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Java example source code file (HarmonicCurveFitterTest.java)

This example Java source code file (HarmonicCurveFitterTest.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

arraylist, harmoniccurvefitter, harmoniccurvefittertest, harmonicoscillator, list, random, test, util, weightedobservedpoints

The HarmonicCurveFitterTest.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.fitting;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import org.apache.commons.math3.analysis.function.HarmonicOscillator;
import org.apache.commons.math3.exception.MathIllegalStateException;
import org.apache.commons.math3.exception.NumberIsTooSmallException;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.MathUtils;
import org.junit.Assert;
import org.junit.Test;

public class HarmonicCurveFitterTest {
    /**
     * Zero points is not enough observed points.
     */
    @Test(expected=NumberIsTooSmallException.class)
    public void testPreconditions1() {
        HarmonicCurveFitter.create().fit(new WeightedObservedPoints().toList());
    }

    @Test
    public void testNoError() {
        final double a = 0.2;
        final double w = 3.4;
        final double p = 4.1;
        final HarmonicOscillator f = new HarmonicOscillator(a, w, p);

        final WeightedObservedPoints points = new WeightedObservedPoints();
        for (double x = 0.0; x < 1.3; x += 0.01) {
            points.add(1, x, f.value(x));
        }

        final HarmonicCurveFitter fitter = HarmonicCurveFitter.create();
        final double[] fitted = fitter.fit(points.toList());
        Assert.assertEquals(a, fitted[0], 1.0e-13);
        Assert.assertEquals(w, fitted[1], 1.0e-13);
        Assert.assertEquals(p, MathUtils.normalizeAngle(fitted[2], p), 1e-13);

        final HarmonicOscillator ff = new HarmonicOscillator(fitted[0], fitted[1], fitted[2]);
        for (double x = -1.0; x < 1.0; x += 0.01) {
            Assert.assertTrue(FastMath.abs(f.value(x) - ff.value(x)) < 1e-13);
        }
    }

    @Test
    public void test1PercentError() {
        final Random randomizer = new Random(64925784252L);
        final double a = 0.2;
        final double w = 3.4;
        final double p = 4.1;
        final HarmonicOscillator f = new HarmonicOscillator(a, w, p);

        final WeightedObservedPoints points = new WeightedObservedPoints();
        for (double x = 0.0; x < 10.0; x += 0.1) {
            points.add(1, x, f.value(x) + 0.01 * randomizer.nextGaussian());
        }

        final HarmonicCurveFitter fitter = HarmonicCurveFitter.create();
        final double[] fitted = fitter.fit(points.toList());
        Assert.assertEquals(a, fitted[0], 7.6e-4);
        Assert.assertEquals(w, fitted[1], 2.7e-3);
        Assert.assertEquals(p, MathUtils.normalizeAngle(fitted[2], p), 1.3e-2);
    }

    @Test
    public void testTinyVariationsData() {
        final Random randomizer = new Random(64925784252L);

        final WeightedObservedPoints points = new WeightedObservedPoints();
        for (double x = 0.0; x < 10.0; x += 0.1) {
            points.add(1, x, 1e-7 * randomizer.nextGaussian());
        }

        final HarmonicCurveFitter fitter = HarmonicCurveFitter.create();
        fitter.fit(points.toList());

        // This test serves to cover the part of the code of "guessAOmega"
        // when the algorithm using integrals fails.
    }

    @Test
    public void testInitialGuess() {
        final Random randomizer = new Random(45314242L);
        final double a = 0.2;
        final double w = 3.4;
        final double p = 4.1;
        final HarmonicOscillator f = new HarmonicOscillator(a, w, p);

        final WeightedObservedPoints points = new WeightedObservedPoints();
        for (double x = 0.0; x < 10.0; x += 0.1) {
            points.add(1, x, f.value(x) + 0.01 * randomizer.nextGaussian());
        }

        final HarmonicCurveFitter fitter = HarmonicCurveFitter.create()
            .withStartPoint(new double[] { 0.15, 3.6, 4.5 });
        final double[] fitted = fitter.fit(points.toList());
        Assert.assertEquals(a, fitted[0], 1.2e-3);
        Assert.assertEquals(w, fitted[1], 3.3e-3);
        Assert.assertEquals(p, MathUtils.normalizeAngle(fitted[2], p), 1.7e-2);
    }

    @Test
    public void testUnsorted() {
        Random randomizer = new Random(64925784252L);
        final double a = 0.2;
        final double w = 3.4;
        final double p = 4.1;
        final HarmonicOscillator f = new HarmonicOscillator(a, w, p);

        // Build a regularly spaced array of measurements.
        final int size = 100;
        final double[] xTab = new double[size];
        final double[] yTab = new double[size];
        for (int i = 0; i < size; i++) {
            xTab[i] = 0.1 * i;
            yTab[i] = f.value(xTab[i]) + 0.01 * randomizer.nextGaussian();
        }

        // shake it
        for (int i = 0; i < size; i++) {
            int i1 = randomizer.nextInt(size);
            int i2 = randomizer.nextInt(size);
            double xTmp = xTab[i1];
            double yTmp = yTab[i1];
            xTab[i1] = xTab[i2];
            yTab[i1] = yTab[i2];
            xTab[i2] = xTmp;
            yTab[i2] = yTmp;
        }

        // Pass it to the fitter.
        final WeightedObservedPoints points = new WeightedObservedPoints();
        for (int i = 0; i < size; ++i) {
            points.add(1, xTab[i], yTab[i]);
        }

        final HarmonicCurveFitter fitter = HarmonicCurveFitter.create();
        final double[] fitted = fitter.fit(points.toList());
        Assert.assertEquals(a, fitted[0], 7.6e-4);
        Assert.assertEquals(w, fitted[1], 3.5e-3);
        Assert.assertEquals(p, MathUtils.normalizeAngle(fitted[2], p), 1.5e-2);
    }

    @Test(expected=MathIllegalStateException.class)
    public void testMath844() {
        final double[] y = { 0, 1, 2, 3, 2, 1,
                             0, -1, -2, -3, -2, -1,
                             0, 1, 2, 3, 2, 1,
                             0, -1, -2, -3, -2, -1,
                             0, 1, 2, 3, 2, 1, 0 };
        final List<WeightedObservedPoint> points = new ArrayList();
        for (int i = 0; i < y.length; i++) {
            points.add(new WeightedObservedPoint(1, i, y[i]));
        }

        // The guesser fails because the function is far from an harmonic
        // function: It is a triangular periodic function with amplitude 3
        // and period 12, and all sample points are taken at integer abscissae
        // so function values all belong to the integer subset {-3, -2, -1, 0,
        // 1, 2, 3}.
        new HarmonicCurveFitter.ParameterGuesser(points);
    }
}

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