Class Digamma
- java.lang.Object
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- dev.nm.analysis.function.rn2r1.AbstractRealScalarFunction
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- dev.nm.analysis.function.rn2r1.univariate.AbstractUnivariateRealFunction
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- dev.nm.analysis.function.special.gamma.Digamma
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- All Implemented Interfaces:
Function<Vector,Double>
,RealScalarFunction
,UnivariateRealFunction
public class Digamma extends AbstractUnivariateRealFunction
The digamma function is defined as the logarithmic derivative of the gamma function. That is, \[ \psi(x) =\frac{d}{dx} \ln{\Gamma(x)}= \frac{\Gamma'(x)}{\Gamma(x)} \] This implementation is based on Algorithm 610.- See Also:
- "D. E. Amos, "Algorithm 610: A Portable FORTRAN Subroutine for Derivatives of the Psi Function," ACM Transactions on Mathematical Software (TOMS), Volume 9, Issue 4 (December 1983), p. 494 - 502."
- "Shanjie Zhang, Jianming Jin, Computation of Special Functions. Wiley-Interscience; Har/Dis edition (July 12, 1996)."
- Wikipedia: Digamma function
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Nested Class Summary
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Nested classes/interfaces inherited from interface dev.nm.analysis.function.Function
Function.EvaluationException
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Constructor Summary
Constructors Constructor Description Digamma()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description double
evaluate(double x)
Evaluate y = f(x).-
Methods inherited from class dev.nm.analysis.function.rn2r1.univariate.AbstractUnivariateRealFunction
evaluate
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Methods inherited from class dev.nm.analysis.function.rn2r1.AbstractRealScalarFunction
dimensionOfDomain, dimensionOfRange
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface dev.nm.analysis.function.Function
dimensionOfDomain, dimensionOfRange
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Method Detail
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evaluate
public double evaluate(double x)
Description copied from interface:UnivariateRealFunction
Evaluate y = f(x).- Parameters:
x
- x- Returns:
- f(x)
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