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 }