Compute gamma(x+1) - 1.
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> Compute gamma(x+1) - 1.
``bash`
npm install @stdlib/math-base-special-gamma1pm1
`javascript`
var gamma1pm1 = require( '@stdlib/math-base-special-gamma1pm1' );
#### gamma1pm1( x )
Computes gamma(x+1) - 1 without cancellation errors for small x and where gamma(x) is the [gamma function][@stdlib/math/base/special/gamma].
`javascript
var v = gamma1pm1( 0.2 );
// returns ~-0.082
v = gamma1pm1( -8.5 );
// returns ~-1.0
v = gamma1pm1( 0.0 );
// returns 0.0
v = gamma1pm1( NaN );
// returns NaN
`
`javascript
var uniform = require( '@stdlib/random-array-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var gamma1pm1 = require( '@stdlib/math-base-special-gamma1pm1' );
var opts = {
'dtype': 'float64'
};
var x = uniform( 100, -5.0, 5.0, opts );
logEachMap( 'gamma(%0.4f+1) - 1 = %0.4f', x, gamma1pm1 );
`
*
`c`
#include "stdlib/math/base/special/gamma1pm1.h"
#### stdlib_base_gamma1pm1( x )
Computes gamma(x+1) - 1 without cancellation errors for small x and where gamma(x) is the [gamma function][@stdlib/math/base/special/gamma].
`c`
double out = stdlib_base_gamma1pm1( 0.2 );
// returns ~-0.082
The function accepts the following arguments:
- x: [in] double input value.
`c`
double stdlib_base_gamma1pm1( const double x );
`c
#include "stdlib/math/base/special/gamma1pm1.h"
#include
int main( void ) {
const double x[] = { 4.0, -1.5, -0.5, 0.5 };
double y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_gamma1pm1( x[ i ] );
printf( "gamma1pm1(%lf) = %lf\n", x[ i ], y );
}
}
`
*
- [@stdlib/math-base/special/gamma][@stdlib/math/base/special/gamma]: gamma function.
- [@stdlib/math-base/special/gammainc][@stdlib/math/base/special/gammainc]: incomplete gamma function.
- [@stdlib/math-base/special/gammaincinv][@stdlib/math/base/special/gammaincinv]: inverse incomplete gamma function.
- [@stdlib/math-base/special/gammaln][@stdlib/math/base/special/gammaln]: natural logarithm of the gamma function.
*
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].
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