Package weka.attributeSelection

Class AttributeSelection

  • All Implemented Interfaces:
    Serializable, RevisionHandler
    public class AttributeSelection
extends Object
implements Serializable, RevisionHandler
    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 <name of input file>
    Specify the training data file.

    -c <class index>
    The index of the attribute to use as the class.

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

    -x <number of folds>
    Perform a cross validation.

    -n <random number seed>
    Specify a random number seed. Use in conjuction with -x. (Default = 1).

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

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

     public static void main(String[] args) {
   runEvaluator(new FunkyEvaluator(), args);
 }

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

    Version:
    $Revision$
    Author:
    Mark Hall (mhall@cs.waikato.ac.nz)
    See Also:
    Serialized Form

    • 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 Exception
        Return the number of attributes selected from the most recent run of attribute selection
        Returns:
        the number of attributes selected
        Throws:
        Exception

      • selectedAttributes

        public int[] selectedAttributes()
                         throws Exception
        get the final selected set of attributes.
        Returns:
        an array of attribute indexes
        Throws:
        Exception - if attribute selection has not been performed yet

      • rankedAttributes

        public double[][] rankedAttributes()
                            throws 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:
        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

      • toResultsString

        public 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 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:
        Exception - if the instances can't be reduced

      • reduceDimensionality

        public Instance reduceDimensionality​(Instance in)
                              throws 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:
        Exception - if the instance can't be reduced

      • SelectAttributes

        public static String SelectAttributes​(ASEvaluation ASEvaluator,
                                      String[] options)
                               throws 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:
        Exception - if no training file is set

      • CVResultsString

        public String CVResultsString()
                       throws 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:
        Exception - if no attribute selection has been performed.

      • selectAttributesCVSplit

        public void selectAttributesCVSplit​(Instances split)
                             throws 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:
        Exception - if an error occurs

      • updateStatsForModelCVSplit

        public void updateStatsForModelCVSplit​(Instances split,
                                       ASEvaluation evaluator,
                                       ASSearch search,
                                       int[] attributeSet,
                                       boolean doRank)
                                throws Exception
        Update the attribute selection stats for a cross-validation fold of the data.
        Parameters:
        split - the instances in this split/fold of the data
        evaluator - the evaluator that was used
        search - the search that was used
        attributeSet - the final subset produced for the split
        doRank - whether to produce a ranking
        Throws:
        Exception - if a problem occurs

      • CrossValidateAttributes

        public String CrossValidateAttributes()
                               throws 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:
        Exception - if an error occurs during cross validation

      • SelectAttributes

        public void SelectAttributes​(Instances data)
                      throws Exception
        Perform attribute selection on the supplied training instances.
        Parameters:
        data - the instances to select attributes from
        Throws:
        Exception - if there is a problem during selection

      • SelectAttributes

        public static String SelectAttributes​(ASEvaluation ASEvaluator,
                                      String[] options,
                                      Instances train)
                               throws 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:
        Exception - if incorrect options are supplied

      • main

        public static void main​(String[] args)
        Main method for testing this class.
        Parameters:
        args - the options