1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package org.apache.commons.math4.legacy.ml.clustering; 19 20 import java.util.ArrayList; 21 import java.util.List; 22 23 /** 24 * Cluster holding a set of {@link Clusterable} points. 25 * @param <T> the type of points that can be clustered 26 * @since 3.2 27 */ 28 public class Cluster<T extends Clusterable> { 29 30 /** The points contained in this cluster. */ 31 private final List<T> points; 32 33 /** 34 * Build a cluster centered at a specified point. 35 */ 36 public Cluster() { 37 points = new ArrayList<>(); 38 } 39 40 /** 41 * Add a point to this cluster. 42 * @param point point to add 43 */ 44 public void addPoint(final T point) { 45 points.add(point); 46 } 47 48 /** 49 * Get the points contained in the cluster. 50 * @return points contained in the cluster 51 */ 52 public List<T> getPoints() { 53 return points; 54 } 55 56 /** 57 * Computes the centroid of the cluster. 58 * 59 * @return the centroid for the cluster, or {@code null} if the 60 * cluster does not contain any points. 61 */ 62 public Clusterable centroid() { 63 if (points.isEmpty()) { 64 return null; 65 } else { 66 final int dimension = points.get(0).getPoint().length; 67 final double[] centroid = new double[dimension]; 68 for (final T p : points) { 69 final double[] point = p.getPoint(); 70 for (int i = 0; i < centroid.length; i++) { 71 centroid[i] += point[i]; 72 } 73 } 74 for (int i = 0; i < centroid.length; i++) { 75 centroid[i] /= points.size(); 76 } 77 return new DoublePoint(centroid); 78 } 79 } 80 }