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## weka.filters.unsupervised.instance
Class RemoveFrequentValues

    java.lang.Object
      weka.filters.Filter
          weka.filters.unsupervised.instance.RemoveFrequentValues

All Implemented Interfaces:
  java.io.Serializable, CapabilitiesHandler, OptionHandler, RevisionHandler, UnsupervisedFilter

    public class RemoveFrequentValues

extends Filter
implements OptionHandler, UnsupervisedFilter

Determines which values (frequent or infrequent ones) of an (nominal) attribute are retained and filters the instances accordingly. In case of values with the same frequency, they are kept in the way they appear in the original instances object. E.g. if you have the values "1,2,3,4" with the frequencies "10,5,5,3" and you chose to keep the 2 most common values, the values "1,2" would be returned, since the value "2" comes before "3", even though they have the same frequency.

Valid options are:

     -C <num>
      Choose attribute to be used for selection.

     -N <num>
      Number of values to retain for the sepcified attribute,
      i.e. the ones with the most instances (default 2).

     -L
      Instead of values with the most instances the ones with the
      least are retained.

     -H
      When selecting on nominal attributes, removes header
      references to excluded values.

     -V
      Invert matching sense.

Version:
  $Revision: 8590 $
Author:
  FracPete (fracpete at waikato dot ac dot nz)
See Also:
  Serialized Form

Constructor Summary
`RemoveFrequentValues()`

Method Summary
`java.lang.String` | `attributeIndexTipText()` Returns the tip text for this property
`boolean` | `batchFinished()` Signifies that this batch of input to the filter is finished.
`void` | `determineValues(Instances inst)` determines the values to retain, it is always at least 1 and up to the maximum number of distinct values
`java.lang.String` | `getAttributeIndex()` Get the index of the attribute used.
`Capabilities` | `getCapabilities()` Returns the Capabilities of this filter.
`boolean` | `getInvertSelection()` Get whether the supplied columns are to be removed or kept
`boolean` | `getModifyHeader()` Gets whether the header will be modified when selecting on nominal attributes.
`int` | `getNumValues()` Gets how many values are retained
`java.lang.String[]` | `getOptions()` Gets the current settings of the filter.
`java.lang.String` | `getRevision()` Returns the revision string.
`boolean` | `getUseLeastValues()` Gets whether to use values with least or most instances
`java.lang.String` | `globalInfo()` Returns a string describing this filter
`boolean` | `input(Instance instance)` Input an instance for filtering.
`java.lang.String` | `invertSelectionTipText()` Returns the tip text for this property
`boolean` | `isNominal()` Returns true if selection attribute is nominal.
`java.util.Enumeration` | `listOptions()` Returns an enumeration describing the available options.
`static void` | `main(java.lang.String[] argv)` Main method for testing this class.
`java.lang.String` | `modifyHeaderTipText()` Returns the tip text for this property
`java.lang.String` | `numValuesTipText()` Returns the tip text for this property
`void` | `setAttributeIndex(java.lang.String attIndex)` Sets index of the attribute used.
`boolean` | `setInputFormat(Instances instanceInfo)` Sets the format of the input instances.
`void` | `setInvertSelection(boolean invert)` Set whether selected values should be removed or kept.
`void` | `setModifyHeader(boolean newModifyHeader)` Sets whether the header will be modified when selecting on nominal attributes.
`void` | `setNumValues(int numValues)` Sets how many values are retained
`void` | `setOptions(java.lang.String[] options)` Parses a given list of options.
`void` | `setUseLeastValues(boolean leastValues)` Sets whether to use values with least or most instances
`java.lang.String` | `useLeastValuesTipText()` Returns the tip text for this property

Methods inherited from class weka.filters.Filter
`batchFilterFile, filterFile, getCapabilities, getOutputFormat, isFirstBatchDone, isNewBatch, isOutputFormatDefined, makeCopies, makeCopy, numPendingOutput, output, outputPeek, toString, useFilter, wekaStaticWrapper`

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

Constructor Detail

### RemoveFrequentValues

    public RemoveFrequentValues()

Method Detail

### globalInfo

    public java.lang.String globalInfo()

  Returns a string describing this filter

  Returns:
    a description of the classifier suitable for displaying in the explorer/experimenter gui

### 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:

       -C <num>
        Choose attribute to be used for selection.

       -N <num>
        Number of values to retain for the sepcified attribute,
        i.e. the ones with the most instances (default 2).

       -L
        Instead of values with the most instances the ones with the
        least are retained.

       -H
        When selecting on nominal attributes, removes header
        references to excluded values.

       -V
        Invert matching sense.

  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 the filter.

  Specified by:
    `getOptions` in interface `OptionHandler`
  Returns:
    an array of strings suitable for passing to setOptions

### attributeIndexTipText

    public java.lang.String attributeIndexTipText()

  Returns the tip text for this property

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

### getAttributeIndex

    public java.lang.String getAttributeIndex()

  Get the index of the attribute used.

  Returns:
    the index of the attribute

### setAttributeIndex

    public void setAttributeIndex(java.lang.String attIndex)

  Sets index of the attribute used.

  Parameters:
    `attIndex` - the index of the attribute

### numValuesTipText

    public java.lang.String numValuesTipText()

  Returns the tip text for this property

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

### getNumValues

    public int getNumValues()

  Gets how many values are retained

  Returns:
    how many values are retained

### setNumValues

    public void setNumValues(int numValues)

  Sets how many values are retained

  Parameters:
    `numValues` - the number of values to retain

### useLeastValuesTipText

    public java.lang.String useLeastValuesTipText()

  Returns the tip text for this property

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

### getUseLeastValues

    public boolean getUseLeastValues()

  Gets whether to use values with least or most instances

  Returns:
    true if values with least instances are retained

### setUseLeastValues

    public void setUseLeastValues(boolean leastValues)

  Sets whether to use values with least or most instances

  Parameters:
    `leastValues` - whether values with least or most instances are retained

### modifyHeaderTipText

    public java.lang.String modifyHeaderTipText()

  Returns the tip text for this property

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

### getModifyHeader

    public boolean getModifyHeader()

  Gets whether the header will be modified when selecting on nominal attributes.

  Returns:
    true if so.

### setModifyHeader

    public void setModifyHeader(boolean newModifyHeader)

  Sets whether the header will be modified when selecting on nominal attributes.

  Parameters:
    `newModifyHeader` - true if so.

### invertSelectionTipText

    public java.lang.String invertSelectionTipText()

  Returns the tip text for this property

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

### getInvertSelection

    public boolean getInvertSelection()

  Get whether the supplied columns are to be removed or kept

  Returns:
    true if the supplied columns will be kept

### setInvertSelection

    public void setInvertSelection(boolean invert)

  Set whether selected values should be removed or kept. If true the selected values are kept and unselected values are deleted.

  Parameters:
    `invert` - the new invert setting

### isNominal

    public boolean isNominal()

  Returns true if selection attribute is nominal.

  Returns:
    true if selection attribute is nominal

### determineValues

    public void determineValues(Instances inst)

  determines the values to retain, it is always at least 1 and up to the maximum number of distinct values

  Parameters:
    `inst` - the Instances to determine the values from which are kept

### getCapabilities

    public Capabilities getCapabilities()

  Returns the Capabilities of this filter.

  Specified by:
    `getCapabilities` in interface `CapabilitiesHandler`
  Overrides:
    `getCapabilities` in class `Filter`
  Returns:
    the capabilities of this object
  See Also:
    `Capabilities`

### setInputFormat

    public boolean setInputFormat(Instances instanceInfo)
                           throws java.lang.Exception

  Sets the format of the input instances.

  Overrides:
    `setInputFormat` in class `Filter`
  Parameters:
    `instanceInfo` - an Instances object containing the input instance structure (any instances contained in the object are ignored - only the structure is required).
  Returns:
    true if the outputFormat can be collected immediately
  Throws:
    `UnsupportedAttributeTypeException` - if the specified attribute is not nominal.
    `java.lang.Exception` - if the inputFormat can't be set successfully

### input

    public boolean input(Instance instance)

  Input an instance for filtering. Ordinarily the instance is processed and made available for output immediately. Some filters require all instances be read before producing output.

  Overrides:
    `input` in class `Filter`
  Parameters:
    `instance` - the input instance
  Returns:
    true if the filtered instance may now be collected with output().
  Throws:
    `java.lang.IllegalStateException` - if no input format has been set.

### batchFinished

    public boolean batchFinished()

  Signifies that this batch of input to the filter is finished. If the filter requires all instances prior to filtering, output() may now be called to retrieve the filtered instances.

  Overrides:
    `batchFinished` in class `Filter`
  Returns:
    true if there are instances pending output
  Throws:
    `java.lang.IllegalStateException` - if no input structure has been defined

### getRevision

    public java.lang.String getRevision()

  Returns the revision string.

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

### main

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

  Main method for testing this class.

  Parameters:
    `argv` - should contain arguments to the filter: use -h for help

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