Package weka.attributeSelection

Class GreedyStepwise

java.lang.Object
weka.attributeSelection.ASSearch
weka.attributeSelection.GreedyStepwise
All Implemented Interfaces:
Serializable, RankedOutputSearch, StartSetHandler, OptionHandler, RevisionHandler
public class GreedyStepwise extends ASSearch implements RankedOutputSearch, StartSetHandler, OptionHandler
GreedyStepwise :

Performs a greedy forward or backward search through the space of attribute subsets. May start with no/all attributes or from an arbitrary point in the space. Stops when the addition/deletion of any remaining attributes results in a decrease in evaluation. Can also produce a ranked list of attributes by traversing the space from one side to the other and recording the order that attributes are selected.

Valid options are: 

 -C
  Use conservative forward search
 
 -B
  Use a backward search instead of a
  forward one.
 
 -P <start set>
  Specify a starting set of attributes.
  Eg. 1,3,5-7.
 
 -R
  Produce a ranked list of attributes.
 
 -T <threshold>
  Specify a theshold by which attributes
  may be discarded from the ranking.
  Use in conjuction with -R
 
 -N <num to select>
  Specify number of attributes to select
 
 -num-slots <int>
  The number of execution slots, for example, the number of cores in the CPU. (default 1)
 
 -D
  Print debugging output
Version:
$Revision: 15519 $
Author:
Mark Hall
See Also:

  • Constructor Details

    • GreedyStepwise

      public GreedyStepwise()
      Constructor

  • Method Details

    • globalInfo

      public String globalInfo()
      Returns a string describing this search method
      Returns:
      a description of the search suitable for displaying in the explorer/experimenter gui

    • searchBackwardsTipText

      public String searchBackwardsTipText()
      Returns the tip text for this property
      Returns:
      tip text for this property suitable for displaying in the explorer/experimenter gui

    • setSearchBackwards

      public void setSearchBackwards(boolean back)
      Set whether to search backwards instead of forwards
      Parameters:
      back - true to search backwards

    • getSearchBackwards

      public boolean getSearchBackwards()
      Get whether to search backwards
      Returns:
      true if the search will proceed backwards

    • thresholdTipText

      public 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 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 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 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(String startSet) throws 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:
      Exception - if start set can't be set.

    • getStartSet

      public 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)

    • conservativeForwardSelectionTipText

      public String conservativeForwardSelectionTipText()
      Returns the tip text for this property
      Returns:
      tip text for this property suitable for displaying in the explorer/experimenter gui

    • setConservativeForwardSelection

      public void setConservativeForwardSelection(boolean c)
      Set whether attributes should continue to be added during a forward search as long as merit does not decrease
      Parameters:
      c - true if atts should continue to be atted

    • getConservativeForwardSelection

      public boolean getConservativeForwardSelection()
      Gets whether conservative selection has been enabled
      Returns:
      true if conservative forward selection is enabled

    • debuggingOutputTipText

      public String debuggingOutputTipText()
      Returns the tip text for this property
      Returns:
      tip text for this property suitable for displaying in the explorer/experimenter gui

    • setDebuggingOutput

      public void setDebuggingOutput(boolean d)
      Set whether to output debugging info to the console
      Parameters:
      d - true if dubugging info is to be output

    • getDebuggingOutput

      public boolean getDebuggingOutput()
      Get whether to output debugging info to the console
      Returns:
      true if dubugging info is to be output

    • numExecutionSlotsTipText

      public String numExecutionSlotsTipText()
      Returns:
      a string to describe the option

    • getNumExecutionSlots

      public int getNumExecutionSlots()
      Gets the number of threads.

    • setNumExecutionSlots

      public void setNumExecutionSlots(int nT)
      Sets the number of threads

    • listOptions

      public Enumeration<Option> listOptions()
      Returns an enumeration describing the available options.
      Specified by:
      listOptions in interface OptionHandler
      Overrides:
      listOptions in class ASSearch
      Returns:
      an enumeration of all the available options.

    • setOptions

      public void setOptions(String[] options) throws Exception
      Parses a given list of options.

      Valid options are: 

       -C
  Use conservative forward search
 
       -B
  Use a backward search instead of a
  forward one.
 
       -P <start set>
  Specify a starting set of attributes.
  Eg. 1,3,5-7.
 
       -R
  Produce a ranked list of attributes.
 
       -T <threshold>
  Specify a theshold by which attributes
  may be discarded from the ranking.
  Use in conjuction with -R
 
       -N <num to select>
  Specify number of attributes to select
 
       -num-slots <int>
  The number of execution slots, for example, the number of cores in the CPU. (default 1)
 
       -D
  Print debugging output
      Specified by:
      setOptions in interface OptionHandler
      Overrides:
      setOptions in class ASSearch
      Parameters:
      options - the list of options as an array of strings
      Throws:
      Exception - if an option is not supported

    • getOptions

      public String[] getOptions()
      Gets the current settings of ReliefFAttributeEval.
      Specified by:
      getOptions in interface OptionHandler
      Overrides:
      getOptions in class ASSearch
      Returns:
      an array of strings suitable for passing to setOptions()

    • toString

      public String toString()
      returns a description of the search.
      Overrides:
      toString in class Object
      Returns:
      a description of the search as a String.

    • search

      public int[] search(ASEvaluation ASEval, Instances data) throws Exception
      Searches the attribute subset space by forward selection.
      Specified by:
      search in class ASSearch
      Parameters:
      ASEval - the attribute evaluator to guide the search
      data - the training instances.
      Returns:
      an array (not necessarily ordered) of selected attribute indexes
      Throws:
      Exception - if the search can't be completed

    • rankedAttributes

      public double[][] rankedAttributes() throws 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:
      Exception - if something goes wrong.

    • getRevision

      public String getRevision()
      Returns the revision string.
      Specified by:
      getRevision in interface RevisionHandler
      Overrides:
      getRevision in class ASSearch
      Returns:
      the revision