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Diffstat (limited to 'src/main/java/org/apache/commons/math/stat/descriptive/summary/SumOfSquares.java')
-rw-r--r-- | src/main/java/org/apache/commons/math/stat/descriptive/summary/SumOfSquares.java | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math/stat/descriptive/summary/SumOfSquares.java b/src/main/java/org/apache/commons/math/stat/descriptive/summary/SumOfSquares.java new file mode 100644 index 0000000..a632bf6 --- /dev/null +++ b/src/main/java/org/apache/commons/math/stat/descriptive/summary/SumOfSquares.java @@ -0,0 +1,154 @@ +/* + * 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 squares of the available values. + * <p> + * If there are no values in the dataset, or any of the values are + * <code>NaN</code>, then <code>NaN</code> is returned.</p> + * <p> + * <strong>Note that this implementation is not synchronized.</strong> If + * multiple threads access an instance of this class concurrently, and at least + * one of the threads invokes the <code>increment()</code> or + * <code>clear()</code> method, it must be synchronized externally.</p> + * + * @version $Revision: 1006299 $ $Date: 2010-10-10 16:47:17 +0200 (dim. 10 oct. 2010) $ + */ +public class SumOfSquares extends AbstractStorelessUnivariateStatistic implements Serializable { + + /** Serializable version identifier */ + private static final long serialVersionUID = 1460986908574398008L; + + /** */ + private long n; + + /** + * The currently running sumSq + */ + private double value; + + /** + * Create a SumOfSquares instance + */ + public SumOfSquares() { + n = 0; + value = Double.NaN; + } + + /** + * Copy constructor, creates a new {@code SumOfSquares} identical + * to the {@code original} + * + * @param original the {@code SumOfSquares} instance to copy + */ + public SumOfSquares(SumOfSquares original) { + copy(original, this); + } + + /** + * {@inheritDoc} + */ + @Override + public void increment(final double d) { + if (n == 0) { + value = d * d; + } else { + value += d * 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; + } + + /** + * Returns the sum of the squares of the entries in the specified portion of + * the input array, or <code>Double.NaN</code> if the designated subarray + * is empty. + * <p> + * Throws <code>IllegalArgumentException</code> if the array is null.</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 squares 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 sumSq = Double.NaN; + if (test(values, begin, length)) { + sumSq = 0.0; + for (int i = begin; i < begin + length; i++) { + sumSq += values[i] * values[i]; + } + } + return sumSq; + } + + /** + * {@inheritDoc} + */ + @Override + public SumOfSquares copy() { + SumOfSquares result = new SumOfSquares(); + copy(this, result); + return result; + } + + /** + * Copies source to dest. + * <p>Neither source nor dest can be null.</p> + * + * @param source SumOfSquares to copy + * @param dest SumOfSquares to copy to + * @throws NullPointerException if either source or dest is null + */ + public static void copy(SumOfSquares source, SumOfSquares dest) { + dest.setData(source.getDataRef()); + dest.n = source.n; + dest.value = source.value; + } + +} |