java.lang.Object
- cern.colt.PersistentObject
- - cern.jet.random.AbstractDistribution
  - - cern.jet.random.AbstractDiscreteDistribution
    - - cern.jet.random.Poisson

All Implemented Interfaces:

DoubleFunction, IntFunction, java.io.Serializable, java.lang.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.

Version:

1.0, 09/24/99

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type	Field	Description
`protected double`	`c_pm`
`protected double`	`dl`
`protected double`	`dr`
`protected double`	`f1`
`protected double`	`f2`
`protected double`	`f4`
`protected double`	`f5`
`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 Poisson`	`shared`
`protected static double`	`SWITCH_MEAN`

Fields inherited from class cern.jet.random.AbstractDistribution
randomGenerator

Fields inherited from class cern.colt.PersistentObject
serialVersionUID

Constructor Summary

Constructors
Constructor Description

Poisson(double mean, RandomEngine randomGenerator)
Constructs a poisson distribution.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`double`	`cdf(int k)`	Returns the cumulative distribution function.
`java.lang.Object`	`clone()`	Returns a deep copy of the receiver; the copy will produce identical sequences.
`private static double`	`f(int k, double l_nu, double c_pm)`
`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.
`java.lang.String`	`toString()`	Returns a String representation of the receiver.
`private static void`	`xstaticSetRandomGenerator(RandomEngine randomGenerator)`	Sets the uniform random number generated shared by all static methods.

Methods inherited from class cern.jet.random.AbstractDiscreteDistribution
nextDouble

Methods inherited from class cern.jet.random.AbstractDistribution
apply, apply, getRandomGenerator, makeDefaultGenerator, setRandomGenerator

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

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

shared
```
protected static Poisson shared
```

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 java.lang.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:
  
  a copy of the receiver.
- f
```
private static double f(int k,
                        double l_nu,
                        double c_pm)
```
- nextInt
```
public int nextInt()
```
  Returns a random number from the distribution.
  
  Specified by:
  
  nextInt in class AbstractDiscreteDistribution
- 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 java.lang.String toString()
```
  Returns a String representation of the receiver.
  
  Overrides:
  
  toString in class java.lang.Object
- xstaticSetRandomGenerator
```
private static void xstaticSetRandomGenerator(RandomEngine randomGenerator)
```
  Sets the uniform random number generated shared by all static methods.
  
  Parameters:
  
  randomGenerator - the new uniform random number generator to be shared.

Class Poisson

Field Summary

Fields inherited from class cern.jet.random.AbstractDistribution

Fields inherited from class cern.colt.PersistentObject

Constructor Summary

Method Summary

Methods inherited from class cern.jet.random.AbstractDiscreteDistribution

Methods inherited from class cern.jet.random.AbstractDistribution

Methods inherited from class java.lang.Object

Field Detail

mean

my_old

p

q

p0

pp

llll

my_last

ll

k2

k4

k1

k5

dl

dr

r1

r2

r4

r5

lr

l_my

c_pm

f1

f2

f4

f5

p1

p2

p3

p4

p5

p6

m

MEAN_MAX

SWITCH_MEAN

shared

Constructor Detail

Poisson

Method Detail

cdf

clone

f

nextInt

nextInt

pdf

setMean

staticNextInt

toString

xstaticSetRandomGenerator