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Diffstat (limited to 'src/main/java/org/apache/commons/math3/stat/descriptive/summary/Product.java')
| -rw-r--r-- | src/main/java/org/apache/commons/math3/stat/descriptive/summary/Product.java | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/stat/descriptive/summary/Product.java b/src/main/java/org/apache/commons/math3/stat/descriptive/summary/Product.java new file mode 100644 index 0000000..7d313a5 --- /dev/null +++ b/src/main/java/org/apache/commons/math3/stat/descriptive/summary/Product.java @@ -0,0 +1,230 @@ +/* + * 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.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.stat.descriptive.WeightedEvaluation; +import org.apache.commons.math3.util.FastMath; +import org.apache.commons.math3.util.MathUtils; + +/** + * Returns the product of the available values. + * <p> + * If there are no values in the dataset, then 1 is returned. + * If 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> + * + */ +public class Product extends AbstractStorelessUnivariateStatistic implements Serializable, WeightedEvaluation { + + /** Serializable version identifier */ + private static final long serialVersionUID = 2824226005990582538L; + + /**The number of values that have been added */ + private long n; + + /** + * The current Running Product. + */ + private double value; + + /** + * Create a Product instance + */ + public Product() { + n = 0; + value = 1; + } + + /** + * Copy constructor, creates a new {@code Product} identical + * to the {@code original} + * + * @param original the {@code Product} instance to copy + * @throws NullArgumentException if original is null + */ + public Product(Product original) throws NullArgumentException { + copy(original, this); + } + + /** + * {@inheritDoc} + */ + @Override + public void increment(final double d) { + value *= d; + n++; + } + + /** + * {@inheritDoc} + */ + @Override + public double getResult() { + return value; + } + + /** + * {@inheritDoc} + */ + public long getN() { + return n; + } + + /** + * {@inheritDoc} + */ + @Override + public void clear() { + value = 1; + n = 0; + } + + /** + * Returns the product 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>MathIllegalArgumentException</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 product of the values or 1 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 product = Double.NaN; + if (test(values, begin, length, true)) { + product = 1.0; + for (int i = begin; i < begin + length; i++) { + product *= values[i]; + } + } + return product; + } + + /** + * <p>Returns the weighted product of the entries in the specified portion of + * the input array, or <code>Double.NaN</code> if the designated subarray + * is empty.</p> + * + * <p>Throws <code>MathIllegalArgumentException</code> if any of the following are true: + * <ul><li>the values array is null</li> + * <li>the weights array is null</li> + * <li>the weights array does not have the same length as the values array</li> + * <li>the weights array contains one or more infinite values</li> + * <li>the weights array contains one or more NaN values</li> + * <li>the weights array contains negative values</li> + * <li>the start and length arguments do not determine a valid array</li> + * </ul></p> + * + * <p>Uses the formula, <pre> + * weighted product = ∏values[i]<sup>weights[i]</sup> + * </pre> + * that is, the weights are applied as exponents when computing the weighted product.</p> + * + * @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 product of the values or 1 if length = 0 + * @throws MathIllegalArgumentException if the parameters are not valid + * @since 2.1 + */ + public double evaluate(final double[] values, final double[] weights, + final int begin, final int length) throws MathIllegalArgumentException { + double product = Double.NaN; + if (test(values, weights, begin, length, true)) { + product = 1.0; + for (int i = begin; i < begin + length; i++) { + product *= FastMath.pow(values[i], weights[i]); + } + } + return product; + } + + /** + * <p>Returns the weighted product of the entries in the input array.</p> + * + * <p>Throws <code>MathIllegalArgumentException</code> if any of the following are true: + * <ul><li>the values array is null</li> + * <li>the weights array is null</li> + * <li>the weights array does not have the same length as the values array</li> + * <li>the weights array contains one or more infinite values</li> + * <li>the weights array contains one or more NaN values</li> + * <li>the weights array contains negative values</li> + * </ul></p> + * + * <p>Uses the formula, <pre> + * weighted product = ∏values[i]<sup>weights[i]</sup> + * </pre> + * that is, the weights are applied as exponents when computing the weighted product.</p> + * + * @param values the input array + * @param weights the weights array + * @return the product of the values or Double.NaN if length = 0 + * @throws MathIllegalArgumentException if the parameters are not valid + * @since 2.1 + */ + public double evaluate(final double[] values, final double[] weights) + throws MathIllegalArgumentException { + return evaluate(values, weights, 0, values.length); + } + + + /** + * {@inheritDoc} + */ + @Override + public Product copy() { + Product result = new Product(); + // No try-catch or advertised exception because args are valid + copy(this, result); + return result; + } + + /** + * Copies source to dest. + * <p>Neither source nor dest can be null.</p> + * + * @param source Product to copy + * @param dest Product to copy to + * @throws NullArgumentException if either source or dest is null + */ + public static void copy(Product source, Product dest) + throws NullArgumentException { + MathUtils.checkNotNull(source); + MathUtils.checkNotNull(dest); + dest.setData(source.getDataRef()); + dest.n = source.n; + dest.value = source.value; + } + +} |