/*
* GiniSplitCriterion.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 2 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, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
package tr.gov.ulakbim.jDenetX.classifiers.splits;
import tr.gov.ulakbim.jDenetX.core.ObjectRepository;
import tr.gov.ulakbim.jDenetX.options.AbstractOptionHandler;
import tr.gov.ulakbim.jDenetX.tasks.TaskMonitor;
import weka.core.Utils;
public class GiniSplitCriterion extends AbstractOptionHandler implements
SplitCriterion {
private static final long serialVersionUID = 1L;
public double getMeritOfSplit(double[] preSplitDist,
double[][] postSplitDists) {
double totalWeight = 0.0;
double[] distWeights = new double[postSplitDists.length];
for (int i = 0; i < postSplitDists.length; i++) {
distWeights[i] = Utils.sum(postSplitDists[i]);
totalWeight += distWeights[i];
}
double gini = 0.0;
for (int i = 0; i < postSplitDists.length; i++) {
gini += (distWeights[i] / totalWeight)
* computeGini(postSplitDists[i], distWeights[i]);
}
return 1.0 - gini;
}
public double getRangeOfMerit(double[] preSplitDist) {
return 1.0;
}
public static double computeGini(double[] dist, double distSumOfWeights) {
double gini = 1.0;
for (int i = 0; i < dist.length; i++) {
double relFreq = dist[i] / distSumOfWeights;
gini -= relFreq * relFreq;
}
return gini;
}
public static double computeGini(double[] dist) {
return computeGini(dist, Utils.sum(dist));
}
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
}
}