

Java example source code file (GaussIntegrator.java)
The GaussIntegrator.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/LICENSE2.0 * * 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.analysis.integration.gauss; import org.apache.commons.math3.analysis.UnivariateFunction; import org.apache.commons.math3.exception.DimensionMismatchException; import org.apache.commons.math3.exception.NonMonotonicSequenceException; import org.apache.commons.math3.util.MathArrays; import org.apache.commons.math3.util.Pair; /** * Class that implements the Gaussian rule for * {@link #integrate(UnivariateFunction) integrating} a weighted * function. * * @since 3.1 */ public class GaussIntegrator { /** Nodes. */ private final double[] points; /** Nodes weights. */ private final double[] weights; /** * Creates an integrator from the given {@code points} and {@code weights}. * The integration interval is defined by the first and last value of * {@code points} which must be sorted in increasing order. * * @param points Integration points. * @param weights Weights of the corresponding integration nodes. * @throws NonMonotonicSequenceException if the {@code points} are not * sorted in increasing order. * @throws DimensionMismatchException if points and weights don't have the same length */ public GaussIntegrator(double[] points, double[] weights) throws NonMonotonicSequenceException, DimensionMismatchException { if (points.length != weights.length) { throw new DimensionMismatchException(points.length, weights.length); } MathArrays.checkOrder(points, MathArrays.OrderDirection.INCREASING, true, true); this.points = points.clone(); this.weights = weights.clone(); } /** * Creates an integrator from the given pair of points (first element of * the pair) and weights (second element of the pair. * * @param pointsAndWeights Integration points and corresponding weights. * @throws NonMonotonicSequenceException if the {@code points} are not * sorted in increasing order. * * @see #GaussIntegrator(double[], double[]) */ public GaussIntegrator(Pair<double[], double[]> pointsAndWeights) throws NonMonotonicSequenceException { this(pointsAndWeights.getFirst(), pointsAndWeights.getSecond()); } /** * Returns an estimate of the integral of {@code f(x) * w(x)}, * where {@code w} is a weight function that depends on the actual * flavor of the Gauss integration scheme. * The algorithm uses the points and associated weights, as passed * to the {@link #GaussIntegrator(double[],double[]) constructor}. * * @param f Function to integrate. * @return the integral of the weighted function. */ public double integrate(UnivariateFunction f) { double s = 0; double c = 0; for (int i = 0; i < points.length; i++) { final double x = points[i]; final double w = weights[i]; final double y = w * f.value(x)  c; final double t = s + y; c = (t  s)  y; s = t; } return s; } /** * @return the order of the integration rule (the number of integration * points). */ public int getNumberOfPoints() { return points.length; } /** * Gets the integration point at the given index. * The index must be in the valid range but no check is performed. * @param index index of the integration point * @return the integration point. */ public double getPoint(int index) { return points[index]; } /** * Gets the weight of the integration point at the given index. * The index must be in the valid range but no check is performed. * @param index index of the integration point * @return the weight. */ public double getWeight(int index) { return weights[index]; } } Other Java examples (source code examples)Here is a short list of links related to this Java GaussIntegrator.java source code file: 
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