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Java example source code file (LinearInterpolator.java)

This example Java source code file (LinearInterpolator.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

dimensionmismatchexception, linearinterpolator, nonmonotonicsequenceexception, numberistoosmallexception, polynomialfunction, polynomialsplinefunction, univariateinterpolator

The LinearInterpolator.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/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,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package org.apache.commons.math3.analysis.interpolation;

import org.apache.commons.math3.analysis.polynomials.PolynomialFunction;
import org.apache.commons.math3.analysis.polynomials.PolynomialSplineFunction;
import org.apache.commons.math3.util.MathArrays;
import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.NumberIsTooSmallException;
import org.apache.commons.math3.exception.NonMonotonicSequenceException;
import org.apache.commons.math3.exception.util.LocalizedFormats;

 * Implements a linear function for interpolation of real univariate functions.
public class LinearInterpolator implements UnivariateInterpolator {
     * 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 NonMonotonicSequenceException 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[])
        throws DimensionMismatchException,
               NonMonotonicSequenceException {
        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;


        // 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]);

        final 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);

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