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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.math.stat.clustering;
19  
20  import java.io.Serializable;
21  import java.util.Collection;
22  
23  import org.apache.commons.math.util.MathUtils;
24  
25  /**
26   * A simple implementation of {@link Clusterable} for points with integer coordinates.
27   * @version $Revision: 795984 $ $Date: 2009-07-20 16:13:24 -0400 (Mon, 20 Jul 2009) $
28   * @since 2.0
29   */
30  public class EuclideanIntegerPoint implements Clusterable<EuclideanIntegerPoint>, Serializable {
31  
32      /** Serializable version identifier. */
33      private static final long serialVersionUID = 3946024775784901369L;
34  
35      /** Point coordinates. */
36      private final int[] point;
37  
38      /**
39       * Build an instance wrapping an integer array.
40       * <p>The wrapped array is referenced, it is <em>not</em> copied.</p>
41       * @param point the n-dimensional point in integer space
42       */
43      public EuclideanIntegerPoint(final int[] point) {
44          this.point = point;
45      }
46  
47      /**
48       * Get the n-dimensional point in integer space.
49       * @return a reference (not a copy!) to the wrapped array
50       */
51      public int[] getPoint() {
52          return point;
53      }
54  
55      /** {@inheritDoc} */
56      public double distanceFrom(final EuclideanIntegerPoint p) {
57          return MathUtils.distance(point, p.getPoint());
58      }
59  
60      /** {@inheritDoc} */
61      public EuclideanIntegerPoint centroidOf(final Collection<EuclideanIntegerPoint> points) {
62          int[] centroid = new int[getPoint().length];
63          for (EuclideanIntegerPoint p : points) {
64              for (int i = 0; i < centroid.length; i++) {
65                  centroid[i] += p.getPoint()[i];
66              }
67          }
68          for (int i = 0; i < centroid.length; i++) {
69              centroid[i] /= points.size();
70          }
71          return new EuclideanIntegerPoint(centroid);
72      }
73  
74      /** {@inheritDoc} */
75      @Override
76      public boolean equals(final Object other) {
77          if (!(other instanceof EuclideanIntegerPoint)) {
78              return false;
79          }
80          final int[] otherPoint = ((EuclideanIntegerPoint) other).getPoint();
81          if (point.length != otherPoint.length) {
82              return false;
83          }
84          for (int i = 0; i < point.length; i++) {
85              if (point[i] != otherPoint[i]) {
86                  return false;
87              }
88          }
89          return true;
90      }
91  
92      /** {@inheritDoc} */
93      @Override
94      public int hashCode() {
95          int hashCode = 0;
96          for (Integer i : point) {
97              hashCode += i.hashCode() * 13 + 7;
98          }
99          return hashCode;
100     }
101 
102 }