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.math3.stat.descriptive.rank;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.math3.exception.MathIllegalArgumentException;
22 import org.apache.commons.math3.exception.NullArgumentException;
23 import org.apache.commons.math3.stat.descriptive.AbstractStorelessUnivariateStatistic;
24 import org.apache.commons.math3.util.MathUtils;
25
26 /**
27 * Returns the maximum of the available values.
28 * <p>
29 * <ul>
30 * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
31 * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
32 * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
33 * the result is <code>Double.POSITIVE_INFINITY.</code></li>
34 * </ul></p>
35 * <p>
36 * <strong>Note that this implementation is not synchronized.</strong> If
37 * multiple threads access an instance of this class concurrently, and at least
38 * one of the threads invokes the <code>increment()</code> or
39 * <code>clear()</code> method, it must be synchronized externally.</p>
40 *
41 * @version $Id: Max.java 1416643 2012-12-03 19:37:14Z tn $
42 */
43 public class Max extends AbstractStorelessUnivariateStatistic implements Serializable {
44
45 /** Serializable version identifier */
46 private static final long serialVersionUID = -5593383832225844641L;
47
48 /** Number of values that have been added */
49 private long n;
50
51 /** Current value of the statistic */
52 private double value;
53
54 /**
55 * Create a Max instance
56 */
57 public Max() {
58 n = 0;
59 value = Double.NaN;
60 }
61
62 /**
63 * Copy constructor, creates a new {@code Max} identical
64 * to the {@code original}
65 *
66 * @param original the {@code Max} instance to copy
67 * @throws NullArgumentException if original is null
68 */
69 public Max(Max original) throws NullArgumentException {
70 copy(original, this);
71 }
72
73 /**
74 * {@inheritDoc}
75 */
76 @Override
77 public void increment(final double d) {
78 if (d > value || Double.isNaN(value)) {
79 value = d;
80 }
81 n++;
82 }
83
84 /**
85 * {@inheritDoc}
86 */
87 @Override
88 public void clear() {
89 value = Double.NaN;
90 n = 0;
91 }
92
93 /**
94 * {@inheritDoc}
95 */
96 @Override
97 public double getResult() {
98 return value;
99 }
100
101 /**
102 * {@inheritDoc}
103 */
104 public long getN() {
105 return n;
106 }
107
108 /**
109 * Returns the maximum of the entries in the specified portion of
110 * the input array, or <code>Double.NaN</code> if the designated subarray
111 * is empty.
112 * <p>
113 * Throws <code>MathIllegalArgumentException</code> if the array is null or
114 * the array index parameters are not valid.</p>
115 * <p>
116 * <ul>
117 * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
118 * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
119 * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
120 * the result is <code>Double.POSITIVE_INFINITY.</code></li>
121 * </ul></p>
122 *
123 * @param values the input array
124 * @param begin index of the first array element to include
125 * @param length the number of elements to include
126 * @return the maximum of the values or Double.NaN if length = 0
127 * @throws MathIllegalArgumentException if the array is null or the array index
128 * parameters are not valid
129 */
130 @Override
131 public double evaluate(final double[] values, final int begin, final int length)
132 throws MathIllegalArgumentException {
133 double max = Double.NaN;
134 if (test(values, begin, length)) {
135 max = values[begin];
136 for (int i = begin; i < begin + length; i++) {
137 if (!Double.isNaN(values[i])) {
138 max = (max > values[i]) ? max : values[i];
139 }
140 }
141 }
142 return max;
143 }
144
145 /**
146 * {@inheritDoc}
147 */
148 @Override
149 public Max copy() {
150 Max result = new Max();
151 // No try-catch or advertised exception because args are non-null
152 copy(this, result);
153 return result;
154 }
155
156 /**
157 * Copies source to dest.
158 * <p>Neither source nor dest can be null.</p>
159 *
160 * @param source Max to copy
161 * @param dest Max to copy to
162 * @throws NullArgumentException if either source or dest is null
163 */
164 public static void copy(Max source, Max dest)
165 throws NullArgumentException {
166 MathUtils.checkNotNull(source);
167 MathUtils.checkNotNull(dest);
168 dest.setData(source.getDataRef());
169 dest.n = source.n;
170 dest.value = source.value;
171 }
172 }