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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  package org.apache.commons.math.stat.descriptive.moment;
18  
19  import java.io.Serializable;
20  import java.util.Arrays;
21  
22  import org.apache.commons.math.DimensionMismatchException;
23  
24  /**
25   * Returns the arithmetic mean of the available vectors.
26   * @since 1.2
27   * @version $Revision: 780645 $ $Date: 2009-06-01 09:24:19 -0400 (Mon, 01 Jun 2009) $
28   */
29  public class VectorialMean implements Serializable {
30  
31      /** Serializable version identifier */
32      private static final long serialVersionUID = 8223009086481006892L;
33  
34      /** Means for each component. */
35      private Mean[] means;
36  
37      /** Constructs a VectorialMean.
38       * @param dimension vectors dimension
39       */
40      public VectorialMean(int dimension) {
41          means = new Mean[dimension];
42          for (int i = 0; i < dimension; ++i) {
43              means[i] = new Mean();
44          }
45      }
46  
47      /**
48       * Add a new vector to the sample.
49       * @param v vector to add
50       * @exception DimensionMismatchException if the vector does not have the right dimension
51       */
52      public void increment(double[] v) throws DimensionMismatchException {
53          if (v.length != means.length) {
54              throw new DimensionMismatchException(v.length, means.length);
55          }
56          for (int i = 0; i < v.length; ++i) {
57              means[i].increment(v[i]);
58          }
59      }
60  
61      /**
62       * Get the mean vector.
63       * @return mean vector
64       */
65      public double[] getResult() {
66          double[] result = new double[means.length];
67          for (int i = 0; i < result.length; ++i) {
68              result[i] = means[i].getResult();
69          }
70          return result;
71      }
72  
73      /**
74       * Get the number of vectors in the sample.
75       * @return number of vectors in the sample
76       */
77      public long getN() {
78          return (means.length == 0) ? 0 : means[0].getN();
79      }
80  
81      /** {@inheritDoc} */
82      @Override
83      public int hashCode() {
84          final int prime = 31;
85          int result = 1;
86          result = prime * result + Arrays.hashCode(means);
87          return result;
88      }
89  
90      /** {@inheritDoc} */
91      @Override
92      public boolean equals(Object obj) {
93          if (this == obj)
94              return true;
95          if (obj == null)
96              return false;
97          if (!(obj instanceof VectorialMean))
98              return false;
99          VectorialMean other = (VectorialMean) obj;
100         if (!Arrays.equals(means, other.means))
101             return false;
102         return true;
103     }
104 
105 }