NominalAttributeClassObserver.java

package com.yahoo.labs.samoa.moa.classifiers.core.attributeclassobservers;

/*
 * #%L
 * SAMOA
 * %%
 *    Copyright (C) 2007 University of Waikato, Hamilton, New Zealand
 * %%
 * 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%
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import com.yahoo.labs.samoa.moa.classifiers.core.AttributeSplitSuggestion;
import com.yahoo.labs.samoa.moa.classifiers.core.conditionaltests.NominalAttributeBinaryTest;
import com.yahoo.labs.samoa.moa.classifiers.core.conditionaltests.NominalAttributeMultiwayTest;
import com.yahoo.labs.samoa.moa.classifiers.core.splitcriteria.SplitCriterion;
import com.yahoo.labs.samoa.moa.core.ObjectRepository;
import com.yahoo.labs.samoa.moa.tasks.TaskMonitor;
import com.yahoo.labs.samoa.moa.core.Utils;

import com.yahoo.labs.samoa.moa.core.AutoExpandVector;
import com.yahoo.labs.samoa.moa.core.DoubleVector;
import com.yahoo.labs.samoa.moa.options.AbstractOptionHandler;

/**
 * Class for observing the class data distribution for a nominal attribute.
 * This observer monitors the class distribution of a given attribute.
 * Used in naive Bayes and decision trees to monitor data statistics on leaves.
 *
 * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz)
 * @version $Revision: 7 $
 */
public class NominalAttributeClassObserver extends AbstractOptionHandler implements DiscreteAttributeClassObserver {

    private static final long serialVersionUID = 1L;

    protected double totalWeightObserved = 0.0;

    protected double missingWeightObserved = 0.0;

    public AutoExpandVector<DoubleVector> attValDistPerClass = new AutoExpandVector<>();

    @Override
    public void observeAttributeClass(double attVal, int classVal, double weight) {
        if (Utils.isMissingValue(attVal)) {
            this.missingWeightObserved += weight;
        } else {
            int attValInt = (int) attVal;
            DoubleVector valDist = this.attValDistPerClass.get(classVal);
            if (valDist == null) {
                valDist = new DoubleVector();
                this.attValDistPerClass.set(classVal, valDist);
            }
            valDist.addToValue(attValInt, weight);
        }
        this.totalWeightObserved += weight;
    }

    @Override
    public double probabilityOfAttributeValueGivenClass(double attVal,
            int classVal) {
        DoubleVector obs = this.attValDistPerClass.get(classVal);
        return obs != null ? (obs.getValue((int) attVal) + 1.0)
                / (obs.sumOfValues() + obs.numValues()) : 0.0;
    }

    public double totalWeightOfClassObservations() {
        return this.totalWeightObserved;
    }

    public double weightOfObservedMissingValues() {
        return this.missingWeightObserved;
    }

    @Override
    public AttributeSplitSuggestion getBestEvaluatedSplitSuggestion(
            SplitCriterion criterion, double[] preSplitDist, int attIndex,
            boolean binaryOnly) {
        AttributeSplitSuggestion bestSuggestion = null;
        int maxAttValsObserved = getMaxAttValsObserved();
        if (!binaryOnly) {
            double[][] postSplitDists = getClassDistsResultingFromMultiwaySplit(maxAttValsObserved);
            double merit = criterion.getMeritOfSplit(preSplitDist,
                    postSplitDists);
            bestSuggestion = new AttributeSplitSuggestion(
                    new NominalAttributeMultiwayTest(attIndex), postSplitDists,
                    merit);
        }
        for (int valIndex = 0; valIndex < maxAttValsObserved; valIndex++) {
            double[][] postSplitDists = getClassDistsResultingFromBinarySplit(valIndex);
            double merit = criterion.getMeritOfSplit(preSplitDist,
                    postSplitDists);
            if ((bestSuggestion == null) || (merit > bestSuggestion.merit)) {
                bestSuggestion = new AttributeSplitSuggestion(
                        new NominalAttributeBinaryTest(attIndex, valIndex),
                        postSplitDists, merit);
            }
        }
        return bestSuggestion;
    }

    public int getMaxAttValsObserved() {
        int maxAttValsObserved = 0;
        for (DoubleVector attValDist : this.attValDistPerClass) {
            if ((attValDist != null)
                    && (attValDist.numValues() > maxAttValsObserved)) {
                maxAttValsObserved = attValDist.numValues();
            }
        }
        return maxAttValsObserved;
    }

    public double[][] getClassDistsResultingFromMultiwaySplit(
            int maxAttValsObserved) {
        DoubleVector[] resultingDists = new DoubleVector[maxAttValsObserved];
        for (int i = 0; i < resultingDists.length; i++) {
            resultingDists[i] = new DoubleVector();
        }
        for (int i = 0; i < this.attValDistPerClass.size(); i++) {
            DoubleVector attValDist = this.attValDistPerClass.get(i);
            if (attValDist != null) {
                for (int j = 0; j < attValDist.numValues(); j++) {
                    resultingDists[j].addToValue(i, attValDist.getValue(j));
                }
            }
        }
        double[][] distributions = new double[maxAttValsObserved][];
        for (int i = 0; i < distributions.length; i++) {
            distributions[i] = resultingDists[i].getArrayRef();
        }
        return distributions;
    }

    public double[][] getClassDistsResultingFromBinarySplit(int valIndex) {
        DoubleVector equalsDist = new DoubleVector();
        DoubleVector notEqualDist = new DoubleVector();
        for (int i = 0; i < this.attValDistPerClass.size(); i++) {
            DoubleVector attValDist = this.attValDistPerClass.get(i);
            if (attValDist != null) {
                for (int j = 0; j < attValDist.numValues(); j++) {
                    if (j == valIndex) {
                        equalsDist.addToValue(i, attValDist.getValue(j));
                    } else {
                        notEqualDist.addToValue(i, attValDist.getValue(j));
                    }
                }
            }
        }
        return new double[][]{equalsDist.getArrayRef(),
                    notEqualDist.getArrayRef()};
    }

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

    @Override
    protected void prepareForUseImpl(TaskMonitor monitor, ObjectRepository repository) {
        // TODO Auto-generated method stub
    }

    @Override
    public void observeAttributeTarget(double attVal, double target) {
        throw new UnsupportedOperationException("Not supported yet.");
    }

}