Class 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 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)