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.math3.stat.descriptive.rank;
018
019 import java.io.Serializable;
020
021 import org.apache.commons.math3.exception.MathIllegalArgumentException;
022 import org.apache.commons.math3.exception.NullArgumentException;
023 import org.apache.commons.math3.stat.descriptive.AbstractStorelessUnivariateStatistic;
024 import org.apache.commons.math3.util.MathUtils;
025
026 /**
027 * Returns the minimum of the available values.
028 * <p>
029 * <ul>
030 * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
031 * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
032 * <li>If any of the values equals <code>Double.NEGATIVE_INFINITY</code>,
033 * the result is <code>Double.NEGATIVE_INFINITY.</code></li>
034 * </ul></p>
035 * <p>
036 * <strong>Note that this implementation is not synchronized.</strong> If
037 * multiple threads access an instance of this class concurrently, and at least
038 * one of the threads invokes the <code>increment()</code> or
039 * <code>clear()</code> method, it must be synchronized externally.</p>
040 *
041 * @version $Id: Min.java 1416643 2012-12-03 19:37:14Z tn $
042 */
043 public class Min extends AbstractStorelessUnivariateStatistic implements Serializable {
044
045 /** Serializable version identifier */
046 private static final long serialVersionUID = -2941995784909003131L;
047
048 /**Number of values that have been added */
049 private long n;
050
051 /**Current value of the statistic */
052 private double value;
053
054 /**
055 * Create a Min instance
056 */
057 public Min() {
058 n = 0;
059 value = Double.NaN;
060 }
061
062 /**
063 * Copy constructor, creates a new {@code Min} identical
064 * to the {@code original}
065 *
066 * @param original the {@code Min} instance to copy
067 * @throws NullArgumentException if original is null
068 */
069 public Min(Min original) throws NullArgumentException {
070 copy(original, this);
071 }
072
073 /**
074 * {@inheritDoc}
075 */
076 @Override
077 public void increment(final double d) {
078 if (d < value || Double.isNaN(value)) {
079 value = d;
080 }
081 n++;
082 }
083
084 /**
085 * {@inheritDoc}
086 */
087 @Override
088 public void clear() {
089 value = Double.NaN;
090 n = 0;
091 }
092
093 /**
094 * {@inheritDoc}
095 */
096 @Override
097 public double getResult() {
098 return value;
099 }
100
101 /**
102 * {@inheritDoc}
103 */
104 public long getN() {
105 return n;
106 }
107
108 /**
109 * Returns the minimum 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.NEGATIVE_INFINITY</code>,
120 * the result is <code>Double.NEGATIVE_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 minimum 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 min = Double.NaN;
134 if (test(values, begin, length)) {
135 min = values[begin];
136 for (int i = begin; i < begin + length; i++) {
137 if (!Double.isNaN(values[i])) {
138 min = (min < values[i]) ? min : values[i];
139 }
140 }
141 }
142 return min;
143 }
144
145 /**
146 * {@inheritDoc}
147 */
148 @Override
149 public Min copy() {
150 Min result = new Min();
151 // No try-catch or advertised exception - 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 Min to copy
161 * @param dest Min to copy to
162 * @throws NullArgumentException if either source or dest is null
163 */
164 public static void copy(Min source, Min 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 }