Poisson
cern.jet.random

Class Poisson

• All Implemented Interfaces:
DoubleFunction, IntFunction, Serializable, Cloneable

public class Poisson
extends AbstractDiscreteDistribution
Poisson distribution (quick); See the math definition and animated definition.

p(k) = (mean^k / k!) * exp(-mean) for k >= 0.

Valid parameter ranges: mean > 0. Note: if mean <= 0.0 then always returns zero.

Instance methods operate on a user supplied uniform random number generator; they are unsynchronized.

Static methods operate on a default uniform random number generator; they are synchronized.

Implementation: High performance implementation. Patchwork Rejection/Inversion method.

This is a port of pprsc.c from the C-RAND / WIN-RAND library. C-RAND's implementation, in turn, is based upon

H. Zechner (1994): Efficient sampling from continuous and discrete unimodal distributions, Doctoral Dissertation, 156 pp., Technical University Graz, Austria.

Also see

Stadlober E., H. Zechner (1999), The patchwork rejection method for sampling from unimodal distributions, to appear in ACM Transactions on Modelling and Simulation.

Serialized Form

• Constructor Summary

Constructors
Constructor and Description
Poisson(double mean, RandomEngine randomGenerator)
Constructs a poisson distribution.
• Method Summary

Methods
Modifier and Type Method and Description
double cdf(int k)
Returns the cumulative distribution function.
Object clone()
Returns a deep copy of the receiver; the copy will produce identical sequences.
int nextInt()
Returns a random number from the distribution.
int nextInt(double theMean)
Returns a random number from the distribution; bypasses the internal state.
double pdf(int k)
Returns the probability distribution function.
void setMean(double mean)
Sets the mean.
static int staticNextInt(double mean)
Returns a random number from the distribution with the given mean.
String toString()
Returns a String representation of the receiver.
• Methods inherited from class cern.jet.random.AbstractDiscreteDistribution

nextDouble
• Constructor Detail

• Poisson

public Poisson(double mean,
RandomEngine randomGenerator)
Constructs a poisson distribution. Example: mean=1.0.
• Method Detail

• cdf

public double cdf(int k)
Returns the cumulative distribution function.
• clone

public Object clone()
Returns a deep copy of the receiver; the copy will produce identical sequences. After this call has returned, the copy and the receiver have equal but separate state.
Overrides:
clone in class AbstractDistribution
Returns:
• nextInt

public int nextInt(double theMean)
Returns a random number from the distribution; bypasses the internal state.
• pdf

public double pdf(int k)
Returns the probability distribution function.
• setMean

public void setMean(double mean)
Sets the mean.
• staticNextInt

public static int staticNextInt(double mean)
Returns a random number from the distribution with the given mean.
• toString

public String toString()
Returns a String representation of the receiver.
Overrides:
toString in class Object