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## weka.attributeSelection
Class Ranker

    java.lang.Object
      weka.attributeSelection.ASSearch
          weka.attributeSelection.Ranker

All Implemented Interfaces:
  java.io.Serializable, RankedOutputSearch, StartSetHandler, OptionHandler, RevisionHandler

    public class Ranker

extends ASSearch
implements RankedOutputSearch, StartSetHandler, OptionHandler

Ranker :
Ranks attributes by their individual evaluations. Use in conjunction with attribute evaluators (ReliefF, GainRatio, Entropy etc).

Valid options are:

     -P <start set>
      Specify a starting set of attributes.
      Eg. 1,3,5-7.
      Any starting attributes specified are
      ignored during the ranking.

     -T <threshold>
      Specify a theshold by which attributes
      may be discarded from the ranking.

     -N <num to select>
      Specify number of attributes to select

Version:
  $Revision: 1.26 $
Author:
  Mark Hall (mhall@cs.waikato.ac.nz)
See Also:
  Serialized Form

Constructor Summary
`Ranker()` Constructor

Method Summary
`java.lang.String` | `generateRankingTipText()` Returns the tip text for this property
`int` | `getCalculatedNumToSelect()` Gets the calculated number to select.
`boolean` | `getGenerateRanking()` This is a dummy method.
`int` | `getNumToSelect()` Gets the number of attributes to be retained.
`java.lang.String[]` | `getOptions()` Gets the current settings of ReliefFAttributeEval.
`java.lang.String` | `getRevision()` Returns the revision string.
`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()` Sorts the evaluated attribute list
`int[]` | `search(ASEvaluation ASEval, Instances data)` Kind of a dummy search algorithm.
`void` | `setGenerateRanking(boolean doRank)` This is a dummy set method---Ranker is ONLY capable of producing a ranked list of attributes for attribute evaluators.
`void` | `setNumToSelect(int n)` Specify the number of attributes to select from the ranked list.
`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 as a String

Methods inherited from class weka.attributeSelection.ASSearch
`forName, makeCopies`

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

### Ranker

    public Ranker()

  Constructor

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

### 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. -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 to select. This might be computed from a threshold, or if < 0 is set as the number to select then it is set to the number of attributes in the (transformed) data.

  Specified by:
    `getCalculatedNumToSelect` in interface `RankedOutputSearch`
  Returns:
    the calculated number of attributes to select

### 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

### 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)

  This is a dummy set method---Ranker is ONLY capable of producing a ranked list of attributes for attribute evaluators.

  Specified by:
    `setGenerateRanking` in interface `RankedOutputSearch`
  Parameters:
    `doRank` - this parameter is N/A and is ignored

### getGenerateRanking

    public boolean getGenerateRanking()

  This is a dummy method. Ranker can ONLY be used with attribute evaluators and as such can only produce a ranked list of attributes

  Specified by:
    `getGenerateRanking` in interface `RankedOutputSearch`
  Returns:
    true all the time.

### 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 <start set>
        Specify a starting set of attributes.
        Eg. 1,3,5-7.
        Any starting attributes specified are
        ignored during the ranking.

       -T <threshold>
        Specify a theshold by which attributes
        may be discarded from the ranking.

       -N <num to select>
        Specify number of attributes to select

  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()

### search

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

  Kind of a dummy search algorithm. Calls a Attribute evaluator to evaluate each attribute not included in the startSet and then sorts them to produce a ranked list of attributes.

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

### rankedAttributes

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

  Sorts the evaluated attribute list

  Specified by:
    `rankedAttributes` in interface `RankedOutputSearch`
  Returns:
    an array of sorted (highest eval to lowest) attribute indexes
  Throws:
    `java.lang.Exception` - of sorting can't be done.

### toString

    public java.lang.String toString()

  returns a description of the search as a String

  Overrides:
    `toString` in class `java.lang.Object`
  Returns:
    a description of the search

### getRevision

    public java.lang.String getRevision()

  Returns the revision string.

  Specified by:
    `getRevision` in interface `RevisionHandler`
  Overrides:
    `getRevision` in class `ASSearch`
  Returns:
    the revision

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