001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.math.stat.descriptive.moment;
018
019 import java.io.Serializable;
020 import java.util.Arrays;
021
022 import org.apache.commons.math.DimensionMismatchException;
023
024 /**
025 * Returns the arithmetic mean of the available vectors.
026 * @since 1.2
027 * @version $Revision: 922714 $ $Date: 2010-03-14 02:35:14 +0100 (dim. 14 mars 2010) $
028 */
029 public class VectorialMean implements Serializable {
030
031 /** Serializable version identifier */
032 private static final long serialVersionUID = 8223009086481006892L;
033
034 /** Means for each component. */
035 private final Mean[] means;
036
037 /** Constructs a VectorialMean.
038 * @param dimension vectors dimension
039 */
040 public VectorialMean(int dimension) {
041 means = new Mean[dimension];
042 for (int i = 0; i < dimension; ++i) {
043 means[i] = new Mean();
044 }
045 }
046
047 /**
048 * Add a new vector to the sample.
049 * @param v vector to add
050 * @exception DimensionMismatchException if the vector does not have the right dimension
051 */
052 public void increment(double[] v) throws DimensionMismatchException {
053 if (v.length != means.length) {
054 throw new DimensionMismatchException(v.length, means.length);
055 }
056 for (int i = 0; i < v.length; ++i) {
057 means[i].increment(v[i]);
058 }
059 }
060
061 /**
062 * Get the mean vector.
063 * @return mean vector
064 */
065 public double[] getResult() {
066 double[] result = new double[means.length];
067 for (int i = 0; i < result.length; ++i) {
068 result[i] = means[i].getResult();
069 }
070 return result;
071 }
072
073 /**
074 * Get the number of vectors in the sample.
075 * @return number of vectors in the sample
076 */
077 public long getN() {
078 return (means.length == 0) ? 0 : means[0].getN();
079 }
080
081 /** {@inheritDoc} */
082 @Override
083 public int hashCode() {
084 final int prime = 31;
085 int result = 1;
086 result = prime * result + Arrays.hashCode(means);
087 return result;
088 }
089
090 /** {@inheritDoc} */
091 @Override
092 public boolean equals(Object obj) {
093 if (this == obj)
094 return true;
095 if (!(obj instanceof VectorialMean))
096 return false;
097 VectorialMean other = (VectorialMean) obj;
098 if (!Arrays.equals(means, other.means))
099 return false;
100 return true;
101 }
102
103 }