org.apache.commons.math.distribution
Class GammaDistributionImpl

java.lang.Object
  extended by org.apache.commons.math.distribution.AbstractDistribution
      extended by org.apache.commons.math.distribution.AbstractContinuousDistribution
          extended by org.apache.commons.math.distribution.GammaDistributionImpl
All Implemented Interfaces:
java.io.Serializable, ContinuousDistribution, Distribution, GammaDistribution

public class GammaDistributionImpl
extends AbstractContinuousDistribution
implements GammaDistribution, java.io.Serializable

The default implementation of GammaDistribution.

See Also:
Serialized Form

Constructor Summary
GammaDistributionImpl(double alpha, double beta)
          Create a new gamma distribution with the given alpha and beta values.
 
Method Summary
 double cumulativeProbability(double x)
          For this disbution, X, this method returns P(X < x).
 double getAlpha()
          Access the shape parameter, alpha
 double getBeta()
          Access the scale parameter, beta
 double inverseCumulativeProbability(double p)
          For this distribution, X, this method returns the critical point x, such that P(X < x) = p.
 void setAlpha(double alpha)
          Modify the shape parameter, alpha.
 void setBeta(double beta)
          Modify the scale parameter, beta.
 
Methods inherited from class org.apache.commons.math.distribution.AbstractDistribution
cumulativeProbability
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface org.apache.commons.math.distribution.Distribution
cumulativeProbability
 

Constructor Detail

GammaDistributionImpl

public GammaDistributionImpl(double alpha,
                             double beta)
Create a new gamma distribution with the given alpha and beta values.

Parameters:
alpha - the shape parameter.
beta - the scale parameter.
Method Detail

cumulativeProbability

public double cumulativeProbability(double x)
                             throws MathException
For this disbution, X, this method returns P(X < x). The implementation of this method is based on:

Specified by:
cumulativeProbability in interface Distribution
Parameters:
x - the value at which the CDF is evaluated.
Returns:
CDF for this distribution.
Throws:
MathException - if the cumulative probability can not be computed due to convergence or other numerical errors.

inverseCumulativeProbability

public double inverseCumulativeProbability(double p)
                                    throws MathException
For this distribution, X, this method returns the critical point x, such that P(X < x) = p.

Returns 0 for p=0 and Double.POSITIVE_INFINITY for p=1.

Specified by:
inverseCumulativeProbability in interface ContinuousDistribution
Overrides:
inverseCumulativeProbability in class AbstractContinuousDistribution
Parameters:
p - the desired probability
Returns:
x, such that P(X < x) = p
Throws:
MathException - if the inverse cumulative probability can not be computed due to convergence or other numerical errors.
java.lang.IllegalArgumentException - if p is not a valid probability.

setAlpha

public void setAlpha(double alpha)
Modify the shape parameter, alpha.

Specified by:
setAlpha in interface GammaDistribution
Parameters:
alpha - the new shape parameter.
Throws:
java.lang.IllegalArgumentException - if alpha is not positive.

getAlpha

public double getAlpha()
Access the shape parameter, alpha

Specified by:
getAlpha in interface GammaDistribution
Returns:
alpha.

setBeta

public void setBeta(double beta)
Modify the scale parameter, beta.

Specified by:
setBeta in interface GammaDistribution
Parameters:
beta - the new scale parameter.
Throws:
java.lang.IllegalArgumentException - if beta is not positive.

getBeta

public double getBeta()
Access the scale parameter, beta

Specified by:
getBeta in interface GammaDistribution
Returns:
beta.


jHepWork 1.1 (C) Chekanov