JSci.maths.statistics
Class PoissonDistribution

java.lang.Object
  JSci.maths.statistics.ProbabilityDistribution
      JSci.maths.statistics.PoissonDistribution

public final class PoissonDistribution
extends ProbabilityDistribution

The PoissonDistribution class provides an object for encapsulating Poisson distributions.

Constructor Summary

PoissonDistribution(double interval)
Constructs a Poisson distribution.

Method Summary

double	cumulative(double X) Cumulative Poisson distribution function.
double	getIntervalParameter() Returns the interval parameter.
double	getMean() Returns the mean.
double	getVariance() Returns the variance.
double	inverse(double probability) Inverse of the cumulative Poisson distribution function.
double	probability(double X) Probability density function of a Poisson distribution.

Methods inherited from class JSci.maths.statistics.ProbabilityDistribution

checkRange, checkRange, findRoot

Methods inherited from class java.lang.Object

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

Constructor Detail

PoissonDistribution

public PoissonDistribution(double interval)

Constructs a Poisson distribution.

Parameters:

interval - the interval.

Method Detail

getIntervalParameter

public double getIntervalParameter()

Returns the interval parameter.

getMean

public double getMean()

Returns the mean.

getVariance

public double getVariance()

Returns the variance.

probability

public double probability(double X)

Probability density function of a Poisson distribution. P(X) = ^Xe^-/X!.

Specified by:

probability in class ProbabilityDistribution

Parameters:

X - should be integer-valued.

Returns:

the probability that a stochastic variable x has the value X, i.e. P(x=X).

cumulative

public double cumulative(double X)

Cumulative Poisson distribution function.

Specified by:

cumulative in class ProbabilityDistribution

Parameters:

X - should be integer-valued.

Returns:

the probability that a stochastic variable x is less then X, i.e. P(x<X).

inverse

public double inverse(double probability)

Inverse of the cumulative Poisson distribution function.

Specified by:

inverse in class ProbabilityDistribution

Returns:

the value X for which P(x<X).