| /* |
| * 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.analysis.interpolation; |
| |
| import org.apache.commons.math.exception.DimensionMismatchException; |
| import org.apache.commons.math.exception.util.LocalizedFormats; |
| import org.apache.commons.math.exception.NumberIsTooSmallException; |
| import org.apache.commons.math.analysis.polynomials.PolynomialFunction; |
| import org.apache.commons.math.analysis.polynomials.PolynomialSplineFunction; |
| import org.apache.commons.math.util.MathUtils; |
| |
| /** |
| * Implements a linear function for interpolation of real univariate functions. |
| * @version $Revision$ $Date$ |
| * @since 2.2 |
| */ |
| public class LinearInterpolator implements UnivariateRealInterpolator { |
| /** |
| * Computes a linear interpolating function for the data set. |
| * @param x the arguments for the interpolation points |
| * @param y the values for the interpolation points |
| * @return a function which interpolates the data set |
| * @throws DimensionMismatchException if {@code x} and {@code y} |
| * have different sizes. |
| * @throws org.apache.commons.math.exception.NonMonotonousSequenceException |
| * if {@code x} is not sorted in strict increasing order. |
| * @throws NumberIsTooSmallException if the size of {@code x} is smaller |
| * than 2. |
| */ |
| public PolynomialSplineFunction interpolate(double x[], double y[]) { |
| if (x.length != y.length) { |
| throw new DimensionMismatchException(x.length, y.length); |
| } |
| |
| if (x.length < 2) { |
| throw new NumberIsTooSmallException(LocalizedFormats.NUMBER_OF_POINTS, |
| x.length, 2, true); |
| } |
| |
| // Number of intervals. The number of data points is n + 1. |
| int n = x.length - 1; |
| |
| MathUtils.checkOrder(x); |
| |
| // Slope of the lines between the datapoints. |
| final double m[] = new double[n]; |
| for (int i = 0; i < n; i++) { |
| m[i] = (y[i + 1] - y[i]) / (x[i + 1] - x[i]); |
| } |
| |
| PolynomialFunction polynomials[] = new PolynomialFunction[n]; |
| final double coefficients[] = new double[2]; |
| for (int i = 0; i < n; i++) { |
| coefficients[0] = y[i]; |
| coefficients[1] = m[i]; |
| polynomials[i] = new PolynomialFunction(coefficients); |
| } |
| |
| return new PolynomialSplineFunction(x, polynomials); |
| } |
| } |