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## weka.filters.unsupervised.attribute
Class RemoveUseless

    java.lang.Object
      weka.filters.Filter
          weka.filters.unsupervised.attribute.RemoveUseless

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

    public class RemoveUseless

extends Filter
implements UnsupervisedFilter, OptionHandler

This filter removes attributes that do not vary at all or that vary too much. All constant attributes are deleted automatically, along with any that exceed the maximum percentage of variance parameter. The maximum variance test is only applied to nominal attributes.

Valid filter-specific options are:

-M percentage
The maximum variance allowed before an attribute will be deleted (default 99).

Version:
  $Revision: 1.5 $
Author:
  Richard Kirkby (rkirkby@cs.waikato.ac.nz)
See Also:
  Serialized Form

Constructor Summary
`RemoveUseless()`

Method Summary
`boolean` | `batchFinished()` Signify that this batch of input to the filter is finished.
`double` | `getMaximumVariancePercentageAllowed()` Gets the maximum variance attributes are allowed to have before they are deleted by the filter.
`java.lang.String[]` | `getOptions()` Gets the current settings of the filter.
`java.lang.String` | `globalInfo()` Returns a string describing this filter
`boolean` | `input(Instance instance)` Input an instance for filtering.
`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` | `maximumVariancePercentageAllowedTipText()` Returns the tip text for this property
`boolean` | `setInputFormat(Instances instanceInfo)` Sets the format of the input instances.
`void` | `setMaximumVariancePercentageAllowed(double maxVariance)` Sets the maximum variance attributes are allowed to have before they are deleted by the filter.
`void` | `setOptions(java.lang.String[] options)` Parses the options for this object.

Methods inherited from class weka.filters.Filter
`batchFilterFile, filterFile, getOutputFormat, inputFormat, isOutputFormatDefined, numPendingOutput, output, outputFormat, outputPeek, useFilter`

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

Constructor Detail

### RemoveUseless

    public RemoveUseless()

Method Detail

### 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 may be collected immediately
  Throws:
    `java.lang.Exception` - if the inputFormat can't be set successfully

### input

    public boolean input(Instance instance)

  Input an instance for filtering.

  Overrides:
    `input` in class `Filter`
  Parameters:
    `instance` - the input instance
  Returns:
    true if the filtered instance may now be collected with output().

### batchFinished

    public boolean batchFinished()
                          throws java.lang.Exception

  Signify that this batch of input to the filter is finished.

  Overrides:
    `batchFinished` in class `Filter`
  Returns:
    true if there are instances pending output
  Throws:
    `java.lang.NullPointerException` - if no input structure has been defined,
    `java.lang.Exception` - if there was a problem finishing the batch.

### 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 the options for this object. Valid options are:

  -M percentage
  The maximum variance allowed before an attribute will be deleted (default 99).

  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

### globalInfo

    public java.lang.String globalInfo()

  Returns a string describing this filter

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

### maximumVariancePercentageAllowedTipText

    public java.lang.String maximumVariancePercentageAllowedTipText()

  Returns the tip text for this property

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

### setMaximumVariancePercentageAllowed

    public void setMaximumVariancePercentageAllowed(double maxVariance)

  Sets the maximum variance attributes are allowed to have before they are deleted by the filter.

  Parameters:
    `maxVariance` - the maximum variance allowed, specified as a percentage

### getMaximumVariancePercentageAllowed

    public double getMaximumVariancePercentageAllowed()

  Gets the maximum variance attributes are allowed to have before they are deleted by the filter.

  Returns:
    the maximum variance allowed, specified as a percentage

### 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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