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Java example source code file (UnivariatePeriodicInterpolatorTest.java)

This example Java source code file (UnivariatePeriodicInterpolatorTest.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

linearinterpolator, random, test, univariatefunction, univariateinterpolator, univariateperiodicinterpolator, univariateperiodicinterpolatortest, util

The UnivariatePeriodicInterpolatorTest.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,
 * 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.interpolation;

import java.util.Random;
import org.apache.commons.math3.analysis.UnivariateFunction;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.exception.NumberIsTooSmallException;
import org.apache.commons.math3.exception.NonMonotonicSequenceException;

import org.junit.Assert;
import org.junit.Test;


/**
 * Test for {@link UnivariatePeriodicInterpolator}.
 */
public class UnivariatePeriodicInterpolatorTest {
    private final Random rng = new Random(1224465L);

    @Test
    public void testSine() {
        final int n = 30;
        final double[] xval = new double[n];
        final double[] yval = new double[n];
        final double period = 12.3;
        final double offset = 45.67;

        double delta = 0;
        for (int i = 0; i < n; i++) {
            delta += rng.nextDouble() * period / n;
            xval[i] = offset + delta;
            yval[i] = FastMath.sin(xval[i]);
        }

        final UnivariateInterpolator inter = new LinearInterpolator();
        final UnivariateFunction f = inter.interpolate(xval, yval);

        final UnivariateInterpolator interP
            = new UnivariatePeriodicInterpolator(new LinearInterpolator(),
                                                     period, 1);
        final UnivariateFunction fP = interP.interpolate(xval, yval);

        // Comparing with original interpolation algorithm.
        final double xMin = xval[0];
        final double xMax = xval[n - 1];
        for (int i = 0; i < n; i++) {
            final double x = xMin + (xMax - xMin) * rng.nextDouble();
            final double y = f.value(x);
            final double yP = fP.value(x);

            Assert.assertEquals("x=" + x, y, yP, Math.ulp(1d));
        }

        // Test interpolation outside the primary interval.
        for (int i = 0; i < n; i++) {
            final double xIn = offset + rng.nextDouble() * period;
            final double xOut = xIn + rng.nextInt(123456789) * period;
            final double yIn = fP.value(xIn);
            final double yOut = fP.value(xOut);

            Assert.assertEquals(yIn, yOut, 1e-7);
        }
    }

    @Test
    public void testLessThanOnePeriodCoverage() {
        final int n = 30;
        final double[] xval = new double[n];
        final double[] yval = new double[n];
        final double period = 12.3;
        final double offset = 45.67;

        double delta = period / 2;
        for (int i = 0; i < n; i++) {
            delta += period / (2 * n) * rng.nextDouble();
            xval[i] = offset + delta;
            yval[i] = FastMath.sin(xval[i]);
        }

        final UnivariateInterpolator interP
            = new UnivariatePeriodicInterpolator(new LinearInterpolator(),
                                                     period, 1);
        final UnivariateFunction fP = interP.interpolate(xval, yval);

        // Test interpolation outside the sample data interval.
        for (int i = 0; i < n; i++) {
            final double xIn = offset + rng.nextDouble() * period;
            final double xOut = xIn + rng.nextInt(123456789) * period;
            final double yIn = fP.value(xIn);
            final double yOut = fP.value(xOut);

            Assert.assertEquals(yIn, yOut, 1e-7);
        }
    }

    @Test
    public void testMoreThanOnePeriodCoverage() {
        final int n = 30;
        final double[] xval = new double[n];
        final double[] yval = new double[n];
        final double period = 12.3;
        final double offset = 45.67;

        double delta = period / 2;
        for (int i = 0; i < n; i++) {
            delta += 10 * period / n * rng.nextDouble();
            xval[i] = offset + delta;
            yval[i] = FastMath.sin(xval[i]);
        }

        final UnivariateInterpolator interP
            = new UnivariatePeriodicInterpolator(new LinearInterpolator(),
                                                     period, 1);
        final UnivariateFunction fP = interP.interpolate(xval, yval);

        // Test interpolation outside the sample data interval.
        for (int i = 0; i < n; i++) {
            final double xIn = offset + rng.nextDouble() * period;
            final double xOut = xIn + rng.nextInt(123456789) * period;
            final double yIn = fP.value(xIn);
            final double yOut = fP.value(xOut);

            Assert.assertEquals(yIn, yOut, 1e-6);
        }
    }

    @Test(expected=NumberIsTooSmallException.class)
    public void testTooFewSamples() {
        final double[] xval = { 2, 3, 7 };
        final double[] yval = { 1, 6, 5 };
        final double period = 10;

        final UnivariateInterpolator interpolator
            = new UnivariatePeriodicInterpolator(new LinearInterpolator(), period);
        interpolator.interpolate(xval, yval);
    }

    @Test(expected=NonMonotonicSequenceException.class)
    public void testUnsortedSamples() {
        final double[] xval = { 2, 3, 7, 4, 6 };
        final double[] yval = { 1, 6, 5, -1, -2 };
        final double period = 10;

        final UnivariateInterpolator interpolator
            = new UnivariatePeriodicInterpolator(new LinearInterpolator(), period);
        interpolator.interpolate(xval, yval);
    }
}

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