org.apache.commons.math.distribution
Interface PoissonDistribution

All Superinterfaces:

DiscreteDistribution, Distribution, IntegerDistribution

All Known Implementing Classes:

PoissonDistributionImpl

public interface PoissonDistribution

extends IntegerDistribution

Interface representing the Poisson Distribution.

References:

• Poisson distribution

Version:

$Revision: 1.2 $ $Date: 2004/11/07 20:39:15 $

Method Summary

double	getMean() Get the mean for the distribution.
double	normalApproximateProbability(int x) Calculates the Poisson distribution function using a normal approximation.
void	setMean(double p) Set the mean for the distribution.

Methods inherited from interface org.apache.commons.math.distribution.IntegerDistribution

cumulativeProbability, cumulativeProbability, inverseCumulativeProbability, probability

Methods inherited from interface org.apache.commons.math.distribution.DiscreteDistribution

probability

Methods inherited from interface org.apache.commons.math.distribution.Distribution

cumulativeProbability, cumulativeProbability

Method Detail

getMean

public double getMean()

Get the mean for the distribution.

Returns:

the mean for the distribution.

setMean

public void setMean(double p)

Set the mean for the distribution. The parameter value must be positive; otherwise an IllegalArgument is thrown.

Parameters:

p - the mean

Throws:

IllegalArgumentException - if p ≤ 0

normalApproximateProbability

public double normalApproximateProbability(int x)
                                    throws MathException

Calculates the Poisson distribution function using a normal approximation.

Parameters:

x - the upper bound, inclusive

Returns:

the distribution function value calculated using a normal approximation

Throws:

MathException - if an error occurs computing the normal approximation