npm install math-gammaGamma Function
===
[![NPM version][npm-image]][npm-url] [![Build Status][build-image]][build-url] [![Coverage Status][coverage-image]][coverage-url] [![Dependencies][dependencies-image]][dependencies-url]
> [Gamma][gamma-function] function.
The [gamma function][gamma-function] extends the [factorial function][factorial-function] to [real][real] and [complex][complex] numbers. If n is a positive integer,
Generalized to all complex numbers z, except for non-positive integers, the [gamma function][gamma-function] can be expressed as an infinite product
where γ ≈ 0.577216 is the [Euler–Mascheroni constant][euler-mascheroni-constant].
Installation
`` bash`
$ npm install math-gamma
Usage
` javascript`
var gamma = require( 'math-gamma' );
#### gamma( x )
Evaluates the [gamma function][gamma-function].
` javascript
var val = gamma( 4 );
// returns 3! = 6
val = gamma( -3/2 );
// returns ~2.363
val = gamma( -1/2 );
// returns ~-3.545
val = gamma( 1/2 );
// returns ~1.772
`
Examples
` javascript
var linspace = require( 'compute-linspace' );
var gamma = require( 'math-gamma' );
var x = linspace( -10, 10, 100 );
var v;
var i;
for ( i = 0; i < x.length; i++ ) {
v = gamma( x[ i ] );
console.log( 'x: %d, f(x): %d', x[ i ], v );
}
`
To run the example code from the top-level application directory,
` bash`
$ node ./examples/index.js
---
Tests
$3
This repository uses [tape][tape] for unit tests. To run the tests, execute the following command in the top-level application directory:
` bash`
$ make test
All new feature development should have corresponding unit tests to validate correct functionality.
$3
This repository uses [Istanbul][istanbul] as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:
` bash`
$ make test-cov
Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,
` bash`
$ make view-cov
$3
This repository uses [Testling][testling] for browser testing. To run the tests in a (headless) local web browser, execute the following command in the top-level application directory:
` bash`
$ make test-browsers
To view the tests in a local web browser,
` bash``
$ make view-browser-tests
---
License
Copyright
Copyright © 2016. The [Compute.io][compute-io] Authors.
[npm-image]: http://img.shields.io/npm/v/math-gamma.svg
[npm-url]: https://npmjs.org/package/math-gamma
[build-image]: http://img.shields.io/travis/math-io/gamma/master.svg
[build-url]: https://travis-ci.org/math-io/gamma
[coverage-image]: https://img.shields.io/codecov/c/github/math-io/gamma/master.svg
[coverage-url]: https://codecov.io/github/math-io/gamma?branch=master
[dependencies-image]: http://img.shields.io/david/math-io/gamma.svg
[dependencies-url]: https://david-dm.org/math-io/gamma
[dev-dependencies-image]: http://img.shields.io/david/dev/math-io/gamma.svg
[dev-dependencies-url]: https://david-dm.org/dev/math-io/gamma
[github-issues-image]: http://img.shields.io/github/issues/math-io/gamma.svg
[github-issues-url]: https://github.com/math-io/gamma/issues
[tape]: https://github.com/substack/tape
[istanbul]: https://github.com/gotwarlost/istanbul
[testling]: https://ci.testling.com
[compute-io]: https://github.com/compute-io/
[gamma-function]: https://en.wikipedia.org/wiki/Gamma_function
[factorial-function]: https://github.com/math-io/factorial
[real]: https://en.wikipedia.org/wiki/Real_number
[complex]: https://en.wikipedia.org/wiki/Complex_number
[euler-mascheroni-constant]: https://github.com/const-io/eulergamma