Package org.apache.commons.numbers.gamma

Class GammaRatio

java.lang.Object

org.apache.commons.numbers.gamma.GammaRatio

public final class GammaRatio
extends Object

Ratio of Gamma functions.

$$\frac{\mathrm{\Gamma }(a)}{\mathrm{\Gamma }(b)}$$

This code has been adapted from:

• The Boost c++ implementation <boost/math/special_functions/gamma.hpp>.

Since:

1.1

See Also:

Boost C++ Ratios of Gamma Functions

Method Summary

Modifier and Type	Method	Description
static double	delta(double a, double delta)	Computes the ratio of gamma functions of a value and an offset value.
static double	value(double a, double b)	Computes the ratio of gamma functions of two values.

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 a,
                           double b)

Computes the ratio of gamma functions of two values.

$$\frac{\mathrm{\Gamma }(a)}{\mathrm{\Gamma }(b)}$$

If either argument is <= 0 or infinite then the result is NaN.

Parameters:

a - Argument a (must be positive finite).

b - Argument b (must be positive finite).

Returns:

$\mathrm{\Gamma }(a)/\mathrm{\Gamma }(b)$

delta

public static double delta(double a,
                           double delta)

Computes the ratio of gamma functions of a value and an offset value.

$$\frac{\mathrm{\Gamma }(a)}{\mathrm{\Gamma }(a+delta)}$$

Note that the result is calculated accurately even when delta is small compared to a: indeed even if a+delta ~ a. The function is typically used when a is large and delta is very small.

Parameters:

a - Argument.

delta - Argument.

Returns:

$\mathrm{\Gamma }(a)/\mathrm{\Gamma }(a+delta)$