org.apache.mahout.math.jet.stat
Class Gamma

java.lang.Object
  extended by org.apache.mahout.math.jet.math.Constants
      extended by org.apache.mahout.math.jet.stat.Gamma

public class Gamma
extends Constants

Partially deprecated until unit tests are in place. Until this time, this class/interface is unsupported.


Field Summary
 
Fields inherited from class org.apache.mahout.math.jet.math.Constants
BIG, BIG_INVERSE, LOGPI, MACHEP, MAXGAM, MAXLOG, MINLOG, SQRTH, SQTPI
 
Constructor Summary
protected Gamma()
          Makes this class non instantiable, but still let's others inherit from it.
 
Method Summary
static double beta(double alpha, double beta)
          Returns the beta function of the arguments.
static double gamma(double x)
          Returns the Gamma function of the argument.
static double incompleteBeta(double alpha, double beta, double xx)
          Returns the regularized Incomplete Beta Function evaluated from zero to xx; formerly named ibeta.
static double incompleteGamma(double alpha, double x)
          Returns the Incomplete Gamma function; formerly named igamma.
static double incompleteGammaComplement(double alpha, double x)
          Returns the Complemented Incomplete Gamma function; formerly named igamc.
static double logGamma(double x)
          Returns the natural logarithm of the gamma function; formerly named lgamma.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Gamma

protected Gamma()
Makes this class non instantiable, but still let's others inherit from it.

Method Detail

beta

public static double beta(double alpha,
                          double beta)
Returns the beta function of the arguments.
                   -     -
                  | (a) | (b)
 beta( a, b )  =  -----------.
                     -
                    | (a+b)
 

Parameters:
alpha -
beta -
Returns:
The beta function for given values of alpha and beta.

gamma

public static double gamma(double x)
Returns the Gamma function of the argument.


incompleteBeta

public static double incompleteBeta(double alpha,
                                    double beta,
                                    double xx)
Returns the regularized Incomplete Beta Function evaluated from zero to xx; formerly named ibeta. See http://en.wikipedia.org/wiki/Incomplete_beta_function#Incomplete_beta_function

Parameters:
alpha - the alpha parameter of the beta distribution.
beta - the beta parameter of the beta distribution.
xx - the integration end point.

incompleteGamma

public static double incompleteGamma(double alpha,
                                     double x)
Returns the Incomplete Gamma function; formerly named igamma.

Parameters:
alpha - the shape parameter of the gamma distribution.
x - the integration end point.
Returns:
The value of the unnormalized incomplete gamma function.

incompleteGammaComplement

public static double incompleteGammaComplement(double alpha,
                                               double x)
Returns the Complemented Incomplete Gamma function; formerly named igamc.

Parameters:
alpha - the shape parameter of the gamma distribution.
x - the integration start point.

logGamma

public static double logGamma(double x)
Returns the natural logarithm of the gamma function; formerly named lgamma.



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