weka.attributeSelection
Class ForwardSelection

java.lang.Object
  |
  +--weka.attributeSelection.ASSearch
        |
        +--weka.attributeSelection.ForwardSelection

All Implemented Interfaces:

OptionHandler, RankedOutputSearch, java.io.Serializable, StartSetHandler

public class ForwardSelection

extends ASSearch

implements RankedOutputSearch, StartSetHandler, OptionHandler

Class for performing a forward selection hill climbing search.

Valid options are:

-P
Specify a starting set of attributes. Eg 1,4,7-9.

-R
Produce a ranked list of attributes.

-T
Specify a threshold by which the AttributeSelection module can.
discard attributes. Use in conjunction with -R

Version:

$Revision: 1.15 $

Author:

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

See Also:

Serialized Form

Constructor Summary

ForwardSelection()

Method Summary

java.lang.String	generateRankingTipText() Returns the tip text for this property
int	getCalculatedNumToSelect() Gets the calculated number of attributes to retain.
boolean	getGenerateRanking() Gets whether ranking has been requested.
int	getNumToSelect() Gets the number of attributes to be retained.
java.lang.String[]	getOptions() Gets the current settings of ReliefFAttributeEval.
java.lang.String	getStartSet() Returns a list of attributes (and or attribute ranges) as a String
double	getThreshold() Returns the threshold so that the AttributeSelection module can discard attributes from the ranking.
java.lang.String	globalInfo() Returns a string describing this search method
java.util.Enumeration	listOptions() Returns an enumeration describing the available options.
java.lang.String	numToSelectTipText() Returns the tip text for this property
double[][]	rankedAttributes() Produces a ranked list of attributes.
int[]	search(ASEvaluation ASEval, Instances data) Searches the attribute subset space by forward selection.
void	setGenerateRanking(boolean doRank) Records whether the user has requested a ranked list of attributes.
void	setNumToSelect(int n) Specify the number of attributes to select from the ranked list (if generating a ranking).
void	setOptions(java.lang.String[] options) Parses a given list of options.
void	setStartSet(java.lang.String startSet) Sets a starting set of attributes for the search.
void	setThreshold(double threshold) Set the threshold by which the AttributeSelection module can discard attributes.
java.lang.String	startSetTipText() Returns the tip text for this property
java.lang.String	thresholdTipText() Returns the tip text for this property
java.lang.String	toString() returns a description of the search.

Methods inherited from class weka.attributeSelection.ASSearch

forName

Methods inherited from class java.lang.Object

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

Constructor Detail

ForwardSelection

public ForwardSelection()

Method Detail

globalInfo

public java.lang.String globalInfo()

Returns a string describing this search method

Returns:

a description of the search suitable for displaying in the explorer/experimenter gui

thresholdTipText

public java.lang.String thresholdTipText()

Returns the tip text for this property

Returns:

tip text for this property suitable for displaying in the explorer/experimenter gui

setThreshold

public void setThreshold(double threshold)

Set the threshold by which the AttributeSelection module can discard attributes.

Specified by:

setThreshold in interface RankedOutputSearch

Parameters:

threshold - the threshold.

getThreshold

public double getThreshold()

Returns the threshold so that the AttributeSelection module can discard attributes from the ranking.

Specified by:

getThreshold in interface RankedOutputSearch

Returns:

a threshold by which to discard attributes

numToSelectTipText

public java.lang.String numToSelectTipText()

Returns the tip text for this property

Returns:

tip text for this property suitable for displaying in the explorer/experimenter gui

setNumToSelect

public void setNumToSelect(int n)

Specify the number of attributes to select from the ranked list (if generating a ranking). -1 indicates that all attributes are to be retained.

Specified by:

setNumToSelect in interface RankedOutputSearch

Parameters:

n - the number of attributes to retain

getNumToSelect

public int getNumToSelect()

Gets the number of attributes to be retained.

Specified by:

getNumToSelect in interface RankedOutputSearch

Returns:

the number of attributes to retain

getCalculatedNumToSelect

public int getCalculatedNumToSelect()

Gets the calculated number of attributes to retain. This is the actual number of attributes to retain. This is the same as getNumToSelect if the user specifies a number which is not less than zero. Otherwise it should be the number of attributes in the (potentially transformed) data.

Specified by:

getCalculatedNumToSelect in interface RankedOutputSearch

generateRankingTipText

public java.lang.String generateRankingTipText()

Returns the tip text for this property

Returns:

tip text for this property suitable for displaying in the explorer/experimenter gui

setGenerateRanking

public void setGenerateRanking(boolean doRank)

Records whether the user has requested a ranked list of attributes.

Specified by:

setGenerateRanking in interface RankedOutputSearch

Parameters:

doRank - true if ranking is requested

getGenerateRanking

public boolean getGenerateRanking()

Gets whether ranking has been requested. This is used by the AttributeSelection module to determine if rankedAttributes() should be called.

Specified by:

getGenerateRanking in interface RankedOutputSearch

Returns:

true if ranking has been requested.

startSetTipText

public java.lang.String startSetTipText()

Returns the tip text for this property

Returns:

tip text for this property suitable for displaying in the explorer/experimenter gui

setStartSet

public void setStartSet(java.lang.String startSet)
                 throws java.lang.Exception

Sets a starting set of attributes for the search. It is the search method's responsibility to report this start set (if any) in its toString() method.

Specified by:

setStartSet in interface StartSetHandler

Parameters:

startSet - a string containing a list of attributes (and or ranges), eg. 1,2,6,10-15.

Throws:

java.lang.Exception - if start set can't be set.

getStartSet

public java.lang.String getStartSet()

Returns a list of attributes (and or attribute ranges) as a String

Specified by:

getStartSet in interface StartSetHandler

Returns:

a list of attributes (and or attribute ranges)

listOptions

public java.util.Enumeration listOptions()

Returns an enumeration describing the available options.

Specified by:

listOptions in interface OptionHandler

Returns:

an enumeration of all the available options.

setOptions

public void setOptions(java.lang.String[] options)
                throws java.lang.Exception

Parses a given list of options. Valid options are:

-P
Specify a starting set of attributes. Eg 1,4,7-9.

-R
Produce a ranked list of attributes.

-T
Specify a threshold by which the AttributeSelection module can
discard attributes. Use in conjunction with -R

-N
Specify the number of attributes to retain. Overides any threshold.

Specified by:

setOptions in interface OptionHandler

Parameters:

options - the list of options as an array of strings

Throws:

java.lang.Exception - if an option is not supported

getOptions

public java.lang.String[] getOptions()

Gets the current settings of ReliefFAttributeEval.

Specified by:

getOptions in interface OptionHandler

Returns:

an array of strings suitable for passing to setOptions()

toString

public java.lang.String toString()

returns a description of the search.

Overrides:

toString in class java.lang.Object

Returns:

a description of the search as a String.

search

public int[] search(ASEvaluation ASEval,
                    Instances data)
             throws java.lang.Exception

Searches the attribute subset space by forward selection.

Specified by:

search in class ASSearch

Parameters:

data - the training instances.

ASEval - the attribute evaluator to guide the search

Returns:

an array (not necessarily ordered) of selected attribute indexes

Throws:

java.lang.Exception - if the search can't be completed

rankedAttributes

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

Produces a ranked list of attributes. Search must have been performed prior to calling this function. Search is called by this function to complete the traversal of the the search space. A list of attributes and merits are returned. The attributes a ranked by the order they are added to the subset during a forward selection search. Individual merit values reflect the merit associated with adding the corresponding attribute to the subset; because of this, merit values may initially increase but then decrease as the best subset is "passed by" on the way to the far side of the search space.

Specified by:

rankedAttributes in interface RankedOutputSearch

Returns:

an array of attribute indexes and associated merit values

Throws:

java.lang.Exception - if something goes wrong.