net.sf.classifier4J.bayesian
Class BayesianClassifier

java.lang.Object
  |
  +--net.sf.classifier4J.AbstractClassifier
        |
        +--net.sf.classifier4J.AbstractCategorizedTrainableClassifier
              |
              +--net.sf.classifier4J.bayesian.BayesianClassifier

All Implemented Interfaces:

ICategorisedClassifier, IClassifier, ITrainable, ITrainableClassifier

public class BayesianClassifier

extends AbstractCategorizedTrainableClassifier

A implementation of IClassifier based on Bayes' theorem (see http://www.wikipedia.org/wiki/Bayes_theorem).

The basic usage pattern for this class is:

1. Create a instance of IWordsDataSource
2. Create a new instance of BayesianClassifier, passing the IWordsDataSource to the constructor
3. Call IClassifier.classify(java.lang.String) or IClassifier.isMatch(java.lang.String)

For example:
IWordsDataSource wds = new SimpleWordsDataSource();
IClassifier classifier = new BayesianClassifier(wds);
System.out.println( "Matches = " + classifier.classify("This is a sentence") );

Author:

Nick Lothian, Peter Leschev

Field Summary

Fields inherited from class net.sf.classifier4J.AbstractClassifier

cutoff

Fields inherited from interface net.sf.classifier4J.ICategorisedClassifier

DEFAULT_CATEGORY

Fields inherited from interface net.sf.classifier4J.IClassifier

DEFAULT_CUTOFF, LOWER_BOUND, NEUTRAL_PROBABILITY, UPPER_BOUND

Constructor Summary

BayesianClassifier()
Default constructor that uses the SimpleWordsDataSource & a DefaultTokenizer (set to BREAK_ON_WORD_BREAKS).

BayesianClassifier(IWordsDataSource wd)
Constructor for BayesianClassifier that specifies a datasource.

BayesianClassifier(IWordsDataSource wd, ITokenizer tokenizer)
Constructor for BayesianClassifier that specifies a datasource & tokenizer

BayesianClassifier(IWordsDataSource wd, ITokenizer tokenizer, IStopWordProvider swp)
Constructor for BayesianClassifier that specifies a datasource, tokenizer and stop words provider

Method Summary

protected double	calculateOverallProbability(WordProbability[] wps) NOTE: Override this method with care.
double	classify(java.lang.String category, java.lang.String input) Function to determine the probability string matches a criteria for a given category.
protected double	classify(java.lang.String category, java.lang.String[] words)
IStopWordProvider	getStopWordProvider()
ITokenizer	getTokenizer()
IWordsDataSource	getWordsDataSource()
boolean	isCaseSensitive()
boolean	isMatch(java.lang.String category, java.lang.String input) Function to determine if a string matches a criteria for a given category
protected boolean	isMatch(java.lang.String category, java.lang.String[] input)
protected static double	normaliseSignificance(double sig)
void	setCaseSensitive(boolean b)
void	teachMatch(java.lang.String category, java.lang.String input)
protected void	teachMatch(java.lang.String category, java.lang.String[] words)
void	teachNonMatch(java.lang.String category, java.lang.String input)
protected void	teachNonMatch(java.lang.String category, java.lang.String[] words)
java.lang.String	toString()
protected java.lang.String	transformWord(java.lang.String word) Allows transformations to be done to word.

Methods inherited from class net.sf.classifier4J.AbstractCategorizedTrainableClassifier

classify, teachMatch, teachNonMatch

Methods inherited from class net.sf.classifier4J.AbstractClassifier

getMatchCutoff, isMatch, isMatch, setMatchCutoff

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.classifier4J.IClassifier

isMatch, isMatch, setMatchCutoff

Constructor Detail

BayesianClassifier

public BayesianClassifier()

Default constructor that uses the SimpleWordsDataSource & a DefaultTokenizer (set to BREAK_ON_WORD_BREAKS).

BayesianClassifier

public BayesianClassifier(IWordsDataSource wd)

Constructor for BayesianClassifier that specifies a datasource. The DefaultTokenizer (set to BREAK_ON_WORD_BREAKS) will be used.

Parameters:

wd - a IWordsDataSource

BayesianClassifier

public BayesianClassifier(IWordsDataSource wd,
                          ITokenizer tokenizer)

Constructor for BayesianClassifier that specifies a datasource & tokenizer

Parameters:

wd - a IWordsDataSource

tokenizer - a ITokenizer

BayesianClassifier

public BayesianClassifier(IWordsDataSource wd,
                          ITokenizer tokenizer,
                          IStopWordProvider swp)

Constructor for BayesianClassifier that specifies a datasource, tokenizer and stop words provider

Parameters:

wd - a IWordsDataSource

tokenizer - a ITokenizer

swp - a IStopWordProvider

Method Detail

isMatch

public boolean isMatch(java.lang.String category,
                       java.lang.String input)
                throws WordsDataSourceException

Description copied from interface: ICategorisedClassifier

Function to determine if a string matches a criteria for a given category

Parameters:

category - the category to check against

input - the string to classify

Returns:

true if the input string has a probability >= the cutoff probability of matching

WordsDataSourceException

See Also:

ICategorisedClassifier.isMatch(java.lang.String, java.lang.String)

classify

public double classify(java.lang.String category,
                       java.lang.String input)
                throws WordsDataSourceException

Description copied from interface: ICategorisedClassifier

Function to determine the probability string matches a criteria for a given category.

Parameters:

category - the category to check against

input - the string to classify

Returns:

the likelyhood that this string is a match for this net.sf.classifier4J. 1 means 100% likely.

WordsDataSourceException

See Also:

ICategorisedClassifier.classify(java.lang.String, java.lang.String)

teachMatch

public void teachMatch(java.lang.String category,
                       java.lang.String input)
                throws WordsDataSourceException

WordsDataSourceException

teachNonMatch

public void teachNonMatch(java.lang.String category,
                          java.lang.String input)
                   throws WordsDataSourceException

WordsDataSourceException

isMatch

protected boolean isMatch(java.lang.String category,
                          java.lang.String[] input)
                   throws WordsDataSourceException

WordsDataSourceException

classify

protected double classify(java.lang.String category,
                          java.lang.String[] words)
                   throws WordsDataSourceException

WordsDataSourceException

teachMatch

protected void teachMatch(java.lang.String category,
                          java.lang.String[] words)
                   throws WordsDataSourceException

WordsDataSourceException

teachNonMatch

protected void teachNonMatch(java.lang.String category,
                             java.lang.String[] words)
                      throws WordsDataSourceException

WordsDataSourceException

transformWord

protected java.lang.String transformWord(java.lang.String word)

Allows transformations to be done to word. This implementation transforms the word to lowercase if the classifier is in case-insenstive mode.

Parameters:

word -

Returns:

the transformed word

Throws:

java.lang.IllegalArgumentException - if a null is passed

calculateOverallProbability

protected double calculateOverallProbability(WordProbability[] wps)

NOTE: Override this method with care. There is a good chance it will be removed or have signature changes is later versions.

normaliseSignificance

protected static double normaliseSignificance(double sig)

isCaseSensitive

public boolean isCaseSensitive()

Returns:

true if the classifier is case sensitive, false otherwise (false by default)

setCaseSensitive

public void setCaseSensitive(boolean b)

Parameters:

b - True if the classifier should be case sensitive, false otherwise

getWordsDataSource

public IWordsDataSource getWordsDataSource()

Returns:

the IWordsDataSource used by this classifier

getTokenizer

public ITokenizer getTokenizer()

Returns:

the ITokenizer used by this classifier

getStopWordProvider

public IStopWordProvider getStopWordProvider()

Returns:

the IStopWordProvider used by this classifier

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object