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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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package org.apache.commons.math.stat.descriptive.summary;
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import java.io.Serializable;
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import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
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* Returns the sum of the squares of the available values.
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* If there are no values in the dataset, or any of the values are
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* <code>NaN</code>, then <code>NaN</code> is returned.</p>
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* <strong>Note that this implementation is not synchronized.</strong> If
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* multiple threads access an instance of this class concurrently, and at least
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* one of the threads invokes the <code>increment()</code> or
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* <code>clear()</code> method, it must be synchronized externally.</p>
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* @version $Revision: 762087 $ $Date: 2009-04-05 10:20:18 -0400 (Sun, 05 Apr 2009) $
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public class SumOfSquares extends AbstractStorelessUnivariateStatistic implements Serializable {
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/** Serializable version identifier */
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private static final long serialVersionUID = 1460986908574398008L;
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* The currently running sumSq
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* Create a SumOfSquares instance
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public SumOfSquares() {
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* Copy constructor, creates a new {@code SumOfSquares} identical
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* to the {@code original}
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* @param original the {@code SumOfSquares} instance to copy
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public SumOfSquares(SumOfSquares original) {
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public void increment(final double d) {
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public double getResult() {
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* Returns the sum of the squares of the entries in the specified portion of
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* the input array, or <code>Double.NaN</code> if the designated subarray
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* Throws <code>IllegalArgumentException</code> if the array is null.</p>
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* @param values the input array
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* @param begin index of the first array element to include
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* @param length the number of elements to include
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* @return the sum of the squares of the values or Double.NaN if length = 0
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* @throws IllegalArgumentException if the array is null or the array index
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* parameters are not valid
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public double evaluate(final double[] values,final int begin, final int length) {
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double sumSq = Double.NaN;
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if (test(values, begin, length)) {
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for (int i = begin; i < begin + length; i++) {
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sumSq += values[i] * values[i];
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public SumOfSquares copy() {
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SumOfSquares result = new SumOfSquares();
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* Copies source to dest.
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* <p>Neither source nor dest can be null.</p>
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* @param source SumOfSquares to copy
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* @param dest SumOfSquares to copy to
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* @throws NullPointerException if either source or dest is null
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public static void copy(SumOfSquares source, SumOfSquares dest) {
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dest.value = source.value;