| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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. |
| */ |
| |
| package org.apache.samoa.moa.classifiers.core.splitcriteria; |
| |
| import org.apache.samoa.moa.core.Utils; |
| |
| /** |
| * Class for computing splitting criteria using information gain with respect to distributions of class values for |
| * Multilabel data. The split criterion is used as a parameter on decision trees and decision stumps. |
| * |
| * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz) |
| * @author Jesse Read (jesse@tsc.uc3m.es) |
| * @version $Revision: 1 $ |
| */ |
| public class InfoGainSplitCriterionMultilabel extends InfoGainSplitCriterion { |
| |
| private static final long serialVersionUID = 1L; |
| |
| public static double computeEntropy(double[] dist) { |
| double entropy = 0.0; |
| double sum = 0.0; |
| for (double d : dist) { |
| sum += d; |
| } |
| if (sum > 0.0) { |
| for (double num : dist) { |
| double d = num / sum; |
| if (d > 0.0) { // TODO: how small can d be before log2 overflows? |
| entropy -= d * Utils.log2(d) + (1 - d) * Utils.log2(1 - d); // Extension to Multilabel |
| } |
| } |
| } |
| return sum > 0.0 ? entropy : 0.0; |
| } |
| } |