Package weka.classifiers.evaluation

Class ConfusionMatrix

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable, RevisionHandler
    public class ConfusionMatrix
extends Matrix
    Cells of this matrix correspond to counts of the number (or weight) of predictions for each actual value / predicted value combination.
    Version:
    $Revision: 1.9 $
    Author:
    Len Trigg (len@reeltwo.com)
    See Also:
    Serialized Form

    • Constructor Detail

      • ConfusionMatrix

        public ConfusionMatrix​(java.lang.String[] classNames)
        Creates the confusion matrix with the given class names.
        Parameters:
        classNames - an array containing the names the classes.

    • Method Detail

      • makeWeighted

        public ConfusionMatrix makeWeighted​(CostMatrix costs)
                             throws java.lang.Exception
        Makes a copy of this ConfusionMatrix after applying the supplied CostMatrix to the cells. The resulting ConfusionMatrix can be used to get cost-weighted statistics.
        Parameters:
        costs - the CostMatrix.
        Returns:
        a ConfusionMatrix that has had costs applied.
        Throws:
        java.lang.Exception - if the CostMatrix is not of the same size as this ConfusionMatrix.

      • clone

        public java.lang.Object clone()
        Creates and returns a clone of this object.
        Overrides:
        clone in class Matrix
        Returns:
        a clone of this instance.

      • size

        public int size()
        Gets the number of classes.
        Returns:
        the number of classes

      • className

        public java.lang.String className​(int index)
        Gets the name of one of the classes.
        Parameters:
        index - the index of the class.
        Returns:
        the class name.

      • addPrediction

        public void addPrediction​(NominalPrediction pred)
                   throws java.lang.Exception
        Includes a prediction in the confusion matrix.
        Parameters:
        pred - the NominalPrediction to include
        Throws:
        java.lang.Exception - if no valid prediction was made (i.e. unclassified).

      • addPredictions

        public void addPredictions​(FastVector predictions)
                    throws java.lang.Exception
        Includes a whole bunch of predictions in the confusion matrix.
        Parameters:
        predictions - a FastVector containing the NominalPredictions to include
        Throws:
        java.lang.Exception - if no valid prediction was made (i.e. unclassified).

      • getTwoClassStats

        public TwoClassStats getTwoClassStats​(int classIndex)
        Gets the performance with respect to one of the classes as a TwoClassStats object.
        Parameters:
        classIndex - the index of the class of interest.
        Returns:
        the generated TwoClassStats object.

      • correct

        public double correct()
        Gets the number of correct classifications (that is, for which a correct prediction was made). (Actually the sum of the weights of these classifications)
        Returns:
        the number of correct classifications

      • incorrect

        public double incorrect()
        Gets the number of incorrect classifications (that is, for which an incorrect prediction was made). (Actually the sum of the weights of these classifications)
        Returns:
        the number of incorrect classifications

      • total

        public double total()
        Gets the number of predictions that were made (actually the sum of the weights of predictions where the class value was known).
        Returns:
        the number of predictions with known class

      • errorRate

        public double errorRate()
        Returns the estimated error rate.
        Returns:
        the estimated error rate (between 0 and 1).

      • toString

        public java.lang.String toString()
        Calls toString() with a default title.
        Overrides:
        toString in class Matrix
        Returns:
        the confusion matrix as a string

      • toString

        public java.lang.String toString​(java.lang.String title)
        Outputs the performance statistics as a classification confusion matrix. For each class value, shows the distribution of predicted class values.
        Parameters:
        title - the title for the confusion matrix
        Returns:
        the confusion matrix as a String