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.summary;
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    /**
028      * Returns the sum of the available values.
029     * <p>
030     * If there are no values in the dataset, then 0 is returned.
031     * If any of the values are
032     * <code>NaN</code>, then <code>NaN</code> is returned.</p>
033     * <p>
034     * <strong>Note that this implementation is not synchronized.</strong> If
035     * multiple threads access an instance of this class concurrently, and at least
036     * one of the threads invokes the <code>increment()</code> or
037     * <code>clear()</code> method, it must be synchronized externally.</p>
038     *
039     * @version $Id: Sum.java 1416643 2012-12-03 19:37:14Z tn $
040     */
041    public class Sum extends AbstractStorelessUnivariateStatistic implements Serializable {
042    
043        /** Serializable version identifier */
044        private static final long serialVersionUID = -8231831954703408316L;
045    
046        /** */
047        private long n;
048    
049        /**
050         * The currently running sum.
051         */
052        private double value;
053    
054        /**
055         * Create a Sum instance
056         */
057        public Sum() {
058            n = 0;
059            value = 0;
060        }
061    
062        /**
063         * Copy constructor, creates a new {@code Sum} identical
064         * to the {@code original}
065         *
066         * @param original the {@code Sum} instance to copy
067         * @throws NullArgumentException if original is null
068         */
069        public Sum(Sum original) throws NullArgumentException {
070            copy(original, this);
071        }
072    
073        /**
074         * {@inheritDoc}
075         */
076        @Override
077        public void increment(final double d) {
078            value += d;
079            n++;
080        }
081    
082        /**
083         * {@inheritDoc}
084         */
085        @Override
086        public double getResult() {
087            return value;
088        }
089    
090        /**
091         * {@inheritDoc}
092         */
093        public long getN() {
094            return n;
095        }
096    
097        /**
098         * {@inheritDoc}
099         */
100        @Override
101        public void clear() {
102            value = 0;
103            n = 0;
104        }
105    
106        /**
107         * The sum of the entries in the specified portion of
108         * the input array, or 0 if the designated subarray
109         * is empty.
110         * <p>
111         * Throws <code>MathIllegalArgumentException</code> if the array is null.</p>
112         *
113         * @param values the input array
114         * @param begin index of the first array element to include
115         * @param length the number of elements to include
116         * @return the sum of the values or 0 if length = 0
117         * @throws MathIllegalArgumentException if the array is null or the array index
118         *  parameters are not valid
119         */
120        @Override
121        public double evaluate(final double[] values, final int begin, final int length)
122        throws MathIllegalArgumentException {
123            double sum = Double.NaN;
124            if (test(values, begin, length, true)) {
125                sum = 0.0;
126                for (int i = begin; i < begin + length; i++) {
127                    sum += values[i];
128                }
129            }
130            return sum;
131        }
132    
133        /**
134         * The weighted sum of the entries in the specified portion of
135         * the input array, or 0 if the designated subarray
136         * is empty.
137         * <p>
138         * Throws <code>MathIllegalArgumentException</code> if any of the following are true:
139         * <ul><li>the values array is null</li>
140         *     <li>the weights array is null</li>
141         *     <li>the weights array does not have the same length as the values array</li>
142         *     <li>the weights array contains one or more infinite values</li>
143         *     <li>the weights array contains one or more NaN values</li>
144         *     <li>the weights array contains negative values</li>
145         *     <li>the start and length arguments do not determine a valid array</li>
146         * </ul></p>
147         * <p>
148         * Uses the formula, <pre>
149         *    weighted sum = &Sigma;(values[i] * weights[i])
150         * </pre></p>
151         *
152         * @param values the input array
153         * @param weights the weights array
154         * @param begin index of the first array element to include
155         * @param length the number of elements to include
156         * @return the sum of the values or 0 if length = 0
157         * @throws MathIllegalArgumentException if the parameters are not valid
158         * @since 2.1
159         */
160        public double evaluate(final double[] values, final double[] weights,
161            final int begin, final int length) throws MathIllegalArgumentException {
162            double sum = Double.NaN;
163            if (test(values, weights, begin, length, true)) {
164                sum = 0.0;
165                for (int i = begin; i < begin + length; i++) {
166                    sum += values[i] * weights[i];
167                }
168            }
169            return sum;
170        }
171    
172        /**
173         * The weighted sum of the entries in the the input array.
174         * <p>
175         * Throws <code>MathIllegalArgumentException</code> if any of the following are true:
176         * <ul><li>the values array is null</li>
177         *     <li>the weights array is null</li>
178         *     <li>the weights array does not have the same length as the values array</li>
179         *     <li>the weights array contains one or more infinite values</li>
180         *     <li>the weights array contains one or more NaN values</li>
181         *     <li>the weights array contains negative values</li>
182         * </ul></p>
183         * <p>
184         * Uses the formula, <pre>
185         *    weighted sum = &Sigma;(values[i] * weights[i])
186         * </pre></p>
187         *
188         * @param values the input array
189         * @param weights the weights array
190         * @return the sum of the values or Double.NaN if length = 0
191         * @throws MathIllegalArgumentException if the parameters are not valid
192         * @since 2.1
193         */
194        public double evaluate(final double[] values, final double[] weights)
195        throws MathIllegalArgumentException {
196            return evaluate(values, weights, 0, values.length);
197        }
198    
199        /**
200         * {@inheritDoc}
201         */
202        @Override
203        public Sum copy() {
204            Sum result = new Sum();
205            // No try-catch or advertised exception because args are valid
206            copy(this, result);
207            return result;
208        }
209    
210        /**
211         * Copies source to dest.
212         * <p>Neither source nor dest can be null.</p>
213         *
214         * @param source Sum to copy
215         * @param dest Sum to copy to
216         * @throws NullArgumentException if either source or dest is null
217         */
218        public static void copy(Sum source, Sum dest)
219            throws NullArgumentException {
220            MathUtils.checkNotNull(source);
221            MathUtils.checkNotNull(dest);
222            dest.setData(source.getDataRef());
223            dest.n = source.n;
224            dest.value = source.value;
225        }
226    
227    }