@stdlib/stats-base-dists-gamma-mean
v0.3.1TypeScript
Gamma distribution expected value.
0/weekUpdated 1 weeks agoApache-2.0Unpacked: 39.7 KB
Published by The Stdlib Authors
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About stdlib...
Mean
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> [Gamma][gamma-distribution] distribution [expected value][expected-value].
The [expected value][expected-value] for a [gamma][gamma-distribution] random variable is
where α > 0 is the shape parameter β > 0 is the rate parameter.
Installation
``bash`
npm install @stdlib/stats-base-dists-gamma-mean
Usage
`javascript`
var mean = require( '@stdlib/stats-base-dists-gamma-mean' );
#### mean( alpha, beta )
Returns the [expected value][expected-value] of a [gamma][gamma-distribution] distribution with parameters alpha (shape parameter) and beta (rate parameter).
`javascript
var v = mean( 1.0, 1.0 );
// returns 1.0
v = mean( 4.0, 12.0 );
// returns ~0.333
v = mean( 8.0, 2.0 );
// returns 4.0
`
If provided NaN as any argument, the function returns NaN.
`javascript
var v = mean( NaN, 2.0 );
// returns NaN
v = mean( 2.0, NaN );
// returns NaN
`
If provided alpha <= 0, the function returns NaN.
`javascript
var v = mean( 0.0, 1.0 );
// returns NaN
v = mean( -1.0, 1.0 );
// returns NaN
`
If provided beta <= 0, the function returns NaN.
`javascript
var v = mean( 1.0, 0.0 );
// returns NaN
v = mean( 1.0, -1.0 );
// returns NaN
`
Examples
`javascript
var uniform = require( '@stdlib/random-array-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var EPS = require( '@stdlib/constants-float64-eps' );
var mean = require( '@stdlib/stats-base-dists-gamma-mean' );
var opts = {
'dtype': 'float64'
};
var alpha = uniform( 10, EPS, 10.0, opts );
var beta = uniform( 10, EPS, 10.0, opts );
logEachMap( 'α: %0.4f, β: %0.4f, E(X;α,β): %0.4f', alpha, beta, mean );
`
*
C APIs
$3
`c`
#include "stdlib/stats/base/dists/gamma/mean.h"
#### stdlib_base_dists_gamma_mean( alpha, beta )
Returns the [expected value][expected-value] of a [gamma][gamma-distribution] distribution with parameters alpha (shape parameter) and beta (rate parameter).
`c`
double out = stdlib_base_dists_gamma_mean( 1.0, 1.0 );
// returns 1.0
The function accepts the following arguments:
- alpha: [in] double shape parameter.[in] double
- beta: rate parameter.
`c`
double stdlib_base_dists_gamma_mean( const double alpha, const double beta );
$3
`c
#include "stdlib/stats/base/dists/gamma/mean.h"
#include
#include
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 beta;
double y;
int i;
for ( i = 0; i < 25; i++ ) {
alpha = random_uniform( 0.0, 20.0 );
beta = random_uniform( 0.0, 20.0 );
y = stdlib_base_dists_gamma_mean( alpha, beta );
printf( "α: %lf, β: %lf, E(X;α,β): %lf\n", alpha, beta, y );
}
}
`
*
Notice
This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].
#### Community
[![Chat][chat-image]][chat-url]
---
License
See [LICENSE][stdlib-license].
Copyright
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules
[deno-url]: https://github.com/stdlib-js/stats-base-dists-gamma-mean/tree/deno
[deno-readme]: https://github.com/stdlib-js/stats-base-dists-gamma-mean/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/stats-base-dists-gamma-mean/tree/umd
[umd-readme]: https://github.com/stdlib-js/stats-base-dists-gamma-mean/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/stats-base-dists-gamma-mean/tree/esm
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[branches-url]: https://github.com/stdlib-js/stats-base-dists-gamma-mean/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/stats-base-dists-gamma-mean/main/LICENSE
[gamma-distribution]: https://en.wikipedia.org/wiki/Gamma_distribution
[expected-value]: https://en.wikipedia.org/wiki/Expected_value