/*
* RapidMiner
*
* Copyright (C) 2001-2008 by Rapid-I and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapid-i.com
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see http://www.gnu.org/licenses/.
*/
package com.rapidminer.operator.learner.tree;
import com.rapidminer.example.set.SplittedExampleSet;
/**
* Calculates the accuracies for the given split if the children
* predict the majority classes.
*
* @author Ingo Mierswa
* @version $Id: AccuracyCriterion.java,v 1.5 2008/05/09 19:22:53 ingomierswa Exp $
*/
public class AccuracyCriterion extends AbstractCriterion {
private FrequencyCalculator calculator = new FrequencyCalculator();
public double getBenefit(SplittedExampleSet exampleSet) {
double sum = 0.0d;
for (int i = 0; i < exampleSet.getNumberOfSubsets(); i++) {
exampleSet.selectSingleSubset(i);
double[] partitionWeights = calculator.getLabelWeights(exampleSet);
int maxIndex = -1;
double maxValue = Double.NEGATIVE_INFINITY;
double currentSum = 0.0d;
for (int j = 0; j < partitionWeights.length; j++) {
if (partitionWeights[j] > maxValue) {
maxIndex = j;
maxValue = partitionWeights[j];
}
currentSum += partitionWeights[j];
}
sum += partitionWeights[maxIndex] / currentSum;
}
return sum;
}
public boolean supportsIncrementalCalculation() {
return true;
}
public double getIncrementalBenefit() {
int maxIndex = -1;
double maxValue = Double.NEGATIVE_INFINITY;
double currentSum = 0.0d;
for (int j = 0; j < leftLabelWeights.length; j++) {
if (leftLabelWeights[j] > maxValue) {
maxIndex = j;
maxValue = leftLabelWeights[j];
}
currentSum += leftLabelWeights[j];
}
double sum = leftLabelWeights[maxIndex] / currentSum;
maxIndex = -1;
maxValue = Double.NEGATIVE_INFINITY;
currentSum = 0.0d;
for (int j = 0; j < rightLabelWeights.length; j++) {
if (rightLabelWeights[j] > maxValue) {
maxIndex = j;
maxValue = rightLabelWeights[j];
}
currentSum += rightLabelWeights[j];
}
return sum + rightLabelWeights[maxIndex] / currentSum;
}
}