weka.filters

## Class Filter

- java.lang.Object
- - weka.filters.Filter

- All Implemented Interfaces:
    java.io.Serializable, CapabilitiesHandler, CapabilitiesIgnorer, OptionHandler, 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, RenameNominalValues, Reorder, Resample, Resample, ReservoirSample, SimpleFilter, SparseToNonSparse, SpreadSubsample, StratifiedRemoveFolds, StringToNominal, StringToWordVector, SwapValues

      public abstract class Filter
      extends java.lang.Object
      implements java.io.Serializable, CapabilitiesHandler, RevisionHandler, OptionHandler, CapabilitiesIgnorer

  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: 11352 $
  Author:
    Len Trigg (trigg@cs.waikato.ac.nz)
  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `Filter()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static void` | `batchFilterFile(Filter filter, java.lang.String[] options)` Method for testing filters ability to process multiple batches.
    `boolean` | `batchFinished()` Signify that this batch of input to the filter is finished.
    `java.lang.String` | `debugTipText()` Returns the tip text for this property
    `java.lang.String` | `doNotCheckCapabilitiesTipText()` Returns the tip text for this property
    `static void` | `filterFile(Filter filter, java.lang.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.
    `boolean` | `getDebug()` Get whether debugging is turned on.
    `boolean` | `getDoNotCheckCapabilities()` Get whether capabilities checking is turned off.
    `java.lang.String[]` | `getOptions()` Gets the current settings of the filter.
    `Instances` | `getOutputFormat()` Gets the format of the output instances.
    `java.lang.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
    `java.util.Enumeration<Option>` | `listOptions()` Returns an enumeration describing the available options.
    `static void` | `main(java.lang.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, java.lang.String[] options)` runs the filter instance with the given options.
    `void` | `setDebug(boolean debug)` Set debugging mode.
    `void` | `setDoNotCheckCapabilities(boolean doNotCheckCapabilities)` Set whether not to check capabilities.
    `boolean` | `setInputFormat(Instances instanceInfo)` Sets the format of the input instances.
    `void` | `setOptions(java.lang.String[] options)` Parses a given list of options.
    `java.lang.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 java.lang.String` | `wekaStaticWrapper(Sourcable filter, java.lang.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 java.lang.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 java.lang.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:
        `java.lang.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:
        `java.lang.NullPointerException` - if no input structure has been defined (or the output format hasn't been determined yet)

    - #### input

          public boolean input(Instance instance)
                        throws java.lang.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:
        `java.lang.NullPointerException` - if the input format has not been defined.
        `java.lang.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 java.lang.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:
        `java.lang.NullPointerException` - if no input structure has been defined,
        `java.lang.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:
        `java.lang.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:
        `java.lang.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:
        `java.lang.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 java.lang.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:
        `java.lang.Exception` - if an error occurs

    - #### makeCopies

          public static Filter[] makeCopies(Filter model,
                            int num)
                                     throws java.lang.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:
        `java.lang.Exception` - if an error occurs

    - #### useFilter

          public static Instances useFilter(Instances data,
                            Filter filter)
                                     throws java.lang.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:
        `java.lang.Exception` - if the filter can't be used successfully

    - #### toString

          public java.lang.String toString()

      Returns a description of the filter, by default only the classname.
      Overrides:
        `toString` in class `java.lang.Object`
      Returns:
        a string describing the filter

    - #### wekaStaticWrapper

          public static java.lang.String wekaStaticWrapper(Sourcable filter,
                                           java.lang.String className,
                                           Instances input,
                                           Instances output)
                                                    throws java.lang.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:
        `java.lang.Exception` - if source code cannot be generated

    - #### filterFile

          public static void filterFile(Filter filter,
                        java.lang.String[] options)
                                 throws java.lang.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)
        -decimal num (the number of decimal places to use in the output; default = 6)
        or -h for help on options
      Throws:
        `java.lang.Exception` - if something goes wrong or the user requests help on command options

    - #### batchFilterFile

          public static void batchFilterFile(Filter filter,
                             java.lang.String[] options)
                                      throws java.lang.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)
        -decimal num (the number of decimal places to use in the output; default = 6)
        or -h for help on options
      Throws:
        `java.lang.Exception` - if something goes wrong or the user requests help on command options

    - #### runFilter

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

      runs the filter instance with the given options.
      Parameters:
        `filter` - the filter to run
        `options` - the commandline options

    - #### listOptions

          public java.util.Enumeration<Option> 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 a given list of options. Valid options are:

      -D
      If set, filter is run in debug mode and may output additional info to the console.

      -do-not-check-capabilities
      If set, filter capabilities are not checked before filter is built (use with caution).

      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

    - #### setDebug

          public void setDebug(boolean debug)

      Set debugging mode.
      Parameters:
        `debug` - true if debug output should be printed

    - #### getDebug

          public boolean getDebug()

      Get whether debugging is turned on.
      Returns:
        true if debugging output is on

    - #### debugTipText

          public java.lang.String debugTipText()

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

    - #### setDoNotCheckCapabilities

          public void setDoNotCheckCapabilities(boolean doNotCheckCapabilities)

      Set whether not to check capabilities.
      Specified by:
        `setDoNotCheckCapabilities` in interface `CapabilitiesIgnorer`
      Parameters:
        `doNotCheckCapabilities` - true if capabilities are not to be checked.

    - #### getDoNotCheckCapabilities

          public boolean getDoNotCheckCapabilities()

      Get whether capabilities checking is turned off.
      Specified by:
        `getDoNotCheckCapabilities` in interface `CapabilitiesIgnorer`
      Returns:
        true if capabilities checking is turned off.

    - #### doNotCheckCapabilitiesTipText

          public java.lang.String doNotCheckCapabilitiesTipText()

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

    - #### main

          public static void main(java.lang.String[] args)

      Main method for testing this class.
      Parameters:
        `args` - should contain arguments to the filter: use -h for help