edu.cmu.minorthird.classify.algorithms.random
Class Poisson

java.lang.Object
  edu.cmu.minorthird.classify.algorithms.random.Poisson

public class Poisson
extends java.lang.Object

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.

Version:

1.0, 09/24/99

Author:

wolfgang.hoschek@cern.ch, Edoardo Airoldi

Field Summary

protected double	c_pm
protected double	dl
protected double	dr
protected double	f1
protected double	f2
protected double	f4
protected double	f5
protected RandomElement	gen
protected int	k1
protected int	k2
protected int	k4
protected int	k5
protected double	l_my
protected double	ll
protected int	llll
protected double	lr
protected int	m
protected double	mean
protected static double	MEAN_MAX
protected double	my_last
protected double	my_old
protected double	p
protected double	p0
protected double	p1
protected double	p2
protected double	p3
protected double	p4
protected double	p5
protected double	p6
protected double[]	pp
protected double	q
protected double	r1
protected double	r2
protected double	r4
protected double	r5
protected static double	SWITCH_MEAN

Constructor Summary

Poisson(double mean)
Constructs a poisson distribution.

Method Summary

int	nextInt() Returns a random number from the distribution.
int	nextInt(double theMean) Returns a random number from the distribution.
void	setMean(double mean) Sets the mean.
java.lang.String	toString() Returns a String representation of the receiver.

Methods inherited from class java.lang.Object

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

Field Detail

gen

protected RandomElement gen

mean

protected double mean

my_old

protected double my_old

p

protected double p

q

protected double q

p0

protected double p0

pp

protected double[] pp

llll

protected int llll

my_last

protected double my_last

ll

protected double ll

k2

protected int k2

k4

protected int k4

k1

protected int k1

k5

protected int k5

dl

protected double dl

dr

protected double dr

r1

protected double r1

r2

protected double r2

r4

protected double r4

r5

protected double r5

lr

protected double lr

l_my

protected double l_my

c_pm

protected double c_pm

f1

protected double f1

f2

protected double f2

f4

protected double f4

f5

protected double f5

p1

protected double p1

p2

protected double p2

p3

protected double p3

p4

protected double p4

p5

protected double p5

p6

protected double p6

m

protected int m

MEAN_MAX

protected static final double MEAN_MAX

See Also:

Constant Field Values

SWITCH_MEAN

protected static final double SWITCH_MEAN

See Also:

Constant Field Values

Constructor Detail

Poisson

public Poisson(double mean)

Constructs a poisson distribution. Example: mean=1.0.

Method Detail

nextInt

public int nextInt()

Returns a random number from the distribution.

nextInt

public int nextInt(double theMean)

Returns a random number from the distribution.

setMean

public void setMean(double mean)

Sets the mean.

toString

public java.lang.String toString()

Returns a String representation of the receiver.

Overrides:

toString in class java.lang.Object