Mean

Lognormal distribution expected value.

The mean for a lognormal random variable is

where μ is the location parameter and σ > 0 is the scale parameter. According to the definition, the natural logarithm of a random variable from a lognormal distribution follows a normal distribution.

Installation

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

Usage

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

mean( mu, sigma )

Returns the expected value for a lognormal distribution with location mu and scale sigma.

var y = mean( 2.0, 1.0 );
// returns ~12.182

y = mean( 0.0, 1.0 );
// returns ~1.649

y = mean( -1.0, 4.0 );
// returns ~1096.633

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

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

y = mean( 0.0, NaN );
// returns NaN

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

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

y = mean( 0.0, -1.0 );
// 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-lognormal-mean' );

var opts = {
    'dtype': 'float64'
};
var mu = uniform( 10, -5.0, 5.0, opts );
var sigma = uniform( 10, 0.0, 20.0, opts );

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

C APIs

Usage

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

stdlib_base_dists_lognormal_mean( mu, sigma )

Returns the expected value for a lognormal distribution with location mu and scale sigma.

double out = stdlib_base_dists_lognormal_mean( 0.0, 1.0 );
// returns ~1.649

The function accepts the following arguments:

• mu: [in] double location parameter.
• sigma: [in] double scale parameter.

double stdlib_base_dists_lognormal_mean( const double mu, const double sigma );

Examples

#include "stdlib/stats/base/dists/lognormal/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 mu;
    double y;
    int i;

    for ( i = 0; i < 10; i++ ) {
        mu = random_uniform( -5.0, 5.0 );
        sigma = random_uniform( 0.1, 20.0 );
        y = stdlib_base_dists_lognormal_mean( mu, sigma );
        printf( "µ: %.4f, σ: %.4f, E(X;µ,σ): %.4f\n", mu, 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.