dev.nm.analysis.function.special.gamma

Class Trigamma

java.lang.Object

dev.nm.analysis.function.rn2r1.AbstractRealScalarFunction

dev.nm.analysis.function.rn2r1.univariate.AbstractUnivariateRealFunction

dev.nm.analysis.function.special.gamma.Trigamma

All Implemented Interfaces:

Function<Vector,Double>, RealScalarFunction, UnivariateRealFunction

public class Trigamma
extends AbstractUnivariateRealFunction

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"

Nested Class Summary

Nested classes/interfaces inherited from interface dev.nm.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 dev.nm.analysis.function.rn2r1.univariate.AbstractUnivariateRealFunction

evaluate

Methods inherited from class dev.nm.analysis.function.rn2r1.AbstractRealScalarFunction

dimensionOfDomain, dimensionOfRange

Methods inherited from class java.lang.Object

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

Methods inherited from interface dev.nm.analysis.function.Function

dimensionOfDomain, dimensionOfRange

Constructor Detail

Trigamma

public Trigamma()

Method Detail

evaluate

public double evaluate(double x)

Description copied from interface: UnivariateRealFunction

Evaluate y = f(x).

Parameters:

x - x

Returns:

f(x)