| package com.yahoo.labs.samoa.moa.classifiers.core.splitcriteria; |
| |
| /* |
| * #%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% |
| */ |
| |
| import com.yahoo.labs.samoa.moa.core.ObjectRepository; |
| import com.yahoo.labs.samoa.moa.core.Utils; |
| import com.yahoo.labs.samoa.moa.options.AbstractOptionHandler; |
| import com.yahoo.labs.samoa.moa.tasks.TaskMonitor; |
| |
| /** |
| * Class for computing splitting criteria using Gini with respect to |
| * distributions of class values. The split criterion is used as a parameter on |
| * decision trees and decision stumps. |
| * |
| * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz) |
| * @version $Revision: 7 $ |
| */ |
| public class GiniSplitCriterion extends AbstractOptionHandler implements |
| SplitCriterion { |
| |
| private static final long serialVersionUID = 1L; |
| |
| @Override |
| 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; |
| } |
| |
| @Override |
| public double getRangeOfMerit(double[] preSplitDist) { |
| return 1.0; |
| } |
| |
| public static double computeGini(double[] dist, double distSumOfWeights) { |
| double gini = 1.0; |
| for (double aDist : dist) { |
| double relFreq = aDist / distSumOfWeights; |
| gini -= relFreq * relFreq; |
| } |
| return gini; |
| } |
| |
| public static double computeGini(double[] dist) { |
| return computeGini(dist, Utils.sum(dist)); |
| } |
| |
| @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 |
| } |
| } |