weka.filters
Class SimpleBatchFilter

java.lang.Object
  weka.filters.Filter
      weka.filters.SimpleFilter
          weka.filters.SimpleBatchFilter

All Implemented Interfaces:

Serializable, CapabilitiesHandler, OptionHandler, RevisionHandler

Direct Known Subclasses:

AddClassification, InterquartileRange, KernelFilter, NumericToNominal, PartitionedMultiFilter, SubsetByExpression

public abstract class SimpleBatchFilter
extends SimpleFilter

This filter is a superclass for simple batch filters.

General notes:

• After adding instances to the filter via input(Instance) one always has to call batchFinished() to make them available via output().
• After the first call of batchFinished() the field m_FirstBatchDone is set to true.

Example:
The following code snippet uses the filter SomeFilter on a dataset that is loaded from filename.

 import weka.core.*;
 import weka.filters.*;
 import java.io.*;
 ...
 SomeFilter filter = new SomeFilter();
 // set necessary options for the filter
 Instances data = new Instances(
                    new BufferedReader(
                      new FileReader(filename)));
 Instances filteredData = Filter.useFilter(data, filter);
 

Implementation:
Only the following abstract methods need to be implemented:

• globalInfo()
• determineOutputFormat(Instances)
• process(Instances)

And the getCapabilities() method must return what kind of attributes and classes the filter can handle.

If more options are necessary, then the following methods need to be overriden:

• listOptions()
• setOptions(String[])
• getOptions()

To make the filter available from commandline one must add the following main method for correct execution (<Filtername> must be replaced with the actual filter classname):

  public static void main(String[] args) {
    runFilter(new <Filtername>(), args);
  }
 

Example implementation:

 import weka.core.*;
 import weka.core.Capabilities.*;
 import weka.filters.*;

 public class SimpleBatch
   extends SimpleBatchFilter {
   
   public String globalInfo() {
     return "A simple batch filter that adds an additional attribute 'bla' at the end containing the index of the processed instance.";
   }
     
   public Capabilities getCapabilities() {
     Capabilities result = super.getCapabilities();
     result.enableAllAttributes();
     result.enableAllClasses();
     result.enable(Capability.NO_CLASS);  // filter doesn't need class to be set
     return result;
   }
 
   protected Instances determineOutputFormat(Instances inputFormat) {
     Instances result = new Instances(inputFormat, 0);
     result.insertAttributeAt(new Attribute("bla"), result.numAttributes());
     return result;
   }
 
   protected Instances process(Instances inst) {
     Instances result = new Instances(determineOutputFormat(inst), 0);
     for (int i = 0; i < inst.numInstances(); i++) {
       double[] values = new double[result.numAttributes()];
       for (int n = 0; n < inst.numAttributes(); n++)
         values[n] = inst.instance(i).value(n);
       values[values.length - 1] = i;
       result.add(new Instance(1, values));
     }
     return result;
   }
 
   public static void main(String[] args) {
     runFilter(new SimpleBatch(), args);
   }
 }
 

Options:
Valid filter-specific options are:

-D
Turns on output of debugging information.

Version:

$Revision: 8954 $

Author:

FracPete (fracpete at waikato dot ac dot nz)

See Also:

SimpleStreamFilter, input(Instance), batchFinished(), Filter.m_FirstBatchDone, Serialized Form

Constructor Summary

SimpleBatchFilter()

Method Summary

boolean	batchFinished() Signify that this batch of input to the filter is finished.
boolean	input(Instance instance) Input an instance for filtering.

Methods inherited from class weka.filters.SimpleFilter

debugTipText, getDebug, getOptions, globalInfo, listOptions, setDebug, setInputFormat, setOptions

Methods inherited from class weka.filters.Filter

batchFilterFile, filterFile, getCapabilities, getCapabilities, getOutputFormat, getRevision, isFirstBatchDone, isNewBatch, isOutputFormatDefined, main, makeCopies, makeCopy, mayRemoveInstanceAfterFirstBatchDone, numPendingOutput, output, outputPeek, runFilter, toString, useFilter, wekaStaticWrapper

Methods inherited from class java.lang.Object

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

Constructor Detail

SimpleBatchFilter

public SimpleBatchFilter()

Method Detail

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 Filter

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:

batchFinished()

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 setInputFormat has been re-assigned or new options have been set). Sets m_FirstBatchDone and m_NewBatch to true.

Overrides:

batchFinished in class Filter

Returns:

true if there are instances pending output

Throws:

IllegalStateException - if no input format has been set.

Exception - if something goes wrong

See Also:

Filter.m_NewBatch, Filter.m_FirstBatchDone