Class Erlang

java.lang.Object

random.AbstractDistribution

random.Erlang

All Implemented Interfaces:

Distribution, StorableDistribution

public class Erlang
extends AbstractDistribution
implements Distribution

This is the Erlang distribution.

Copyright (c) 2003
Politecnico di Milano - dipartimento di Elettronica e Informazione

Author:

Fabrizio Frontera - ffrontera@yahoo.it, Modified by Stefano Omini, 7/5/2004

Field Summary

Fields inherited from class AbstractDistribution

engine

Constructor Summary

Constructors

Constructor	Description
Erlang()	This is the constructor.

Method Summary

Modifier and Type	Method	Description
double	cdf(double x, Parameter p)	This method is used to obtain from the distribution its cumulative distribution function evaluated where required by the user.
double	nextRand(Parameter p)	This method is used to obtain from the distribution the next number distributed according to the distribution parameter.
double	pdf(double x, Parameter p)	This method is used to obtain from the distribution its probability distribution function evaluated where required by the user.
double	theorMean(Parameter p)	This method is used to obtain from the distribution the value of its own theoretic mean.
double	theorVariance(Parameter p)	This method is used to obtain from the distribution the value of its own theoretic variance.

Methods inherited from class AbstractDistribution

setRandomEngine

Methods inherited from class Object

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

Methods inherited from interface Distribution

setRandomEngine

Constructor Details

Erlang

public Erlang()

This is the constructor. It creates a new erlang distribution which is defined from pdf:

           (alpha^r)       (r-1)     (-alpha*x)
pdf(x) = -------------  * x       * e
          gammaFun(r)

where r is the "shape" parameter, alpha is the "scale" parameter and gammaFun is the "Eulero" function.

Method Details

pdf

public double pdf(double x,
 Parameter p)
           throws IncorrectDistributionParameterException

This method is used to obtain from the distribution its probability distribution function evaluated where required by the user.

Specified by:

pdf in interface Distribution

Parameters:

x - double indicating where to evaluate the pdf.

p - parameter of the erlang distribution.

Returns:

double with the probability distribution function evaluated in x.

Throws:

IncorrectDistributionParameterException

cdf

public double cdf(double x,
 Parameter p)
           throws IncorrectDistributionParameterException

This method is used to obtain from the distribution its cumulative distribution function evaluated where required by the user.

Specified by:

cdf in interface Distribution

Parameters:

x - double indicating where to evaluate the cdf.

p - parameter of the erlang distribution.

Returns:

double with the cumulative distribution function evaluated in x.

Throws:

IncorrectDistributionParameterException

theorMean

public double theorMean(Parameter p)
                 throws IncorrectDistributionParameterException

This method is used to obtain from the distribution the value of its own theoretic mean.

Specified by:

theorMean in interface Distribution

Parameters:

p - parameter of the erlang distribution.

Returns:

double with the theoretic mean of the distribution. The theoretic mean is calculated as r/alpha.

Throws:

IncorrectDistributionParameterException

theorVariance

public double theorVariance(Parameter p)
                     throws IncorrectDistributionParameterException

This method is used to obtain from the distribution the value of its own theoretic variance.

Specified by:

theorVariance in interface Distribution

Parameters:

p - parameter of the erlang distribution.

Returns:

double with the theoretic variance of the distribution. The theoretic variance is calculated as r/(alpha^2).

Throws:

IncorrectDistributionParameterException

nextRand

public double nextRand(Parameter p)
                throws IncorrectDistributionParameterException

This method is used to obtain from the distribution the next number distributed according to the distribution parameter.

Specified by:

nextRand in interface Distribution

Parameters:

p - parameter of the erlang distribution.

Returns:

double with the next random number of this distribution.

Throws:

IncorrectDistributionParameterException