com.numericalmethod.suanshu.analysis.function.special.gamma

Class GammaLanczos

java.lang.Object

com.numericalmethod.suanshu.analysis.function.rn2r1.univariate.UnivariateRealFunction

com.numericalmethod.suanshu.analysis.function.special.gamma.GammaLanczos

All Implemented Interfaces:

Function<Vector,java.lang.Double>, RealScalarFunction, Gamma, java.io.Serializable

public class GammaLanczos
extends UnivariateRealFunction
implements Gamma

Lanczos approximation provides a way to compute the Gamma function such that the accuracy can be made arbitrarily precise. Yet, the computations can be time-consuming if done in, e.g., BigDecimal.

See Also:

Wikipedia: Lanczos approximation, Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface com.numericalmethod.suanshu.analysis.function.Function

Function.EvaluationException

Constructor Summary

Constructors

Constructor and Description
GammaLanczos() Construct an instance of a Gamma function, computed using the Lanczos approximation.
GammaLanczos(double g, int n, int scale) Construct an instance of a Gamma function, computed using the Lanczos approximation.

Method Summary

Modifier and Type	Method and Description
double	evaluate(double x) Evaluate y = f(x).

Methods inherited from class com.numericalmethod.suanshu.analysis.function.rn2r1.univariate.UnivariateRealFunction

dimensionOfDomain, dimensionOfRange, evaluate

Methods inherited from class java.lang.Object

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

Constructor Detail

GammaLanczos

public GammaLanczos()

Construct an instance of a Gamma function, computed using the Lanczos approximation.

GammaLanczos

public GammaLanczos(double g,
                    int n,
                    int scale)

Construct an instance of a Gamma function, computed using the Lanczos approximation.

Recommended settings are

g = 607.0 / 128.0; n = 15; scale = 30;

Parameters:

g - g

n - n

scale - precision

Method Detail

evaluate

public double evaluate(double x)

Description copied from class: UnivariateRealFunction

Evaluate y = f(x).

Specified by:

evaluate in interface Gamma

Specified by:

evaluate in class UnivariateRealFunction

Parameters:

x - x

Returns:

f(x)