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Commons Math example source code file (Sum.java)

This example Commons Math source code file (Sum.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Math tags/keywords

abstractstorelessunivariatestatistic, abstractstorelessunivariatestatistic, io, override, override, serializable, serializable, sum, sum

The Commons Math Sum.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math.stat.descriptive.summary;

import java.io.Serializable;

import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;


/**
  * Returns the sum of the available values.
 * <p>
 * If there are no values in the dataset, or any of the values are
 * <code>NaN, then NaN is returned.

* <p> * <strong>Note that this implementation is not synchronized. If * multiple threads access an instance of this class concurrently, and at least * one of the threads invokes the <code>increment() or * <code>clear() method, it must be synchronized externally.

* * @version $Revision: 917270 $ $Date: 2010-02-28 14:37:53 -0500 (Sun, 28 Feb 2010) $ */ public class Sum extends AbstractStorelessUnivariateStatistic implements Serializable { /** Serializable version identifier */ private static final long serialVersionUID = -8231831954703408316L; /** */ private long n; /** * The currently running sum. */ private double value; /** * Create a Sum instance */ public Sum() { n = 0; value = Double.NaN; } /** * Copy constructor, creates a new {@code Sum} identical * to the {@code original} * * @param original the {@code Sum} instance to copy */ public Sum(Sum original) { copy(original, this); } /** * {@inheritDoc} */ @Override public void increment(final double d) { if (n == 0) { value = d; } else { value += d; } n++; } /** * {@inheritDoc} */ @Override public double getResult() { return value; } /** * {@inheritDoc} */ public long getN() { return n; } /** * {@inheritDoc} */ @Override public void clear() { value = Double.NaN; n = 0; } /** * The sum of the entries in the specified portion of * the input array, or <code>Double.NaN if the designated subarray * is empty. * <p> * Throws <code>IllegalArgumentException if the array is null.

* * @param values the input array * @param begin index of the first array element to include * @param length the number of elements to include * @return the sum of the values or Double.NaN if length = 0 * @throws IllegalArgumentException if the array is null or the array index * parameters are not valid */ @Override public double evaluate(final double[] values, final int begin, final int length) { double sum = Double.NaN; if (test(values, begin, length)) { sum = 0.0; for (int i = begin; i < begin + length; i++) { sum += values[i]; } } return sum; } /** * The weighted sum of the entries in the specified portion of * the input array, or <code>Double.NaN if the designated subarray * is empty. * <p> * Throws <code>IllegalArgumentException if any of the following are true: * <ul>
  • the values array is null
  • * <li>the weights array is null * <li>the weights array does not have the same length as the values array * <li>the weights array contains one or more infinite values * <li>the weights array contains one or more NaN values * <li>the weights array contains negative values * <li>the start and length arguments do not determine a valid array * </ul>

    * <p> * Uses the formula, <pre> * weighted sum = Σ(values[i] * weights[i]) * </pre>

    * * @param values the input array * @param weights the weights array * @param begin index of the first array element to include * @param length the number of elements to include * @return the sum of the values or Double.NaN if length = 0 * @throws IllegalArgumentException if the parameters are not valid * @since 2.1 */ public double evaluate(final double[] values, final double[] weights, final int begin, final int length) { double sum = Double.NaN; if (test(values, weights, begin, length)) { sum = 0.0; for (int i = begin; i < begin + length; i++) { sum += values[i] * weights[i]; } } return sum; } /** * The weighted sum of the entries in the the input array. * <p> * Throws <code>IllegalArgumentException if any of the following are true: * <ul>
  • the values array is null
  • * <li>the weights array is null * <li>the weights array does not have the same length as the values array * <li>the weights array contains one or more infinite values * <li>the weights array contains one or more NaN values * <li>the weights array contains negative values * </ul>

    * <p> * Uses the formula, <pre> * weighted sum = Σ(values[i] * weights[i]) * </pre>

    * * @param values the input array * @param weights the weights array * @return the sum of the values or Double.NaN if length = 0 * @throws IllegalArgumentException if the parameters are not valid * @since 2.1 */ public double evaluate(final double[] values, final double[] weights) { return evaluate(values, weights, 0, values.length); } /** * {@inheritDoc} */ @Override public Sum copy() { Sum result = new Sum(); copy(this, result); return result; } /** * Copies source to dest. * <p>Neither source nor dest can be null.

    * * @param source Sum to copy * @param dest Sum to copy to * @throws NullPointerException if either source or dest is null */ public static void copy(Sum source, Sum dest) { dest.n = source.n; dest.value = source.value; } }

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