dragon.ir.classification.featureselection

Interface FeatureSelector

All Known Implementing Classes:

AbstractFeatureSelector, ChiFeatureSelector, DocFrequencySelector, InfoGainFeatureSelector, MutualInfoFeatureSelector, NullFeatureSelector

public interface FeatureSelector

Interface of feature selector which often work tegether with text classifiers.

Copyright: Copyright (c) 2005

Company: IST, Drexel University

Version:

1.0

Author:

Davis Zhou

Method Summary

Modifier and Type	Method and Description
int	getSelectedFeatureNum()
boolean	isSelected(int originalFeatureIndex)
int	map(int originalFeatureIndex) Map the old feature index to the index in the new feature space.
void	setSelectedFeatures(int[] selectedFeatures) Manually set selected features.
void	train(IndexReader indexReader, DocClassSet trainingSet) This method chooses a subset of features for text classification
void	train(SparseMatrix doctermMatrix, DocClassSet trainingSet) This method chooses a subset of features for text classification.

Method Detail

train

void train(SparseMatrix doctermMatrix,
           DocClassSet trainingSet)

This method chooses a subset of features for text classification. Some implmentations such as DocFrequencySelector and InfoGainFeatureSelector do not support this method.

Parameters:

doctermMatrix - the document-term matrix a classifer is working on

trainingSet - the labeled training document set

train

void train(IndexReader indexReader,
           DocClassSet trainingSet)

This method chooses a subset of features for text classification

Parameters:

indexReader - the index reader a classifer is working on

trainingSet - the labeled training document set

isSelected

boolean isSelected(int originalFeatureIndex)

Parameters:

originalFeatureIndex - the index of the feature in the old feature space

Returns:

true if the given feature is selected for text classification

getSelectedFeatureNum

int getSelectedFeatureNum()

Returns:

the number of selected features

map

int map(int originalFeatureIndex)

Map the old feature index to the index in the new feature space.

Parameters:

originalFeatureIndex - the index of the feature before feature selection

Returns:

the index of the feature the new space. If the feature is not selected, it will return -1.

setSelectedFeatures

void setSelectedFeatures(int[] selectedFeatures)

Manually set selected features. Usually used in testing stage.

Parameters:

selectedFeatures - each elements contains the index of the selected feature in the old feature space. The selected feature must be in the ascending order in the input array.