moa.classifiers.meta.OzaBag.java Source code

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Here is the source code for moa.classifiers.meta.OzaBag.java

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/*
 *    OzaBag.java
 *    Copyright (C) 2007 University of Waikato, Hamilton, New Zealand
 *    @author Richard Kirkby (rkirkby@cs.waikato.ac.nz)
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 3 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program. If not, see <http://www.gnu.org/licenses/>.
 *    
 */
package moa.classifiers.meta;

import moa.classifiers.AbstractClassifier;
import moa.classifiers.Classifier;
import weka.core.Instance;

import moa.core.DoubleVector;
import moa.core.Measurement;
import moa.core.MiscUtils;
import moa.options.ClassOption;
import moa.options.IntOption;

/**
 * Incremental on-line bagging of Oza and Russell.
 *
 * <p>Oza and Russell developed online versions of bagging and boosting for
 * Data Streams. They show how the process of sampling bootstrap replicates
 * from training data can be simulated in a data stream context. They observe
 * that the probability that any individual example will be chosen for a
 * replicate tends to a Poisson(1) distribution.</p>
 *
 * <p>[OR] N. Oza and S. Russell. Online bagging and boosting.
 * In Arti?cial Intelligence and Statistics 2001, pages 105112.
 * Morgan Kaufmann, 2001.</p>
 *
 * <p>Parameters:</p> <ul>
 * <li>-l : Classi?er to train</li>
 * <li>-s : The number of models in the bag</li> </ul>
 *
 * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz)
 * @version $Revision: 7 $
 */
public class OzaBag extends AbstractClassifier {

    @Override
    public String getPurposeString() {
        return "Incremental on-line bagging of Oza and Russell.";
    }

    private static final long serialVersionUID = 1L;

    public ClassOption baseLearnerOption = new ClassOption("baseLearner", 'l', "Classifier to train.",
            Classifier.class, "trees.HoeffdingTree");

    public IntOption ensembleSizeOption = new IntOption("ensembleSize", 's', "The number of models in the bag.", 10,
            1, Integer.MAX_VALUE);

    protected Classifier[] ensemble;

    @Override
    public void resetLearningImpl() {
        this.ensemble = new Classifier[this.ensembleSizeOption.getValue()];
        Classifier baseLearner = (Classifier) getPreparedClassOption(this.baseLearnerOption);
        baseLearner.resetLearning();
        for (int i = 0; i < this.ensemble.length; i++) {
            this.ensemble[i] = baseLearner.copy();
        }
    }

    @Override
    public void trainOnInstanceImpl(Instance inst) {
        for (int i = 0; i < this.ensemble.length; i++) {
            int k = MiscUtils.poisson(1.0, this.classifierRandom);
            if (k > 0) {
                Instance weightedInst = (Instance) inst.copy();
                weightedInst.setWeight(inst.weight() * k);
                this.ensemble[i].trainOnInstance(weightedInst);
            }
        }
    }

    @Override
    public double[] getVotesForInstance(Instance inst) {
        DoubleVector combinedVote = new DoubleVector();
        for (int i = 0; i < this.ensemble.length; i++) {
            DoubleVector vote = new DoubleVector(this.ensemble[i].getVotesForInstance(inst));
            if (vote.sumOfValues() > 0.0) {
                vote.normalize();
                combinedVote.addValues(vote);
            }
        }
        return combinedVote.getArrayRef();
    }

    @Override
    public boolean isRandomizable() {
        return true;
    }

    @Override
    public void getModelDescription(StringBuilder out, int indent) {
        // TODO Auto-generated method stub
    }

    @Override
    protected Measurement[] getModelMeasurementsImpl() {
        return new Measurement[] {
                new Measurement("ensemble size", this.ensemble != null ? this.ensemble.length : 0) };
    }

    @Override
    public Classifier[] getSubClassifiers() {
        return this.ensemble.clone();
    }
}