# @stdlib/math-base-special-gamma-lanczos-sum

0.1.0 • Public • Published
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# Gamma Lanczos Sum

Calculate the Lanczos sum for the approximation of the gamma function.

The Lanczos approximation for the gamma function can be written in partial fraction form as follows:

where `g` is an arbitrary constant and `L_g(n)` is the Lanczos sum.

## Installation

`npm install @stdlib/math-base-special-gamma-lanczos-sum`

## Usage

`var gammaLanczosSum = require( '@stdlib/math-base-special-gamma-lanczos-sum' );`

#### gammaLanczosSum( x )

Calculates the Lanczos sum for the approximation of the gamma function.

```var v = gammaLanczosSum( 4.0 );
// returns ~950.366

v = gammaLanczosSum( -1.5 );
// returns ~1373366.245

v = gammaLanczosSum( -0.5 );
// returns ~-699841.735

v = gammaLanczosSum( 0.5 );
// returns ~96074.186

v = gammaLanczosSum( 0.0 );
// returns Infinity

v = gammaLanczosSum( NaN );
// returns NaN```

## Examples

```var linspace = require( '@stdlib/array-base-linspace' );
var gammaLanczosSum = require( '@stdlib/math-base-special-gamma-lanczos-sum' );

var x = linspace( -10.0, 10.0, 100 );

var i;
for ( i = 0; i < x.length; i++ ) {
console.log( 'x: %d, f(x): %d', x[ i ], gammaLanczosSum( x[ i ] ) );
}```

## 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.

## License

See LICENSE.

Copyright © 2016-2023. The Stdlib Authors.

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