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Java example source code file (SumOfLogs.java)

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

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractstorelessunivariatestatistic, mathillegalargumentexception, nullargumentexception, override, serializable, sumoflogs

The SumOfLogs.java Java example 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package org.apache.commons.math3.stat.descriptive.summary;

import java.io.Serializable;

import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.exception.NullArgumentException;
import org.apache.commons.math3.stat.descriptive.AbstractStorelessUnivariateStatistic;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.MathUtils;

 * Returns the sum of the natural logs for this collection of values.
 * <p>
 * Uses {@link org.apache.commons.math3.util.FastMath#log(double)} to compute the logs.
 * Therefore,
 * <ul>
 * <li>If any of values are < 0, the result is NaN.
 * <li>If all values are non-negative and less than
 * <code>Double.POSITIVE_INFINITY,  but at least one value is 0, the
 * result is <code>Double.NEGATIVE_INFINITY.
 * <li>If both Double.POSITIVE_INFINITY and
 * <code>Double.NEGATIVE_INFINITY are among the values, the result is
 * <code>NaN.
 * </ul>

* <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.

* */ public class SumOfLogs extends AbstractStorelessUnivariateStatistic implements Serializable { /** Serializable version identifier */ private static final long serialVersionUID = -370076995648386763L; /**Number of values that have been added */ private int n; /** * The currently running value */ private double value; /** * Create a SumOfLogs instance */ public SumOfLogs() { value = 0d; n = 0; } /** * Copy constructor, creates a new {@code SumOfLogs} identical * to the {@code original} * * @param original the {@code SumOfLogs} instance to copy * @throws NullArgumentException if original is null */ public SumOfLogs(SumOfLogs original) throws NullArgumentException { copy(original, this); } /** * {@inheritDoc} */ @Override public void increment(final double d) { value += FastMath.log(d); n++; } /** * {@inheritDoc} */ @Override public double getResult() { return value; } /** * {@inheritDoc} */ public long getN() { return n; } /** * {@inheritDoc} */ @Override public void clear() { value = 0d; n = 0; } /** * Returns the sum of the natural logs of the entries in the specified portion of * the input array, or <code>Double.NaN if the designated subarray * is empty. * <p> * Throws <code>MathIllegalArgumentException if the array is null.

* <p> * See {@link SumOfLogs}.</p> * * @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 natural logs of the values or 0 if * length = 0 * @throws MathIllegalArgumentException 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) throws MathIllegalArgumentException { double sumLog = Double.NaN; if (test(values, begin, length, true)) { sumLog = 0.0; for (int i = begin; i < begin + length; i++) { sumLog += FastMath.log(values[i]); } } return sumLog; } /** * {@inheritDoc} */ @Override public SumOfLogs copy() { SumOfLogs result = new SumOfLogs(); // No try-catch or advertised exception here because args are valid copy(this, result); return result; } /** * Copies source to dest. * <p>Neither source nor dest can be null.

* * @param source SumOfLogs to copy * @param dest SumOfLogs to copy to * @throws NullArgumentException if either source or dest is null */ public static void copy(SumOfLogs source, SumOfLogs dest) throws NullArgumentException { MathUtils.checkNotNull(source); MathUtils.checkNotNull(dest); dest.setData(source.getDataRef()); dest.n = source.n; dest.value = source.value; } }

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