Package 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"

  • Constructor Details

    • Trigamma

      public Trigamma()

  • Method Details

    • evaluate

      public double evaluate(double x)
      Description copied from interface: UnivariateRealFunction
      Evaluate y = f(x).
      Parameters:
      x - x
      Returns:
      f(x)