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 */
017package org.apache.commons.math4.legacy.stat.descriptive.rank;
018
019import org.apache.commons.math4.legacy.exception.MathIllegalArgumentException;
020import org.apache.commons.math4.legacy.exception.NullArgumentException;
021import org.apache.commons.math4.legacy.stat.descriptive.AbstractStorelessUnivariateStatistic;
022import org.apache.commons.math4.legacy.core.MathArrays;
023
024/**
025 * Returns the maximum of the available values.
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>
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 */
038public class Max extends AbstractStorelessUnivariateStatistic {
039    /** Number of values that have been added. */
040    private long n;
041
042    /** Current value of the statistic. */
043    private double value;
044
045    /**
046     * Create a Max instance.
047     */
048    public Max() {
049        n = 0;
050        value = Double.NaN;
051    }
052
053    /**
054     * Copy constructor, creates a new {@code Max} identical
055     * to the {@code original}.
056     *
057     * @param original the {@code Max} instance to copy
058     * @throws NullArgumentException if original is null
059     */
060    public Max(Max original) throws NullArgumentException {
061        copy(original, this);
062    }
063
064    /**
065     * {@inheritDoc}
066     */
067    @Override
068    public void increment(final double d) {
069        if (d > value || Double.isNaN(value)) {
070            value = d;
071        }
072        n++;
073    }
074
075    /**
076     * {@inheritDoc}
077     */
078    @Override
079    public void clear() {
080        value = Double.NaN;
081        n = 0;
082    }
083
084    /**
085     * {@inheritDoc}
086     */
087    @Override
088    public double getResult() {
089        return value;
090    }
091
092    /**
093     * {@inheritDoc}
094     */
095    @Override
096    public long getN() {
097        return n;
098    }
099
100    /**
101     * Returns the maximum of the entries in the specified portion of
102     * the input array, or <code>Double.NaN</code> if the designated subarray
103     * is empty.
104     * <p>
105     * Throws <code>MathIllegalArgumentException</code> if the array is null or
106     * the array index parameters are not valid.</p>
107     * <ul>
108     * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
109     * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
110     * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
111     * the result is <code>Double.POSITIVE_INFINITY.</code></li>
112     * </ul>
113     *
114     * @param values the input array
115     * @param begin index of the first array element to include
116     * @param length the number of elements to include
117     * @return the maximum of the values or Double.NaN if length = 0
118     * @throws MathIllegalArgumentException if the array is null or the array index
119     *  parameters are not valid
120     */
121    @Override
122    public double evaluate(final double[] values, final int begin, final int length)
123        throws MathIllegalArgumentException {
124
125        double max = Double.NaN;
126        if (MathArrays.verifyValues(values, begin, length)) {
127            max = values[begin];
128            for (int i = begin; i < begin + length; i++) {
129                if (!Double.isNaN(values[i])) {
130                    max = (max > values[i]) ? max : values[i];
131                }
132            }
133        }
134        return max;
135    }
136
137    /**
138     * {@inheritDoc}
139     */
140    @Override
141    public Max copy() {
142        Max result = new Max();
143        // No try-catch or advertised exception because args are non-null
144        copy(this, result);
145        return result;
146    }
147
148    /**
149     * Copies source to dest.
150     * <p>Neither source nor dest can be null.</p>
151     *
152     * @param source Max to copy
153     * @param dest Max to copy to
154     * @throws NullArgumentException if either source or dest is null
155     */
156    public static void copy(Max source, Max dest)
157        throws NullArgumentException {
158        NullArgumentException.check(source);
159        NullArgumentException.check(dest);
160        dest.n = source.n;
161        dest.value = source.value;
162    }
163}