edu.udo.cs.yale.operator.features
Class EquivalentAttributeRemoval

java.lang.Object
  edu.udo.cs.yale.operator.features.IndividualOperator
      edu.udo.cs.yale.operator.features.EquivalentAttributeRemoval

All Implemented Interfaces:

PopulationOperator

public class EquivalentAttributeRemoval
extends IndividualOperator

If the example set contain two equivalent attributes, the longer representation is removed. The length is calculated as the number of nested brackets. The equivalency probe is not done by structural comparison. The attribute values of the equations in question are randomly sampled and the equation results compared. If the difference is less than epsilon for k trials, the equations are probably equivalent. At least they produce similar values.
The values of the attributes are sampled in the range of the minimum and maximum values of the attribute. This ensures equivalency or at least very similar values for the definition range in question. Therefore a MemoryExampleTable is constructed and filled with random values. Then a AttributeParser is used to construct the attributes values.

Version:

$Id: EquivalentAttributeRemoval.java,v 2.17 2006/03/27 13:21:58 ingomierswa Exp $

Author:

Ingo Mierswa

Field Summary

private double	epsilon If the difference is smaller than epsilon, the attributes are considered as equivalent.
private int	numberOfSamples Indicates the number of examples which should be randomly generated to check equivalency.
private RandomGenerator	random The random generator for the example values.
private boolean	recalculateAttributeStatistics Recalculates attribute statistics before sampling.

Constructor Summary

EquivalentAttributeRemoval(int numberOfSamples, double epsilon, boolean recalculateAttributeStatistics, RandomGenerator random)
Creates a new equivalent attribute removal population operator.

Method Summary

private boolean	equivalent(ExampleSet exampleSet)
java.util.List<Individual>	operate(Individual individual) Subclasses must implement this method providing a list of new individuals.

Methods inherited from class edu.udo.cs.yale.operator.features.IndividualOperator

operate, performOperation

Methods inherited from class java.lang.Object

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

Field Detail

numberOfSamples

private int numberOfSamples

Indicates the number of examples which should be randomly generated to check equivalency.

epsilon

private double epsilon

If the difference is smaller than epsilon, the attributes are considered as equivalent.

recalculateAttributeStatistics

private boolean recalculateAttributeStatistics

Recalculates attribute statistics before sampling.

random

private RandomGenerator random

The random generator for the example values.

Constructor Detail

EquivalentAttributeRemoval

public EquivalentAttributeRemoval(int numberOfSamples,
                                  double epsilon,
                                  boolean recalculateAttributeStatistics,
                                  RandomGenerator random)

Creates a new equivalent attribute removal population operator.

Method Detail

operate

public java.util.List<Individual> operate(Individual individual)

Description copied from class: IndividualOperator

Subclasses must implement this method providing a list of new individuals. individual will be removed from the population so it might be useful to return a list of size 1 containing only the modified individual. If the original individual should also be part of the new population it must also be added to the result list.

Specified by:

operate in class IndividualOperator

equivalent

private boolean equivalent(ExampleSet exampleSet)