samoa-api/src/main/java/org/apache/samoa/evaluation/WindowClassificationPerformanceEvaluator.java

package org.apache.samoa.evaluation;

import java.util.List;

import org.apache.samoa.instances.Attribute;

/*
 * #%L
 * SAMOA
 * %%
 * Copyright (C) 2014 - 2015 Apache Software Foundation
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */

import org.apache.samoa.instances.Instance;
import org.apache.samoa.instances.Utils;
import org.apache.samoa.moa.AbstractMOAObject;
import org.apache.samoa.moa.core.Measurement;
import org.apache.samoa.moa.core.Vote;

import com.github.javacliparser.IntOption;

/**
 * Classification evaluator that updates evaluation results using a sliding window.
 * 
 * @author Albert Bifet (abifet at cs dot waikato dot ac dot nz)
 * @version $Revision: 7 $
 */
public class WindowClassificationPerformanceEvaluator extends AbstractMOAObject implements
    ClassificationPerformanceEvaluator {

  private static final long serialVersionUID = 1L;

  public IntOption widthOption = new IntOption("width",
      'w', "Size of Window", 1000);

  protected double TotalweightObserved = 0;

  protected Estimator weightObserved;

  protected Estimator weightCorrect;

  protected Estimator weightCorrectNoChangeClassifier;

  protected double lastSeenClass;

  protected Estimator[] columnKappa;

  protected Estimator[] rowKappa;

  protected Estimator[] classAccuracy;

  protected int numClasses;

  private String instanceIdentifier;
  private Instance lastSeenInstance;
  protected double[] classVotes;

  public class Estimator {

    protected double[] window;

    protected int posWindow;

    protected int lenWindow;

    protected int SizeWindow;

    protected double sum;

    public Estimator(int sizeWindow) {
      window = new double[sizeWindow];
      SizeWindow = sizeWindow;
      posWindow = 0;
      lenWindow = 0;
    }

    public void add(double value) {
      sum -= window[posWindow];
      sum += value;
      window[posWindow] = value;
      posWindow++;
      if (posWindow == SizeWindow) {
        posWindow = 0;
      }
      if (lenWindow < SizeWindow) {
        lenWindow++;
      }
    }

    public double total() {
      return sum;
    }

    public double length() {
      return lenWindow;
    }

  }

  /*
   * public void setWindowWidth(int w) { this.width = w; reset(); }
   */
  @Override
  public void reset() {
    reset(this.numClasses);
  }

  public void reset(int numClasses) {
    this.numClasses = numClasses;
    this.rowKappa = new Estimator[numClasses];
    this.columnKappa = new Estimator[numClasses];
    this.classAccuracy = new Estimator[numClasses];
    for (int i = 0; i < this.numClasses; i++) {
      this.rowKappa[i] = new Estimator(this.widthOption.getValue());
      this.columnKappa[i] = new Estimator(this.widthOption.getValue());
      this.classAccuracy[i] = new Estimator(this.widthOption.getValue());
    }
    this.weightCorrect = new Estimator(this.widthOption.getValue());
    this.weightCorrectNoChangeClassifier = new Estimator(this.widthOption.getValue());
    this.weightObserved = new Estimator(this.widthOption.getValue());
    this.TotalweightObserved = 0;
    this.lastSeenClass = 0;
  }

  @Override
  public void addResult(Instance inst, double[] classVotes, String instanceIndex) {
    double weight = inst.weight();
    int trueClass = (int) inst.classValue();
    if (weight > 0.0) {
      if (TotalweightObserved == 0) {
        reset(inst.numClasses());
      }
      this.TotalweightObserved += weight;
      this.weightObserved.add(weight);
      int predictedClass = Utils.maxIndex(classVotes);
      if (predictedClass == trueClass) {
        this.weightCorrect.add(weight);
      } else {
        this.weightCorrect.add(0);
      }
      // Add Kappa statistic information
      for (int i = 0; i < this.numClasses; i++) {
        this.rowKappa[i].add(i == predictedClass ? weight : 0);
        this.columnKappa[i].add(i == trueClass ? weight : 0);
      }
      if (this.lastSeenClass == trueClass) {
        this.weightCorrectNoChangeClassifier.add(weight);
      } else {
        this.weightCorrectNoChangeClassifier.add(0);
      }
      this.classAccuracy[trueClass].add(predictedClass == trueClass ? weight : 0.0);
      this.lastSeenClass = trueClass;
    }
  }

  @Override
  public Measurement[] getPerformanceMeasurements() {
    return new Measurement[] {
        new Measurement("classified instances",
            this.TotalweightObserved),
        new Measurement("classifications correct (percent)",
            getFractionCorrectlyClassified() * 100.0),
        new Measurement("Kappa Statistic (percent)",
            getKappaStatistic() * 100.0),
        new Measurement("Kappa Temporal Statistic (percent)",
            getKappaTemporalStatistic() * 100.0)
    };

  }

  /**
   * This method is used to retrieve predictions and votes (for classification only)
   * 
   * @return String This returns an array of predictions and votes objects.
   */
  @Override
  public Vote[] getPredictionVotes() {
    Attribute classAttribute = this.lastSeenInstance.dataset().classAttribute();
    double trueValue = this.lastSeenInstance.classValue();
    List<String> classAttributeValues = classAttribute.getAttributeValues();

    int trueNominalIndex = (int) trueValue;
    String trueNominalValue = classAttributeValues.get(trueNominalIndex);

    Vote[] votes = new Vote[classVotes.length + 3];
    votes[0] = new Vote("instance number",
        this.instanceIdentifier);
    votes[1] = new Vote("true class value",
        trueNominalValue);
    votes[2] = new Vote("predicted class value",
        classAttributeValues.get(Utils.maxIndex(classVotes)));

    for (int i = 0; i < classAttributeValues.size(); i++) {
      if (i < classVotes.length) {
        votes[2 + i] = new Vote("votes_" + classAttributeValues.get(i), classVotes[i]);
      } else {
        votes[2 + i] = new Vote("votes_" + classAttributeValues.get(i), 0);
      }
    }
    return votes;
  }

  public double getTotalWeightObserved() {
    return this.weightObserved.total();
  }

  public double getFractionCorrectlyClassified() {
    return this.weightObserved.total() > 0.0 ? this.weightCorrect.total()
        / this.weightObserved.total() : 0.0;
  }

  public double getKappaStatistic() {
    if (this.weightObserved.total() > 0.0) {
      double p0 = this.weightCorrect.total() / this.weightObserved.total();
      double pc = 0;
      for (int i = 0; i < this.numClasses; i++) {
        pc += (this.rowKappa[i].total() / this.weightObserved.total())
            * (this.columnKappa[i].total() / this.weightObserved.total());
      }
      return (p0 - pc) / (1 - pc);
    } else {
      return 0;
    }
  }

  public double getKappaTemporalStatistic() {
    if (this.weightObserved.total() > 0.0) {
      double p0 = this.weightCorrect.total() / this.weightObserved.total();
      double pc = this.weightCorrectNoChangeClassifier.total() / this.weightObserved.total();

      return (p0 - pc) / (1 - pc);
    } else {
      return 0;
    }
  }

  public double getFractionIncorrectlyClassified() {
    return 1.0 - getFractionCorrectlyClassified();
  }

  @Override
  public void getDescription(StringBuilder sb, int indent) {
    Measurement.getMeasurementsDescription(getPerformanceMeasurements(),
        sb, indent);
  }

}