weka.filters
Class Filter

java.lang.Object
  weka.filters.Filter

All Implemented Interfaces:

Serializable, CapabilitiesHandler, RevisionHandler

Direct Known Subclasses:

AbstractTimeSeries, Add, AddCluster, AddExpression, AddID, AddNoise, AddUserFields, AddValues, AllFilter, AttributeSelection, ChangeDateFormat, ClassOrder, ClusterMembership, Copy, Discretize, FirstOrder, MakeIndicator, MergeManyValues, MergeTwoValues, NominalToBinary, NominalToBinary, NominalToString, NonSparseToSparse, NumericTransform, Obfuscate, PartitionMembership, PotentialClassIgnorer, PrincipalComponents, Randomize, RandomProjection, Remove, RemoveFolds, RemoveFrequentValues, RemoveMisclassified, RemovePercentage, RemoveRange, RemoveType, RemoveUseless, RemoveWithValues, Reorder, Resample, Resample, ReservoirSample, SimpleFilter, SparseToNonSparse, SpreadSubsample, StratifiedRemoveFolds, StringToNominal, StringToWordVector, SwapValues

public abstract class Filter
extends Object
implements Serializable, CapabilitiesHandler, RevisionHandler

An abstract class for instance filters: objects that take instances as input, carry out some transformation on the instance and then output the instance. The method implementations in this class assume that most of the work will be done in the methods overridden by subclasses.

A simple example of filter use. This example doesn't remove instances from the output queue until all instances have been input, so has higher memory consumption than an approach that uses output instances as they are made available:

  Filter filter = ..some type of filter..
  Instances instances = ..some instances..
  for (int i = 0; i < data.numInstances(); i++) {
    filter.input(data.instance(i));
  }
  filter.batchFinished();
  Instances newData = filter.outputFormat();
  Instance processed;
  while ((processed = filter.output()) != null) {
    newData.add(processed);
  }
  ..do something with newData..
 

Version:

$Revision: 8034 $

Author:

Len Trigg ([email protected])

See Also:

Serialized Form

Constructor Summary

Filter()

Method Summary

static void	batchFilterFile(Filter filter, String[] options) Method for testing filters ability to process multiple batches.
boolean	batchFinished() Signify that this batch of input to the filter is finished.
static void	filterFile(Filter filter, String[] options) Method for testing filters.
Capabilities	getCapabilities() Returns the Capabilities of this filter.
Capabilities	getCapabilities(Instances data) Returns the Capabilities of this filter, customized based on the data.
Instances	getOutputFormat() Gets the format of the output instances.
String	getRevision() Returns the revision string.
boolean	input(Instance instance) Input an instance for filtering.
boolean	isFirstBatchDone() Returns true if the first batch of instances got processed.
boolean	isNewBatch() Returns true if the a new batch was started, either a new instance of the filter was created or the batchFinished() method got called.
boolean	isOutputFormatDefined() Returns whether the output format is ready to be collected
static void	main(String[] args) Main method for testing this class.
static Filter[]	makeCopies(Filter model, int num) Creates a given number of deep copies of the given filter using serialization.
static Filter	makeCopy(Filter model) Creates a deep copy of the given filter using serialization.
boolean	mayRemoveInstanceAfterFirstBatchDone() Default implementation returns false.
int	numPendingOutput() Returns the number of instances pending output
Instance	output() Output an instance after filtering and remove from the output queue.
Instance	outputPeek() Output an instance after filtering but do not remove from the output queue.
static void	runFilter(Filter filter, String[] options) runs the filter instance with the given options.
boolean	setInputFormat(Instances instanceInfo) Sets the format of the input instances.
String	toString() Returns a description of the filter, by default only the classname.
static Instances	useFilter(Instances data, Filter filter) Filters an entire set of instances through a filter and returns the new set.
static String	wekaStaticWrapper(Sourcable filter, String className, Instances input, Instances output) generates source code from the filter

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Filter

public Filter()

Method Detail

isNewBatch

public boolean isNewBatch()

Returns true if the a new batch was started, either a new instance of the filter was created or the batchFinished() method got called.

Returns:

true if a new batch has been initiated

See Also:

m_NewBatch, batchFinished()

isFirstBatchDone

public boolean isFirstBatchDone()

Returns true if the first batch of instances got processed. Necessary for supervised filters, which "learn" from the first batch and then shouldn't get updated with subsequent calls of batchFinished().

Returns:

true if the first batch has been processed

See Also:

m_FirstBatchDone, batchFinished()

mayRemoveInstanceAfterFirstBatchDone

public boolean mayRemoveInstanceAfterFirstBatchDone()

Default implementation returns false. Some filters may not necessarily be able to produce an instance for output for every instance input after the first batch has been completed - such filters should override this method and return true.

Returns:

false by default

getCapabilities

public Capabilities getCapabilities()

Returns the Capabilities of this filter. Derived filters have to override this method to enable capabilities.

Specified by:

getCapabilities in interface CapabilitiesHandler

Returns:

the capabilities of this object

See Also:

Capabilities

getRevision

public String getRevision()

Returns the revision string.

Specified by:

getRevision in interface RevisionHandler

Returns:

the revision

getCapabilities

public Capabilities getCapabilities(Instances data)

Returns the Capabilities of this filter, customized based on the data. I.e., if removes all class capabilities, in case there's not class attribute present or removes the NO_CLASS capability, in case that there's a class present.

Parameters:

data - the data to use for customization

Returns:

the capabilities of this object, based on the data

See Also:

getCapabilities()

setInputFormat

public boolean setInputFormat(Instances instanceInfo)
                       throws Exception

Sets the format of the input instances. If the filter is able to determine the output format before seeing any input instances, it does so here. This default implementation clears the output format and output queue, and the new batch flag is set. Overriders should call super.setInputFormat(Instances)

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:

Exception - if the inputFormat can't be set successfully

getOutputFormat

public Instances getOutputFormat()

Gets the format of the output instances. This should only be called after input() or batchFinished() has returned true. The relation name of the output instances should be changed to reflect the action of the filter (eg: add the filter name and options).

Returns:

an Instances object containing the output instance structure only.

Throws:

NullPointerException - if no input structure has been defined (or the output format hasn't been determined yet)

input

public boolean input(Instance instance)
              throws Exception

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, in which case output instances should be collected after calling batchFinished(). If the input marks the start of a new batch, the output queue is cleared. This default implementation assumes all instance conversion will occur when batchFinished() is called.

Parameters:

instance - the input instance

Returns:

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

Throws:

NullPointerException - if the input format has not been defined.

Exception - if the input instance was not of the correct format or if there was a problem with the filtering.

batchFinished

public boolean batchFinished()
                      throws Exception

Signify 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. Any subsequent instances filtered should be filtered based on setting obtained from the first batch (unless the inputFormat has been re-assigned or new options have been set). This default implementation assumes all instance processing occurs during inputFormat() and input().

Returns:

true if there are instances pending output

Throws:

NullPointerException - if no input structure has been defined,

Exception - if there was a problem finishing the batch.

output

public Instance output()

Output an instance after filtering and remove from the output queue.

Returns:

the instance that has most recently been filtered (or null if the queue is empty).

Throws:

NullPointerException - if no output structure has been defined

outputPeek

public Instance outputPeek()

Output an instance after filtering but do not remove from the output queue.

Returns:

the instance that has most recently been filtered (or null if the queue is empty).

Throws:

NullPointerException - if no input structure has been defined

numPendingOutput

public int numPendingOutput()

Returns the number of instances pending output

Returns:

the number of instances pending output

Throws:

NullPointerException - if no input structure has been defined

isOutputFormatDefined

public boolean isOutputFormatDefined()

Returns whether the output format is ready to be collected

Returns:

true if the output format is set

makeCopy

public static Filter makeCopy(Filter model)
                       throws Exception

Creates a deep copy of the given filter using serialization.

Parameters:

model - the filter to copy

Returns:

a deep copy of the filter

Throws:

Exception - if an error occurs

makeCopies

public static Filter[] makeCopies(Filter model,
                                  int num)
                           throws Exception

Creates a given number of deep copies of the given filter using serialization.

Parameters:

model - the filter to copy

num - the number of filter copies to create.

Returns:

an array of filters.

Throws:

Exception - if an error occurs

useFilter

public static Instances useFilter(Instances data,
                                  Filter filter)
                           throws Exception

Filters an entire set of instances through a filter and returns the new set.

Parameters:

data - the data to be filtered

filter - the filter to be used

Returns:

the filtered set of data

Throws:

Exception - if the filter can't be used successfully

toString

public String toString()

Returns a description of the filter, by default only the classname.

Overrides:

toString in class Object

Returns:

a string describing the filter

wekaStaticWrapper

public static String wekaStaticWrapper(Sourcable filter,
                                       String className,
                                       Instances input,
                                       Instances output)
                                throws Exception

generates source code from the filter

Parameters:

filter - the filter to output as source

className - the name of the generated class

input - the input data the header is generated for

output - the output data the header is generated for

Returns:

the generated source code

Throws:

Exception - if source code cannot be generated

filterFile

public static void filterFile(Filter filter,
                              String[] options)
                       throws Exception

Method for testing filters.

Parameters:

filter - the filter to use

options - should contain the following arguments:
-i input_file
-o output_file
-c class_index
-z classname (for filters implementing weka.filters.Sourcable)
or -h for help on options

Throws:

Exception - if something goes wrong or the user requests help on command options

batchFilterFile

public static void batchFilterFile(Filter filter,
                                   String[] options)
                            throws Exception

Method for testing filters ability to process multiple batches.

Parameters:

filter - the filter to use

options - should contain the following arguments:
-i (first) input file
-o (first) output file
-r (second) input file
-s (second) output file
-c class_index
-z classname (for filters implementing weka.filters.Sourcable)
or -h for help on options

Throws:

Exception - if something goes wrong or the user requests help on command options

runFilter

public static void runFilter(Filter filter,
                             String[] options)

runs the filter instance with the given options.

Parameters:

filter - the filter to run

options - the commandline options

main

public static void main(String[] args)

Main method for testing this class.

Parameters:

args - should contain arguments to the filter: use -h for help