net.sf.doodleproject.numerics4j.statistics.distribution
Class PoissonDistribution

java.lang.Object
  net.sf.doodleproject.numerics4j.statistics.distribution.DiscreteDistribution
      net.sf.doodleproject.numerics4j.statistics.distribution.PoissonDistribution

All Implemented Interfaces:

Distribution

public class PoissonDistribution
extends DiscreteDistribution

The Poisson distribution.

References:

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

Since:

1.2

Version:

$Revision: 1.3 $ $Date: 2007/11/18 23:51:21 $

Constructor Summary

PoissonDistribution()
Default distribution.

PoissonDistribution(double m)
Create a distribution with the given mean.

Method Summary

double	cumulativeProbability(int x) The CDF for this distribution.
double	getMean() Access the mean.
int	inverseCumulativeProbability(double p) The inverse CDF for this distribution.
double	probability(int x) The PMF for this distribution.
void	setMean(double m) Modify the mean.

Methods inherited from class net.sf.doodleproject.numerics4j.statistics.distribution.DiscreteDistribution

findInverseCumulativeProbability, simpleCumulativeProbability

Methods inherited from class java.lang.Object

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

Constructor Detail

PoissonDistribution

public PoissonDistribution()

Default distribution. The means is set to one.

PoissonDistribution

public PoissonDistribution(double m)

Create a distribution with the given mean.

Parameters:

m - the mean.

Method Detail

cumulativeProbability

public double cumulativeProbability(int x)
                             throws NumericException

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

Specified by:

cumulativeProbability in class DiscreteDistribution

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.

inverseCumulativeProbability

public int inverseCumulativeProbability(double p)
                                 throws NumericException

The inverse CDF for this distribution. This method returns the largest x such that, P(X ≤ x) ≤ p. The return value must also satisfy P(X ≥ x) &ge 1 - p.

Specified by:

inverseCumulativeProbability in class DiscreteDistribution

Parameters:

p - the cumulative probability.

Returns:

x

Throws:

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

probability

public double probability(int x)

The PMF for this distribution. This method returns P(X = x).

Specified by:

probability in class DiscreteDistribution

Parameters:

x - the value at which the probability is evaluated.

Returns:

PMF for this distribution.

getMean

public double getMean()

Access the mean.

Returns:

the mean.

setMean

public void setMean(double m)

Modify the mean.

Parameters:

m - the new mean value.