    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 minimum 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.NEGATIVE_INFINITY</code>,
    030     * the result is <code>Double.NEGATIVE_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: 1006299 $ $Date: 2010-10-10 16:47:17 +0200 (dim. 10 oct. 2010) $
    039     */
    040    public class Min extends AbstractStorelessUnivariateStatistic implements Serializable {
    041
    042        /** Serializable version identifier */
    043        private static final long serialVersionUID = -2941995784909003131L;
    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 Min instance
    053         */
    054        public Min() {
    055            n = 0;
    056            value = Double.NaN;
    057        }
    058
    059        /**
    060         * Copy constructor, creates a new {@code Min} identical
    061         * to the {@code original}
    062         *
    063         * @param original the {@code Min} instance to copy
    064         */
    065        public Min(Min 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 minimum 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.NEGATIVE_INFINITY</code>,
    116         * the result is <code>Double.NEGATIVE_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 minimum 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 min = Double.NaN;
    129            if (test(values, begin, length)) {
    130                min = values[begin];
    131                for (int i = begin; i < begin + length; i++) {
    132                    if (!Double.isNaN(values[i])) {
    133                        min = (min < values[i]) ? min : values[i];
    134                    }
    135                }
    136            }
    137            return min;
    138        }
    139
    140        /**
    141         * {@inheritDoc}
    142         */
    143        @Override
    144        public Min copy() {
    145            Min result = new Min();
    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 Min to copy
    155         * @param dest Min to copy to
    156         * @throws NullPointerException if either source or dest is null
    157         */
    158        public static void copy(Min source, Min dest) {
    159            dest.setData(source.getDataRef());
    160            dest.n = source.n;
    161            dest.value = source.value;
    162        }
    163    }