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 }