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## weka.filters.unsupervised.instance
Class SubsetByExpression

    java.lang.Object
      weka.filters.Filter
          weka.filters.SimpleFilter
              weka.filters.SimpleBatchFilter
                  weka.filters.unsupervised.instance.SubsetByExpression

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

    public class SubsetByExpression

extends SimpleBatchFilter

Filters instances according to a user-specified expression.
Grammar:
boolexpr_list ::= boolexpr_list boolexpr_part | boolexpr_part;
boolexpr_part ::= boolexpr:e {: parser.setResult(e); :} ;
boolexpr ::= BOOLEAN
| true
| false
| expr < expr
| expr <= expr
| expr > expr
| expr >= expr
| expr = expr
| ( boolexpr )
| not boolexpr
| boolexpr and boolexpr
| boolexpr or boolexpr
| ATTRIBUTE is STRING
;
expr ::= NUMBER
| ATTRIBUTE
| ( expr )
| opexpr
| funcexpr
;
opexpr ::= expr + expr
| expr - expr
| expr * expr
| expr / expr
;
funcexpr ::= abs ( expr )
| sqrt ( expr )
| log ( expr )
| exp ( expr )
| sin ( expr )
| cos ( expr )
| tan ( expr )
| rint ( expr )
| floor ( expr )
| pow ( expr for base , expr for exponent )
| ceil ( expr )
;
Notes:
- NUMBER
any integer or floating point number
(but not in scientific notation!)
- STRING
any string surrounded by single quotes;
the string may not contain a single quote though.
- ATTRIBUTE
the following placeholders are recognized for
attribute values:
- CLASS for the class value in case a class attribute is set.
- ATTxyz with xyz a number from 1 to # of attributes in the
dataset, representing the value of indexed attribute.
Examples:
- extracting only mammals and birds from the 'zoo' UCI dataset:
(CLASS is 'mammal') or (CLASS is 'bird')
- extracting only animals with at least 2 legs from the 'zoo' UCI dataset:
(ATT14 >= 2)
- extracting only instances with non-missing 'wage-increase-second-year'
from the 'labor' UCI dataset:
not ismissing(ATT3)

Valid options are:

     -E <expr>
      The expression to use for filtering
      (default: true).

Version:
  $Revision: 6113 $
Author:
  fracpete (fracpete at waikato dot ac dot nz)
See Also:
  Serialized Form

Constructor Summary
`SubsetByExpression()`

Method Summary
`java.lang.String` | `expressionTipText()` Returns the tip text for this property.
`Capabilities` | `getCapabilities()` Returns the Capabilities of this filter.
`java.lang.String` | `getExpression()` Returns the expression used for filtering.
`java.lang.String[]` | `getOptions()` Gets the current settings of the filter.
`java.lang.String` | `getRevision()` Returns the revision string.
`java.lang.String` | `globalInfo()` Returns a string describing this filter.
`java.util.Enumeration` | `listOptions()` Returns an enumeration describing the available options.
`static void` | `main(java.lang.String[] args)` Main method for running this filter.
`void` | `setExpression(java.lang.String value)` Sets the expression used for filtering.
`void` | `setOptions(java.lang.String[] options)` Parses a given list of options.

Methods inherited from class weka.filters.SimpleBatchFilter
`batchFinished, input`

Methods inherited from class weka.filters.SimpleFilter
`debugTipText, getDebug, setDebug, setInputFormat`

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

### SubsetByExpression

    public SubsetByExpression()

Method Detail

### globalInfo

    public java.lang.String globalInfo()

  Returns a string describing this filter.

  Specified by:
    `globalInfo` in class `SimpleFilter`
  Returns:
    a description of the filter 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`
  Overrides:
    `listOptions` in class `SimpleFilter`
  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:

       -E <expr>
        The expression to use for filtering
        (default: true).

  Specified by:
    `setOptions` in interface `OptionHandler`
  Overrides:
    `setOptions` in class `SimpleFilter`
  Parameters:
    `options` - the list of options as an array of strings
  Throws:
    `java.lang.Exception` - if an option is not supported
  See Also:
    `SimpleFilter.reset()`

### getOptions

    public java.lang.String[] getOptions()

  Gets the current settings of the filter.

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

### 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`

### setExpression

    public void setExpression(java.lang.String value)

  Sets the expression used for filtering.

  Parameters:
    `value` - the expression

### getExpression

    public java.lang.String getExpression()

  Returns the expression used for filtering.

  Returns:
    the expression

### expressionTipText

    public java.lang.String expressionTipText()

  Returns the tip text for this property.

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

### 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[] args)

  Main method for running this filter.

  Parameters:
    `args` - arguments for the filter: use -h for help

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