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:

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).
 

 -F
  Apply the filter to instances that arrive after the first
  (training) batch. The default is to not apply the filter (i.e.
  always return the instance)
 

Version:

$Revision: 10215 $

Author:

fracpete (fracpete at waikato dot ac dot nz)

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
SubsetByExpression()

Method Summary

Methods

Modifier and Type	Method and Description
String	expressionTipText() Returns the tip text for this property.
String	filterAfterFirstBatchTipText() Returns the tip text for this property.
Capabilities	getCapabilities() Returns the Capabilities of this filter.
String	getExpression() Returns the expression used for filtering.
boolean	getFilterAfterFirstBatch() Get whether to apply the filter to instances that arrive once the first (training) batch has been seen.
String[]	getOptions() Gets the current settings of the filter.
String	getRevision() Returns the revision string.
String	globalInfo() Returns a string describing this filter.
boolean	input(Instance instance) Input an instance for filtering.
Enumeration<Option>	listOptions() Returns an enumeration describing the available options.
static void	main(String[] args) Main method for running this filter.
boolean	mayRemoveInstanceAfterFirstBatchDone() SubsetByExpression may return false from input() (thus not making an instance available immediately) even after the first batch has been completed if the user has opted to apply the filter to instances after the first batch (rather than just passing them through).
void	setExpression(String value) Sets the expression used for filtering.
void	setFilterAfterFirstBatch(boolean b) Set whether to apply the filter to instances that arrive once the first (training) batch has been seen.
void	setOptions(String[] options) Parses a given list of options.

Methods inherited from class weka.filters.SimpleBatchFilter

allowAccessToFullInputFormat, batchFinished

Methods inherited from class weka.filters.SimpleFilter

debugTipText, doNotCheckCapabilitiesTipText, getDebug, getDoNotCheckCapabilities, setDebug, setDoNotCheckCapabilities, setInputFormat

Methods inherited from class weka.filters.Filter

batchFilterFile, filterFile, getCapabilities, getOutputFormat, isFirstBatchDone, isNewBatch, isOutputFormatDefined, makeCopies, makeCopy, numPendingOutput, output, outputPeek, runFilter, 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 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

mayRemoveInstanceAfterFirstBatchDone

public boolean mayRemoveInstanceAfterFirstBatchDone()

SubsetByExpression may return false from input() (thus not making an instance available immediately) even after the first batch has been completed if the user has opted to apply the filter to instances after the first batch (rather than just passing them through).

Overrides:

mayRemoveInstanceAfterFirstBatchDone in class Filter

Returns:

true this filter may remove (consume) input instances after the first batch has been completed.

input

public boolean input(Instance instance)
              throws Exception

Input an instance for filtering. Filter requires all training instances be read before producing output (calling the method batchFinished() makes the data available). If this instance is part of a new batch, m_NewBatch is set to false.

Overrides:

input in class SimpleBatchFilter

Parameters:

instance - the input instance

Returns:

true if the filtered instance may now be collected with output().

Throws:

IllegalStateException - if no input structure has been defined

Exception - if something goes wrong

See Also:

SimpleBatchFilter.batchFinished()

listOptions

public Enumeration<Option> 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(String[] options)
                throws Exception

Parses a given list of options.

Valid options are:

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

 -F
  Apply the filter to instances that arrive after the first
  (training) batch. The default is to not apply the filter (i.e.
  always return the instance)
 

Specified by:

setOptions in interface OptionHandler

Overrides:

setOptions in class SimpleFilter

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 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 SimpleFilter

Returns:

the capabilities of this object

See Also:

Capabilities

setExpression

public void setExpression(String value)

Sets the expression used for filtering.

Parameters:

value - the expression

getExpression

public String getExpression()

Returns the expression used for filtering.

Returns:

the expression

expressionTipText

public String expressionTipText()

Returns the tip text for this property.

Returns:

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

setFilterAfterFirstBatch

public void setFilterAfterFirstBatch(boolean b)

Set whether to apply the filter to instances that arrive once the first (training) batch has been seen. The default is to not apply the filter and just return each instance input. This is so that, when used in the FilteredClassifier, a test instance does not get "consumed" by the filter and a prediction is always generated.

Parameters:

b - true if the filter should be applied to instances that arrive after the first (training) batch has been processed.

getFilterAfterFirstBatch

public boolean getFilterAfterFirstBatch()

Get whether to apply the filter to instances that arrive once the first (training) batch has been seen. The default is to not apply the filter and just return each instance input. This is so that, when used in the FilteredClassifier, a test instance does not get "consumed" by the filter and a prediction is always generated.

Returns:

true if the filter should be applied to instances that arrive after the first (training) batch has been processed.

filterAfterFirstBatchTipText

public String filterAfterFirstBatchTipText()

Returns the tip text for this property.

Returns:

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

getRevision

public 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(String[] args)

Main method for running this filter.

Parameters:

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