weka.attributeSelection

## Class PrincipalComponents

- java.lang.Object
- - weka.attributeSelection.ASEvaluation
  - - weka.attributeSelection.UnsupervisedAttributeEvaluator
    - - weka.attributeSelection.PrincipalComponents

- All Implemented Interfaces:
    java.io.Serializable, AttributeEvaluator, AttributeTransformer, CapabilitiesHandler, CapabilitiesIgnorer, OptionHandler, RevisionHandler

      public class PrincipalComponents
      extends UnsupervisedAttributeEvaluator
      implements AttributeTransformer, OptionHandler

  Performs a principal components analysis and transformation of the data. Use in conjunction with a Ranker search. Dimensionality reduction is accomplished by choosing enough eigenvectors to account for some percentage of the variance in the original data---default 0.95 (95%). Attribute noise can be filtered by transforming to the PC space, eliminating some of the worst eigenvectors, and then transforming back to the original space.

  Valid options are:

       -C
        Center (rather than standardize) the
        data and compute PCA using the covariance (rather
         than the correlation) matrix.

       -R
        Retain enough PC attributes to account
        for this proportion of variance in the original data.
        (default = 0.95)

       -O
        Transform through the PC space and
        back to the original space.

       -A
        Maximum number of attributes to include in
        transformed attribute names. (-1 = include all)

  Version:
    $Revision: 11518 $
  Author:
    Mark Hall (mhall@cs.waikato.ac.nz), Gabi Schmidberger (gabi@cs.waikato.ac.nz)
  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `PrincipalComponents()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `buildEvaluator(Instances data)` Initializes principal components and performs the analysis
    `java.lang.String` | `centerDataTipText()` Returns the tip text for this property
    `Instance` | `convertInstance(Instance instance)` Transform an instance in original (unormalized) format.
    `double` | `evaluateAttribute(int att)` Evaluates the merit of a transformed attribute.
    `Capabilities` | `getCapabilities()` Returns the capabilities of this evaluator.
    `boolean` | `getCenterData()` Get whether to center (rather than standardize) the data.
    `double[][]` | `getCorrelationMatrix()` Return the correlation/covariance matrix
    `double[]` | `getEigenValues()` Return the eigenvalues corresponding to the eigenvectors
    `Instances` | `getFilteredInputFormat()` Return the header of the training data after all filtering - i.e missing values and nominal to binary.
    `int` | `getMaximumAttributeNames()` Gets maximum number of attributes to include in transformed attribute names.
    `java.lang.String[]` | `getOptions()` Gets the current settings of PrincipalComponents
    `java.lang.String` | `getRevision()` Returns the revision string.
    `boolean` | `getTransformBackToOriginal()` Gets whether the data is to be transformed back to the original space.
    `double[][]` | `getUnsortedEigenVectors()` Return the unsorted eigenvectors
    `double` | `getVarianceCovered()` Gets the proportion of total variance to account for when retaining principal components
    `java.lang.String` | `globalInfo()` Returns a string describing this attribute transformer
    `java.util.Enumeration<Option>` | `listOptions()` Returns an enumeration describing the available options.
    `static void` | `main(java.lang.String[] argv)` Main method for testing this class
    `static java.lang.String` | `matrixToString(double[][] matrix)` Return a matrix as a String
    `java.lang.String` | `maximumAttributeNamesTipText()` Returns the tip text for this property
    `void` | `setCenterData(boolean center)` Set whether to center (rather than standardize) the data.
    `void` | `setMaximumAttributeNames(int m)` Sets maximum number of attributes to include in transformed attribute names.
    `void` | `setOptions(java.lang.String[] options)` Parses a given list of options.
    `void` | `setTransformBackToOriginal(boolean b)` Sets whether the data should be transformed back to the original space
    `void` | `setVarianceCovered(double vc)` Sets the amount of variance to account for when retaining principal components
    `java.lang.String` | `toString()` Returns a description of this attribute transformer
    `java.lang.String` | `transformBackToOriginalTipText()` Returns the tip text for this property
    `Instances` | `transformedData(Instances data)` Gets the transformed training data.
    `Instances` | `transformedHeader()` Returns just the header for the transformed data (ie.
    `java.lang.String` | `varianceCoveredTipText()` Returns the tip text for this property

    - ### Methods inherited from class weka.attributeSelection.ASEvaluation

      `clean, doNotCheckCapabilitiesTipText, forName, getDoNotCheckCapabilities, makeCopies, postProcess, runEvaluator, setDoNotCheckCapabilities`

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### PrincipalComponents

          public PrincipalComponents()

  - ### Method Detail

    - #### globalInfo

          public java.lang.String globalInfo()

      Returns a string describing this attribute transformer
      Returns:
        a description of the evaluator suitable for displaying in the explorer/experimenter gui

    - #### 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:

           -C
            Center (rather than standardize) the
            data and compute PCA using the covariance (rather
             than the correlation) matrix.

           -R
            Retain enough PC attributes to account
            for this proportion of variance in the original data.
            (default = 0.95)

           -O
            Transform through the PC space and
            back to the original space.

           -A
            Maximum number of attributes to include in
            transformed attribute names. (-1 = include all)

      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

    - #### centerDataTipText

          public java.lang.String centerDataTipText()

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

    - #### setCenterData

          public void setCenterData(boolean center)

      Set whether to center (rather than standardize) the data. If set to true then PCA is computed from the covariance rather than correlation matrix.
      Parameters:
        `center` - true if the data is to be centered rather than standardized

    - #### getCenterData

          public boolean getCenterData()

      Get whether to center (rather than standardize) the data. If true then PCA is computed from the covariance rather than correlation matrix.
      Returns:
        true if the data is to be centered rather than standardized.

    - #### varianceCoveredTipText

          public java.lang.String varianceCoveredTipText()

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

    - #### setVarianceCovered

          public void setVarianceCovered(double vc)

      Sets the amount of variance to account for when retaining principal components
      Parameters:
        `vc` - the proportion of total variance to account for

    - #### getVarianceCovered

          public double getVarianceCovered()

      Gets the proportion of total variance to account for when retaining principal components
      Returns:
        the proportion of variance to account for

    - #### maximumAttributeNamesTipText

          public java.lang.String maximumAttributeNamesTipText()

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

    - #### setMaximumAttributeNames

          public void setMaximumAttributeNames(int m)

      Sets maximum number of attributes to include in transformed attribute names.
      Parameters:
        `m` - the maximum number of attributes

    - #### getMaximumAttributeNames

          public int getMaximumAttributeNames()

      Gets maximum number of attributes to include in transformed attribute names.
      Returns:
        the maximum number of attributes

    - #### transformBackToOriginalTipText

          public java.lang.String transformBackToOriginalTipText()

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

    - #### setTransformBackToOriginal

          public void setTransformBackToOriginal(boolean b)

      Sets whether the data should be transformed back to the original space
      Parameters:
        `b` - true if the data should be transformed back to the original space

    - #### getTransformBackToOriginal

          public boolean getTransformBackToOriginal()

      Gets whether the data is to be transformed back to the original space.
      Returns:
        true if the data is to be transformed back to the original space

    - #### getOptions

          public java.lang.String[] getOptions()

      Gets the current settings of PrincipalComponents
      Specified by:
        `getOptions` in interface `OptionHandler`
      Returns:
        an array of strings suitable for passing to setOptions()

    - #### getCapabilities

          public Capabilities getCapabilities()

      Returns the capabilities of this evaluator.
      Specified by:
        `getCapabilities` in interface `CapabilitiesHandler`
      Overrides:
        `getCapabilities` in class `ASEvaluation`
      Returns:
        the capabilities of this evaluator
      See Also:
        `Capabilities`

    - #### buildEvaluator

          public void buildEvaluator(Instances data)
                              throws java.lang.Exception

      Initializes principal components and performs the analysis
      Specified by:
        `buildEvaluator` in class `ASEvaluation`
      Parameters:
        `data` - the instances to analyse/transform
      Throws:
        `java.lang.Exception` - if analysis fails

    - #### transformedHeader

          public Instances transformedHeader()
                                      throws java.lang.Exception

      Returns just the header for the transformed data (ie. an empty set of instances. This is so that AttributeSelection can determine the structure of the transformed data without actually having to get all the transformed data through transformedData().
      Specified by:
        `transformedHeader` in interface `AttributeTransformer`
      Returns:
        the header of the transformed data.
      Throws:
        `java.lang.Exception` - if the header of the transformed data can't be determined.

    - #### getFilteredInputFormat

          public Instances getFilteredInputFormat()

      Return the header of the training data after all filtering - i.e missing values and nominal to binary.
      Returns:
        the header of the training data after all filtering.

    - #### getCorrelationMatrix

          public double[][] getCorrelationMatrix()

      Return the correlation/covariance matrix
      Returns:
        the correlation or covariance matrix

    - #### getUnsortedEigenVectors

          public double[][] getUnsortedEigenVectors()

      Return the unsorted eigenvectors
      Returns:
        the unsorted eigenvectors

    - #### getEigenValues

          public double[] getEigenValues()

      Return the eigenvalues corresponding to the eigenvectors
      Returns:
        the eigenvalues

    - #### transformedData

          public Instances transformedData(Instances data)
                                    throws java.lang.Exception

      Gets the transformed training data.
      Specified by:
        `transformedData` in interface `AttributeTransformer`
      Returns:
        the transformed training data
      Throws:
        `java.lang.Exception` - if transformed data can't be returned

    - #### evaluateAttribute

          public double evaluateAttribute(int att)
                                   throws java.lang.Exception

      Evaluates the merit of a transformed attribute. This is defined to be 1 minus the cumulative variance explained. Merit can't be meaningfully evaluated if the data is to be transformed back to the original space.
      Specified by:
        `evaluateAttribute` in interface `AttributeEvaluator`
      Parameters:
        `att` - the attribute to be evaluated
      Returns:
        the merit of a transformed attribute
      Throws:
        `java.lang.Exception` - if attribute can't be evaluated

    - #### toString

          public java.lang.String toString()

      Returns a description of this attribute transformer
      Overrides:
        `toString` in class `java.lang.Object`
      Returns:
        a String describing this attribute transformer

    - #### matrixToString

          public static java.lang.String matrixToString(double[][] matrix)

      Return a matrix as a String
      Parameters:
        `matrix` - that is decribed as a string
      Returns:
        a String describing a matrix

    - #### convertInstance

          public Instance convertInstance(Instance instance)
                                   throws java.lang.Exception

      Transform an instance in original (unormalized) format. Convert back to the original space if requested.
      Specified by:
        `convertInstance` in interface `AttributeTransformer`
      Parameters:
        `instance` - an instance in the original (unormalized) format
      Returns:
        a transformed instance
      Throws:
        `java.lang.Exception` - if instance cant be transformed

    - #### getRevision

          public java.lang.String getRevision()

      Returns the revision string.
      Specified by:
        `getRevision` in interface `RevisionHandler`
      Overrides:
        `getRevision` in class `ASEvaluation`
      Returns:
        the revision

    - #### main

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

      Main method for testing this class
      Parameters:
        `argv` - should contain the command line arguments to the evaluator/transformer (see AttributeSelection)