Package org.apache.commons.numbers.gamma

Class LogGamma

java.lang.Object

org.apache.commons.numbers.gamma.LogGamma

public final class LogGamma
extends Object

Natural logarithm of the absolute value of $\mathrm{\Gamma }(x)$.

$$\mathrm{lgamma}(z)=\ln |\mathrm{\Gamma }(x)|$$

This code has been adapted from the Boost c++ implementation <boost/math/special_functions/gamma.hpp>.

See Also:

Boost C++ Log Gamma functions

Method Summary

Modifier and Type	Method	Description
static double	value(double x)	Computes the function $\ln |\mathrm{\Gamma }(x)|$, the natural logarithm of the absolute value of $\mathrm{\Gamma }(x)$.
static double	value(double x, int[] sign)	Computes the function $\ln |\mathrm{\Gamma }(x)|$, the natural logarithm of the absolute value of $\mathrm{\Gamma }(x)$.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

value

public static double value(double x)

Computes the function $\ln |\mathrm{\Gamma }(x)|$, the natural logarithm of the absolute value of $\mathrm{\Gamma }(x)$.

Parameters:

x - Argument.

Returns:

$\ln |\mathrm{\Gamma }(x)|$, or NaN if x <= 0 and is an integer.

value

public static double value(double x,
                           int[] sign)

Computes the function $\ln |\mathrm{\Gamma }(x)|$, the natural logarithm of the absolute value of $\mathrm{\Gamma }(x)$.

The sign output is set to 1 if the sign of gamma(x) is positive or zero; otherwise it is set to -1.

Parameters:

x - Argument.

sign - Sign output. If a non-zero length the first index sign[0] is set on output to the sign of gamma(z).

Returns:

$\ln |\mathrm{\Gamma }(x)|$, or NaN if x <= 0 and is an integer.

Since:

1.1