jhplot.math.num.pdf

Class Gamma

java.lang.Object

jhplot.math.num.pdf.ContinuousDistribution

jhplot.math.num.pdf.Gamma

All Implemented Interfaces:

Distribution

public class Gamma
extends ContinuousDistribution

The Gamma distribution (1).

References:

1. Eric W. Weisstein. "Gamma Distribution." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/Gamma.html

Constructor Summary

Constructors

Constructor and Description
Gamma() Default constructor.
Gamma(double a, double b) Create a distribution with the given alpha and beta values.

Method Summary

Modifier and Type	Method and Description
double	cumulativeProbability(double x) The CDF for this distribution.
double	getAlpha() Access the alpha parameter.
double	getBeta() Access the beta parameter.
double	inverseCumulativeProbability(double p) The inverse CDF for this distribution.
void	setAlpha(double a) Modify the alpha parameter.
void	setBeta(double b) Modify the beta parameter.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Gamma

public Gamma()

Default constructor. Alpha and beta are both set to 1.

Gamma

public Gamma(double a,
             double b)

Create a distribution with the given alpha and beta values.

Parameters:

a - the alpha parameter.

b - the beta parameter.

Method Detail

cumulativeProbability

public double cumulativeProbability(double x)
                             throws NumericException

The CDF for this distribution. This method returns P(X < x).

Specified by:

cumulativeProbability in class ContinuousDistribution

Parameters:

x - the value at which the CDF is evaluated.

Returns:

CDF for this distribution.

Throws:

NumericException - if the cumulative probability can not be computed.

getAlpha

public double getAlpha()

Access the alpha parameter.

Returns:

the alpha parameter.

getBeta

public double getBeta()

Access the beta parameter.

Returns:

the beta parameter.

inverseCumulativeProbability

public double inverseCumulativeProbability(double p)
                                    throws NumericException

The inverse CDF for this distribution. This method returns x such that, P(X < x) = p.

Specified by:

inverseCumulativeProbability in class ContinuousDistribution

Parameters:

p - the cumulative probability.

Returns:

x

Throws:

NumericException - if the inverse cumulative probability can not be computed.

setAlpha

public void setAlpha(double a)

Modify the alpha parameter.

Parameters:

a - the new alpha value.

setBeta

public void setBeta(double b)

Modify the beta parameter.

Parameters:

b - the new beta value.