gamma1pm1

Compute gamma(x+1) - 1.

Usage

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.

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

Examples

var randu = require( '@stdlib/random/base/randu' );
var gamma1pm1 = require( '@stdlib/math/base/special/gamma1pm1' );

var x;
var i;

for ( i = 0; i < 100; i++ ) {
    x = (randu()*10.0) - 5.0;
    console.log( 'gamma(%d+1) - 1 = %d', x, gamma1pm1( x ) );
}

C APIs

Usage

#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.

double out = stdlib_base_gamma1pm1( 0.2 );
// returns ~-0.082

The function accepts the following arguments:

x: [in] double input value.

double stdlib_base_gamma1pm1( const double x );

Examples

#include "stdlib/math/base/special/gamma1pm1.h"
#include <stdio.h>

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 );
    }
}