib/stats/base/dists/halfnormal/stdev.h"

stdlib_base_dists_halfnormal_stdev( sigma )

Returns the standard deviation of a half-normal distribution with scale sigma.

double out = stdlib_base_dists_halfnormal_stdev( 9.0 ); 
// returns ~5.425

The function accepts the following arguments:

• sigma: [in] double scale parameter.

double stdlib_base_dists_halfnormal_stdev( const double sigma );

Examples

#include "stdlib/stats/base/dists/halfnormal/stdev.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( 0.1, 20.0 );
        y = stdlib_base_dists_halfnormal_stdev( sigma );
        printf( "σ: %lf, SD(X;σ): %lf\n", sigma, 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.