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

Class Trigamma

java.lang.Object

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

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

All Implemented Interfaces:

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

public class Trigamma
extends UnivariateRealFunction

The trigamma function is defined as the logarithmic derivative of the digamma function. That is, \[ \psi_1(z) = \frac{d}{dz} \psi(z) \] This implementation is based on Algorithm 121.

See Also:

• "B. E. Schneider, "Algorithm 121: Trigamma Function," JSTOR. Vol. 27, No. 1, 1978."
• Wikipedia: Trigamma function
• "http://pmtksupport.googlecode.com/svn/trunk/lightspeed2.3/trigamma.m"
• "http://www.math.mcmaster.ca/peter/s743/trigamma.html"
• "http://lib.stat.cmu.edu/apstat/121"

, 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
Trigamma()

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

Trigamma

public Trigamma()

Method Detail

evaluate

public double evaluate(double x)

Description copied from class: UnivariateRealFunction

Evaluate y = f(x).

Specified by:

evaluate in class UnivariateRealFunction

Parameters:

x - x

Returns:

f(x)