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.rank;
018
019 import java.io.Serializable;
020
021 import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
022
023 /**
024 * Returns the maximum of the available values.
025 * <p>
026 * <ul>
027 * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
028 * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
029 * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
030 * the result is <code>Double.POSITIVE_INFINITY.</code></li>
031 * </ul></p>
032 * <p>
033 * <strong>Note that this implementation is not synchronized.</strong> If
034 * multiple threads access an instance of this class concurrently, and at least
035 * one of the threads invokes the <code>increment()</code> or
036 * <code>clear()</code> method, it must be synchronized externally.</p>
037 *
038 * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $
039 */
040 public class Max extends AbstractStorelessUnivariateStatistic implements Serializable {
041
042 /** Serializable version identifier */
043 private static final long serialVersionUID = -5593383832225844641L;
044
045 /** Number of values that have been added */
046 private long n;
047
048 /** Current value of the statistic */
049 private double value;
050
051 /**
052 * Create a Max instance
053 */
054 public Max() {
055 n = 0;
056 value = Double.NaN;
057 }
058
059 /**
060 * Copy constructor, creates a new {@code Max} identical
061 * to the {@code original}
062 *
063 * @param original the {@code Max} instance to copy
064 */
065 public Max(Max original) {
066 copy(original, this);
067 }
068
069 /**
070 * {@inheritDoc}
071 */
072 @Override
073 public void increment(final double d) {
074 if (d > value || Double.isNaN(value)) {
075 value = d;
076 }
077 n++;
078 }
079
080 /**
081 * {@inheritDoc}
082 */
083 @Override
084 public void clear() {
085 value = Double.NaN;
086 n = 0;
087 }
088
089 /**
090 * {@inheritDoc}
091 */
092 @Override
093 public double getResult() {
094 return value;
095 }
096
097 /**
098 * {@inheritDoc}
099 */
100 public long getN() {
101 return n;
102 }
103
104 /**
105 * Returns the maximum of the entries in the specified portion of
106 * the input array, or <code>Double.NaN</code> if the designated subarray
107 * is empty.
108 * <p>
109 * Throws <code>IllegalArgumentException</code> if the array is null or
110 * the array index parameters are not valid.</p>
111 * <p>
112 * <ul>
113 * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
114 * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
115 * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
116 * the result is <code>Double.POSITIVE_INFINITY.</code></li>
117 * </ul></p>
118 *
119 * @param values the input array
120 * @param begin index of the first array element to include
121 * @param length the number of elements to include
122 * @return the maximum of the values or Double.NaN if length = 0
123 * @throws IllegalArgumentException if the array is null or the array index
124 * parameters are not valid
125 */
126 @Override
127 public double evaluate(final double[] values, final int begin, final int length) {
128 double max = Double.NaN;
129 if (test(values, begin, length)) {
130 max = values[begin];
131 for (int i = begin; i < begin + length; i++) {
132 if (!Double.isNaN(values[i])) {
133 max = (max > values[i]) ? max : values[i];
134 }
135 }
136 }
137 return max;
138 }
139
140 /**
141 * {@inheritDoc}
142 */
143 @Override
144 public Max copy() {
145 Max result = new Max();
146 copy(this, result);
147 return result;
148 }
149
150 /**
151 * Copies source to dest.
152 * <p>Neither source nor dest can be null.</p>
153 *
154 * @param source Max to copy
155 * @param dest Max to copy to
156 * @throws NullPointerException if either source or dest is null
157 */
158 public static void copy(Max source, Max dest) {
159 dest.n = source.n;
160 dest.value = source.value;
161 }
162 }