Gamma
cern.jet.stat

Class Gamma



  • public class Gammaextends Constants
    Gamma and Beta functions.

    Implementation:

    Some code taken and adapted from the Java 2D Graph Package 2.4, which in turn is a port from the Cephes 2.2 Math Library (C). Most Cephes code (missing from the 2D Graph Package) directly ported.
    • Method Summary

      Methods 
      Modifier and TypeMethod and Description
      static doublebeta(double a, double b)
      Returns the beta function of the arguments.
      static doublegamma(double x)
      Returns the Gamma function of the argument.
      static doubleincompleteBeta(double aa, double bb, double xx)
      Returns the Incomplete Beta Function evaluated from zero to xx; formerly named ibeta.
      static doubleincompleteGamma(double a, double x)
      Returns the Incomplete Gamma function; formerly named igamma.
      static doubleincompleteGammaComplement(double a, double x)
      Returns the Complemented Incomplete Gamma function; formerly named igamc.
      static doublelogGamma(double x)
      Returns the natural logarithm of the gamma function; formerly named lgamma.
    • Method Detail

      • beta

        public static double beta(double a,          double b)                   throws ArithmeticException
        Returns the beta function of the arguments.
                           -     -                  | (a) | (b) beta( a, b )  =  -----------.                     -                    | (a+b) 
        Throws:
        ArithmeticException
      • incompleteBeta

        public static double incompleteBeta(double aa,                    double bb,                    double xx)                             throws ArithmeticException
        Returns the Incomplete Beta Function evaluated from zero to xx; formerly named ibeta.
        Parameters:
        aa - the alpha parameter of the beta distribution.
        bb - the beta parameter of the beta distribution.
        xx - the integration end point.
        Throws:
        ArithmeticException
      • incompleteGamma

        public static double incompleteGamma(double a,                     double x)                              throws ArithmeticException
        Returns the Incomplete Gamma function; formerly named igamma.
        Parameters:
        a - the parameter of the gamma distribution.
        x - the integration end point.
        Throws:
        ArithmeticException
      • incompleteGammaComplement

        public static double incompleteGammaComplement(double a,                               double x)                                        throws ArithmeticException
        Returns the Complemented Incomplete Gamma function; formerly named igamc.
        Parameters:
        a - the parameter of the gamma distribution.
        x - the integration start point.
        Throws:
        ArithmeticException

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