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* 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.
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package org.apache.commons.math4.fitting;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import org.apache.commons.math4.analysis.function.HarmonicOscillator;
import org.apache.commons.math4.exception.MathIllegalStateException;
import org.apache.commons.math4.exception.NumberIsTooSmallException;
import org.apache.commons.math4.fitting.HarmonicCurveFitter;
import org.apache.commons.math4.fitting.WeightedObservedPoint;
import org.apache.commons.math4.fitting.WeightedObservedPoints;
import org.apache.commons.math4.util.FastMath;
import org.apache.commons.math4.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);
}
}