weka.estimators
Class PoissonEstimator

java.lang.Object
  weka.estimators.PoissonEstimator

All Implemented Interfaces:

Estimator, java.io.Serializable

public class PoissonEstimator

extends java.lang.Object

implements Estimator

Simple probability estimator that places a single Poisson distribution over the observed values.

Version:

$Revision: 1.4 $

Author:

Len Trigg (trigg@cs.waikato.ac.nz)

See Also:

Serialized Form

Field Summary

private double	m_Lambda The average number of times an event occurs in an interval.
private double	m_NumValues The number of values seen
private double	m_SumOfValues The sum of the values seen

Constructor Summary

PoissonEstimator()

Method Summary

void	addValue(double data, double weight) Add a new data value to the current estimator.
double	getProbability(double data) Get a probability estimate for a value
private double	logFac(double x) Calculates the log factorial of a number.
static void	main(java.lang.String[] argv) Main method for testing this class.
private double	Poisson(double x) Returns value for Poisson distribution
java.lang.String	toString() Display a representation of this estimator

Methods inherited from class java.lang.Object

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

Field Detail

m_NumValues

private double m_NumValues

The number of values seen

m_SumOfValues

private double m_SumOfValues

The sum of the values seen

m_Lambda

private double m_Lambda

The average number of times an event occurs in an interval.

Constructor Detail

PoissonEstimator

public PoissonEstimator()

Method Detail

logFac

private double logFac(double x)

Calculates the log factorial of a number.

Parameters:

x - input number.

Returns:

log factorial of x.

Poisson

private double Poisson(double x)

Returns value for Poisson distribution

Parameters:

x - the argument to the kernel function

Returns:

the value for a Poisson kernel

addValue

public void addValue(double data,
                     double weight)

Add a new data value to the current estimator.

Specified by:

addValue in interface Estimator

Parameters:

data - the new data value

weight - the weight assigned to the data value

getProbability

public double getProbability(double data)

Get a probability estimate for a value

Specified by:

getProbability in interface Estimator

Parameters:

data - the value to estimate the probability of

Returns:

the estimated probability of the supplied value

toString

public java.lang.String toString()

Display a representation of this estimator

main

public static void main(java.lang.String[] argv)

Main method for testing this class.

Parameters:

argv - should contain a sequence of numeric values