    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.summary;
    018
    019    import java.io.Serializable;
    020
    021    import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
    022
    023
    024    /**
    025      * Returns the sum of the available values.
    026     * <p>
    027     * If there are no values in the dataset, or any of the values are
    028     * <code>NaN</code>, then <code>NaN</code> is returned.</p>
    029     * <p>
    030     * <strong>Note that this implementation is not synchronized.</strong> If
    031     * multiple threads access an instance of this class concurrently, and at least
    032     * one of the threads invokes the <code>increment()</code> or
    033     * <code>clear()</code> method, it must be synchronized externally.</p>
    034     *
    035     * @version $Revision: 1006299 $ $Date: 2010-10-10 16:47:17 +0200 (dim. 10 oct. 2010) $
    036     */
    037    public class Sum extends AbstractStorelessUnivariateStatistic implements Serializable {
    038
    039        /** Serializable version identifier */
    040        private static final long serialVersionUID = -8231831954703408316L;
    041
    042        /** */
    043        private long n;
    044
    045        /**
    046         * The currently running sum.
    047         */
    048        private double value;
    049
    050        /**
    051         * Create a Sum instance
    052         */
    053        public Sum() {
    054            n = 0;
    055            value = Double.NaN;
    056        }
    057
    058        /**
    059         * Copy constructor, creates a new {@code Sum} identical
    060         * to the {@code original}
    061         *
    062         * @param original the {@code Sum} instance to copy
    063         */
    064        public Sum(Sum original) {
    065            copy(original, this);
    066        }
    067
    068        /**
    069         * {@inheritDoc}
    070         */
    071        @Override
    072        public void increment(final double d) {
    073            if (n == 0) {
    074                value = d;
    075            } else {
    076                value += d;
    077            }
    078            n++;
    079        }
    080
    081        /**
    082         * {@inheritDoc}
    083         */
    084        @Override
    085        public double getResult() {
    086            return value;
    087        }
    088
    089        /**
    090         * {@inheritDoc}
    091         */
    092        public long getN() {
    093            return n;
    094        }
    095
    096        /**
    097         * {@inheritDoc}
    098         */
    099        @Override
    100        public void clear() {
    101            value = Double.NaN;
    102            n = 0;
    103        }
    104
    105        /**
    106         * The sum of the entries in the specified portion of
    107         * the input array, or <code>Double.NaN</code> if the designated subarray
    108         * is empty.
    109         * <p>
    110         * Throws <code>IllegalArgumentException</code> if the array is null.</p>
    111         *
    112         * @param values the input array
    113         * @param begin index of the first array element to include
    114         * @param length the number of elements to include
    115         * @return the sum of the values or Double.NaN if length = 0
    116         * @throws IllegalArgumentException if the array is null or the array index
    117         *  parameters are not valid
    118         */
    119        @Override
    120        public double evaluate(final double[] values, final int begin, final int length) {
    121            double sum = Double.NaN;
    122            if (test(values, begin, length)) {
    123                sum = 0.0;
    124                for (int i = begin; i < begin + length; i++) {
    125                    sum += values[i];
    126                }
    127            }
    128            return sum;
    129        }
    130
    131        /**
    132         * The weighted sum of the entries in the specified portion of
    133         * the input array, or <code>Double.NaN</code> if the designated subarray
    134         * is empty.
    135         * <p>
    136         * Throws <code>IllegalArgumentException</code> if any of the following are true:
    137         * <ul><li>the values array is null</li>
    138         *     <li>the weights array is null</li>
    139         *     <li>the weights array does not have the same length as the values array</li>
    140         *     <li>the weights array contains one or more infinite values</li>
    141         *     <li>the weights array contains one or more NaN values</li>
    142         *     <li>the weights array contains negative values</li>
    143         *     <li>the start and length arguments do not determine a valid array</li>
    144         * </ul></p>
    145         * <p>
    146         * Uses the formula, <pre>
    147         *    weighted sum = &Sigma;(values[i] * weights[i])
    148         * </pre></p>
    149         *
    150         * @param values the input array
    151         * @param weights the weights array
    152         * @param begin index of the first array element to include
    153         * @param length the number of elements to include
    154         * @return the sum of the values or Double.NaN if length = 0
    155         * @throws IllegalArgumentException if the parameters are not valid
    156         * @since 2.1
    157         */
    158        public double evaluate(final double[] values, final double[] weights,
    159                               final int begin, final int length) {
    160            double sum = Double.NaN;
    161            if (test(values, weights, begin, length)) {
    162                sum = 0.0;
    163                for (int i = begin; i < begin + length; i++) {
    164                    sum += values[i] * weights[i];
    165                }
    166            }
    167            return sum;
    168        }
    169
    170        /**
    171         * The weighted sum of the entries in the the input array.
    172         * <p>
    173         * Throws <code>IllegalArgumentException</code> if any of the following are true:
    174         * <ul><li>the values array is null</li>
    175         *     <li>the weights array is null</li>
    176         *     <li>the weights array does not have the same length as the values array</li>
    177         *     <li>the weights array contains one or more infinite values</li>
    178         *     <li>the weights array contains one or more NaN values</li>
    179         *     <li>the weights array contains negative values</li>
    180         * </ul></p>
    181         * <p>
    182         * Uses the formula, <pre>
    183         *    weighted sum = &Sigma;(values[i] * weights[i])
    184         * </pre></p>
    185         *
    186         * @param values the input array
    187         * @param weights the weights array
    188         * @return the sum of the values or Double.NaN if length = 0
    189         * @throws IllegalArgumentException if the parameters are not valid
    190         * @since 2.1
    191         */
    192        public double evaluate(final double[] values, final double[] weights) {
    193            return evaluate(values, weights, 0, values.length);
    194        }
    195
    196        /**
    197         * {@inheritDoc}
    198         */
    199        @Override
    200        public Sum copy() {
    201            Sum result = new Sum();
    202            copy(this, result);
    203            return result;
    204        }
    205
    206        /**
    207         * Copies source to dest.
    208         * <p>Neither source nor dest can be null.</p>
    209         *
    210         * @param source Sum to copy
    211         * @param dest Sum to copy to
    212         * @throws NullPointerException if either source or dest is null
    213         */
    214        public static void copy(Sum source, Sum dest) {
    215            dest.setData(source.getDataRef());
    216            dest.n = source.n;
    217            dest.value = source.value;
    218        }
    219
    220    }