weka.attributeSelection
Class AttributeSelection

java.lang.Object
  |
  +--weka.attributeSelection.AttributeSelection

All Implemented Interfaces:

java.io.Serializable

public class AttributeSelection

extends java.lang.Object

implements java.io.Serializable

Attribute selection class. Takes the name of a search class and an evaluation class on the command line.

Valid options are:

-h
Display help.

-I
Specify the training arff file.

-C
The index of the attribute to use as the class.

-S

The full class name of the search method followed by search method options (if any).
Eg. -S "weka.attributeSelection.BestFirst -N 10"

-X
Perform a cross validation.

-N
Specify a random number seed. Use in conjuction with -X. (Default = 1).

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Example usage as the main of an attribute evaluator (called FunkyEvaluator):

 public static void main(String [] args) {
   try {
     ASEvaluator eval = new FunkyEvaluator();
     System.out.println(SelectAttributes(Evaluator, args));
   } catch (Exception e) {
     System.err.println(e.getMessage());
   }
 }
  

------------------------------------------------------------------------

Version:

$Revision: 1.31 $

Author:

Mark Hall (mhall@cs.waikato.ac.nz)

See Also:

Serialized Form

Constructor Summary

AttributeSelection()
constructor.

Method Summary

java.lang.String	CrossValidateAttributes() Perform a cross validation for attribute selection.
java.lang.String	CVResultsString() returns a string summarizing the results of repeated attribute selection runs on splits of a dataset.
static void	main(java.lang.String[] args) Main method for testing this class.
int	numberAttributesSelected() Return the number of attributes selected from the most recent run of attribute selection
double[][]	rankedAttributes() get the final ranking of the attributes.
Instance	reduceDimensionality(Instance in) reduce the dimensionality of a single instance to include only those attributes chosen by the last run of attribute selection.
Instances	reduceDimensionality(Instances in) reduce the dimensionality of a set of instances to include only those attributes chosen by the last run of attribute selection.
static java.lang.String	SelectAttributes(ASEvaluation ASEvaluator, java.lang.String[] options) Perform attribute selection with a particular evaluator and a set of options specifying search method and input file etc.
static java.lang.String	SelectAttributes(ASEvaluation ASEvaluator, java.lang.String[] options, Instances train) Perform attribute selection with a particular evaluator and a set of options specifying search method and options for the search method and evaluator.
void	SelectAttributes(Instances data) Perform attribute selection on the supplied training instances.
void	selectAttributesCVSplit(Instances split) Select attributes for a split of the data.
int[]	selectedAttributes() get the final selected set of attributes.
void	setEvaluator(ASEvaluation evaluator) set the attribute/subset evaluator
void	setFolds(int folds) set the number of folds for cross validation
void	setRanking(boolean r) produce a ranking (if possible with the set search and evaluator)
void	setSearch(ASSearch search) set the search method
void	setSeed(int s) set the seed for use in cross validation
void	setThreshold(double t) set the threshold by which to select features from a ranked list
void	setXval(boolean x) do a cross validation
java.lang.String	toResultsString() get a description of the attribute selection

Methods inherited from class java.lang.Object

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

Constructor Detail

AttributeSelection

public AttributeSelection()

constructor. Sets defaults for each member varaible. Default attribute evaluator is CfsSubsetEval; default search method is BestFirst.

Method Detail

numberAttributesSelected

public int numberAttributesSelected()
                             throws java.lang.Exception

Return the number of attributes selected from the most recent run of attribute selection

Returns:

the number of attributes selected

java.lang.Exception

selectedAttributes

public int[] selectedAttributes()
                         throws java.lang.Exception

get the final selected set of attributes.

Returns:

an array of attribute indexes

Throws:

java.lang.Exception - if attribute selection has not been performed yet

rankedAttributes

public double[][] rankedAttributes()
                            throws java.lang.Exception

get the final ranking of the attributes.

Returns:

a two dimensional array of ranked attribute indexes and their associated merit scores as doubles.

Throws:

java.lang.Exception - if a ranking has not been produced

setEvaluator

public void setEvaluator(ASEvaluation evaluator)

set the attribute/subset evaluator

Parameters:

evaluator - the evaluator to use

setSearch

public void setSearch(ASSearch search)

set the search method

Parameters:

search - the search method to use

setFolds

public void setFolds(int folds)

set the number of folds for cross validation

Parameters:

folds - the number of folds

setRanking

public void setRanking(boolean r)

produce a ranking (if possible with the set search and evaluator)

Parameters:

r - true if a ranking is to be produced

setXval

public void setXval(boolean x)

do a cross validation

Parameters:

x - true if a cross validation is to be performed

setSeed

public void setSeed(int s)

set the seed for use in cross validation

Parameters:

s - the seed

setThreshold

public void setThreshold(double t)

set the threshold by which to select features from a ranked list

Parameters:

t - the threshold

toResultsString

public java.lang.String toResultsString()

get a description of the attribute selection

Returns:

a String describing the results of attribute selection

reduceDimensionality

public Instances reduceDimensionality(Instances in)
                               throws java.lang.Exception

reduce the dimensionality of a set of instances to include only those attributes chosen by the last run of attribute selection.

Parameters:

in - the instances to be reduced

Returns:

a dimensionality reduced set of instances

Throws:

java.lang.Exception - if the instances can't be reduced

reduceDimensionality

public Instance reduceDimensionality(Instance in)
                              throws java.lang.Exception

reduce the dimensionality of a single instance to include only those attributes chosen by the last run of attribute selection.

Parameters:

in - the instance to be reduced

Returns:

a dimensionality reduced instance

Throws:

java.lang.Exception - if the instance can't be reduced

SelectAttributes

public static java.lang.String SelectAttributes(ASEvaluation ASEvaluator,
                                                java.lang.String[] options)
                                         throws java.lang.Exception

Perform attribute selection with a particular evaluator and a set of options specifying search method and input file etc.

Parameters:

ASEvaluator - an evaluator object

options - an array of options, not only for the evaluator but also the search method (if any) and an input data file

Returns:

the results of attribute selection as a String

Throws:

java.lang.Exception - if no training file is set

CVResultsString

public java.lang.String CVResultsString()
                                 throws java.lang.Exception

returns a string summarizing the results of repeated attribute selection runs on splits of a dataset.

Returns:

a summary of attribute selection results

Throws:

java.lang.Exception - if no attribute selection has been performed.

selectAttributesCVSplit

public void selectAttributesCVSplit(Instances split)
                             throws java.lang.Exception

Select attributes for a split of the data. Calling this function updates the statistics on attribute selection. CVResultsString() returns a string summarizing the results of repeated calls to this function. Assumes that splits are from the same dataset--- ie. have the same number and types of attributes as previous splits.

Parameters:

split - the instances to select attributes from

Throws:

java.lang.Exception - if an error occurs

CrossValidateAttributes

public java.lang.String CrossValidateAttributes()
                                         throws java.lang.Exception

Perform a cross validation for attribute selection. With subset evaluators the number of times each attribute is selected over the cross validation is reported. For attribute evaluators, the average merit and average ranking + std deviation is reported for each attribute.

Returns:

the results of cross validation as a String

Throws:

java.lang.Exception - if an error occurs during cross validation

SelectAttributes

public void SelectAttributes(Instances data)
                      throws java.lang.Exception

Perform attribute selection on the supplied training instances.

Parameters:

data - the instances to select attributes from

Throws:

java.lang.Exception - if there is a problem during selection

SelectAttributes

public static java.lang.String SelectAttributes(ASEvaluation ASEvaluator,
                                                java.lang.String[] options,
                                                Instances train)
                                         throws java.lang.Exception

Perform attribute selection with a particular evaluator and a set of options specifying search method and options for the search method and evaluator.

Parameters:

ASEvaluator - an evaluator object

options - an array of options, not only for the evaluator but also the search method (if any) and an input data file

train - the input instances

Returns:

the results of attribute selection as a String

Throws:

java.lang.Exception - if incorrect options are supplied

main

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

Main method for testing this class.

Parameters:

args - the options