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## weka.classifiers.meta
Class MultiClassClassifier

    java.lang.Object
      weka.classifiers.Classifier
          weka.classifiers.SingleClassifierEnhancer
              weka.classifiers.RandomizableSingleClassifierEnhancer
                  weka.classifiers.meta.MultiClassClassifier

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

    public class MultiClassClassifier

extends RandomizableSingleClassifierEnhancer
implements OptionHandler

A metaclassifier for handling multi-class datasets with 2-class classifiers. This classifier is also capable of applying error correcting output codes for increased accuracy.

Valid options are:

     -M <num>
      Sets the method to use. Valid values are 0 (1-against-all),
      1 (random codes), 2 (exhaustive code), and 3 (1-against-1). (default 0)

     -R <num>
      Sets the multiplier when using random codes. (default 2.0)

     -P
      Use pairwise coupling (only has an effect for 1-against1)

     -S <num>
      Random number seed.
      (default 1)

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

     -W
      Full name of base classifier.
      (default: weka.classifiers.functions.Logistic)

     Options specific to classifier weka.classifiers.functions.Logistic:

     -D
      Turn on debugging output.

     -R <ridge>
      Set the ridge in the log-likelihood.

     -M <number>
      Set the maximum number of iterations (default -1, until convergence).

Version:
  $Revision: 1.48 $
Author:
  Eibe Frank (eibe@cs.waikato.ac.nz), Len Trigg (len@reeltwo.com), Richard Kirkby (rkirkby@cs.waikato.ac.nz)
See Also:
  Serialized Form

Field Summary
`static int` | `METHOD_1_AGAINST_1` 1-against-1
`static int` | `METHOD_1_AGAINST_ALL` 1-against-all
`static int` | `METHOD_ERROR_EXHAUSTIVE` exhaustive correction code
`static int` | `METHOD_ERROR_RANDOM` random correction code
`static Tag[]` | `TAGS_METHOD` The error correction modes

Constructor Summary
`MultiClassClassifier()` Constructor.

Method Summary
`void` | `buildClassifier(Instances insts)` Builds the classifiers.
`double[]` | `distributionForInstance(Instance inst)` Returns the distribution for an instance.
`Capabilities` | `getCapabilities()` Returns default capabilities of the classifier.
`SelectedTag` | `getMethod()` Gets the method used.
`java.lang.String[]` | `getOptions()` Gets the current settings of the Classifier.
`double` | `getRandomWidthFactor()` Gets the multiplier when generating random codes.
`java.lang.String` | `getRevision()` Returns the revision string.
`boolean` | `getUsePairwiseCoupling()` Gets whether to use pairwise coupling with 1-vs-1 classification to improve probability estimates.
`java.lang.String` | `globalInfo()`
`double[]` | `individualPredictions(Instance inst)` Returns the individual predictions of the base classifiers for an instance.
`java.util.Enumeration` | `listOptions()` Returns an enumeration describing the available options
`static void` | `main(java.lang.String[] argv)` Main method for testing this class.
`java.lang.String` | `methodTipText()`
`static double[]` | `pairwiseCoupling(double[][] n, double[][] r)` Implements pairwise coupling.
`java.lang.String` | `randomWidthFactorTipText()`
`void` | `setMethod(SelectedTag newMethod)` Sets the method used.
`void` | `setOptions(java.lang.String[] options)` Parses a given list of options.
`void` | `setRandomWidthFactor(double newRandomWidthFactor)` Sets the multiplier when generating random codes.
`void` | `setUsePairwiseCoupling(boolean p)` Set whether to use pairwise coupling with 1-vs-1 classification to improve probability estimates.
`java.lang.String` | `toString()` Prints the classifiers.
`java.lang.String` | `usePairwiseCouplingTipText()`

Methods inherited from class weka.classifiers.RandomizableSingleClassifierEnhancer
`getSeed, seedTipText, setSeed`

Methods inherited from class weka.classifiers.SingleClassifierEnhancer
`classifierTipText, getClassifier, setClassifier`

Methods inherited from class weka.classifiers.Classifier
`classifyInstance, debugTipText, forName, getDebug, makeCopies, makeCopy, setDebug`

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

### METHOD_1_AGAINST_ALL

    public static final int METHOD_1_AGAINST_ALL

  1-against-all

  See Also:
    Constant Field Values

### METHOD_ERROR_RANDOM

    public static final int METHOD_ERROR_RANDOM

  random correction code

  See Also:
    Constant Field Values

### METHOD_ERROR_EXHAUSTIVE

    public static final int METHOD_ERROR_EXHAUSTIVE

  exhaustive correction code

  See Also:
    Constant Field Values

### METHOD_1_AGAINST_1

    public static final int METHOD_1_AGAINST_1

  1-against-1

  See Also:
    Constant Field Values

### TAGS_METHOD

    public static final Tag[] TAGS_METHOD

  The error correction modes

Constructor Detail

### MultiClassClassifier

    public MultiClassClassifier()

  Constructor.

Method Detail

### getCapabilities

    public Capabilities getCapabilities()

  Returns default capabilities of the classifier.

  Specified by:
    `getCapabilities` in interface `CapabilitiesHandler`
  Overrides:
    `getCapabilities` in class `SingleClassifierEnhancer`
  Returns:
    the capabilities of this classifier
  See Also:
    `Capabilities`

### buildClassifier

    public void buildClassifier(Instances insts)
                         throws java.lang.Exception

  Builds the classifiers.

  Specified by:
    `buildClassifier` in class `Classifier`
  Parameters:
    `insts` - the training data.
  Throws:
    `java.lang.Exception` - if a classifier can't be built

### individualPredictions

    public double[] individualPredictions(Instance inst)
                                   throws java.lang.Exception

  Returns the individual predictions of the base classifiers for an instance. Used by StackedMultiClassClassifier. Returns the probability for the second "class" predicted by each base classifier.

  Parameters:
    `inst` - the instance to get the prediction for
  Returns:
    the individual predictions
  Throws:
    `java.lang.Exception` - if the predictions can't be computed successfully

### distributionForInstance

    public double[] distributionForInstance(Instance inst)
                                     throws java.lang.Exception

  Returns the distribution for an instance.

  Overrides:
    `distributionForInstance` in class `Classifier`
  Parameters:
    `inst` - the instance to get the distribution for
  Returns:
    the distribution
  Throws:
    `java.lang.Exception` - if the distribution can't be computed successfully

### toString

    public java.lang.String toString()

  Prints the classifiers.

  Overrides:
    `toString` in class `java.lang.Object`
  Returns:
    a string representation of the classifier

### listOptions

    public java.util.Enumeration listOptions()

  Returns an enumeration describing the available options

  Specified by:
    `listOptions` in interface `OptionHandler`
  Overrides:
    `listOptions` in class `RandomizableSingleClassifierEnhancer`
  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:

       -M <num>
        Sets the method to use. Valid values are 0 (1-against-all),
        1 (random codes), 2 (exhaustive code), and 3 (1-against-1). (default 0)

       -R <num>
        Sets the multiplier when using random codes. (default 2.0)

       -P
        Use pairwise coupling (only has an effect for 1-against1)

       -S <num>
        Random number seed.
        (default 1)

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

       -W
        Full name of base classifier.
        (default: weka.classifiers.functions.Logistic)

       Options specific to classifier weka.classifiers.functions.Logistic:

       -D
        Turn on debugging output.

       -R <ridge>
        Set the ridge in the log-likelihood.

       -M <number>
        Set the maximum number of iterations (default -1, until convergence).

  Specified by:
    `setOptions` in interface `OptionHandler`
  Overrides:
    `setOptions` in class `RandomizableSingleClassifierEnhancer`
  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 Classifier.

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

### globalInfo

    public java.lang.String globalInfo()

  Returns:
    a description of the classifier suitable for displaying in the explorer/experimenter gui

### randomWidthFactorTipText

    public java.lang.String randomWidthFactorTipText()

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

### getRandomWidthFactor

    public double getRandomWidthFactor()

  Gets the multiplier when generating random codes. Will generate numClasses * m_RandomWidthFactor codes.

  Returns:
    the width multiplier

### setRandomWidthFactor

    public void setRandomWidthFactor(double newRandomWidthFactor)

  Sets the multiplier when generating random codes. Will generate numClasses * m_RandomWidthFactor codes.

  Parameters:
    `newRandomWidthFactor` - the new width multiplier

### methodTipText

    public java.lang.String methodTipText()

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

### getMethod

    public SelectedTag getMethod()

  Gets the method used. Will be one of METHOD_1_AGAINST_ALL, METHOD_ERROR_RANDOM, METHOD_ERROR_EXHAUSTIVE, or METHOD_1_AGAINST_1.

  Returns:
    the current method.

### setMethod

    public void setMethod(SelectedTag newMethod)

  Sets the method used. Will be one of METHOD_1_AGAINST_ALL, METHOD_ERROR_RANDOM, METHOD_ERROR_EXHAUSTIVE, or METHOD_1_AGAINST_1.

  Parameters:
    `newMethod` - the new method.

### setUsePairwiseCoupling

    public void setUsePairwiseCoupling(boolean p)

  Set whether to use pairwise coupling with 1-vs-1 classification to improve probability estimates.

  Parameters:
    `p` - true if pairwise coupling is to be used

### getUsePairwiseCoupling

    public boolean getUsePairwiseCoupling()

  Gets whether to use pairwise coupling with 1-vs-1 classification to improve probability estimates.

  Returns:
    true if pairwise coupling is to be used

### usePairwiseCouplingTipText

    public java.lang.String usePairwiseCouplingTipText()

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

### pairwiseCoupling

    public static double[] pairwiseCoupling(double[][] n,
                                            double[][] r)

  Implements pairwise coupling.

  Parameters:
    `n` - the sum of weights used to train each model
    `r` - the probability estimate from each model
  Returns:
    the coupled estimates

### getRevision

    public java.lang.String getRevision()

  Returns the revision string.

  Specified by:
    `getRevision` in interface `RevisionHandler`
  Overrides:
    `getRevision` in class `Classifier`
  Returns:
    the revision

### main

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

  Main method for testing this class.

  Parameters:
    `argv` - the options

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