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package org.apache.commons.math.optimization.fitting;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import java.util.Random;
import org.apache.commons.math.optimization.OptimizationException;
import org.apache.commons.math.optimization.general.LevenbergMarquardtOptimizer;
import org.apache.commons.math.util.MathUtils;
import org.junit.Test;
public class HarmonicFitterTest {
@Test
public void testNoError() throws OptimizationException {
HarmonicFunction f = new HarmonicFunction(0.2, 3.4, 4.1);
HarmonicFitter fitter =
new HarmonicFitter(new LevenbergMarquardtOptimizer());
for (double x = 0.0; x < 1.3; x += 0.01) {
fitter.addObservedPoint(1.0, x, f.value(x));
}
HarmonicFunction fitted = fitter.fit();
assertEquals(f.getAmplitude(), fitted.getAmplitude(), 1.0e-13);
assertEquals(f.getPulsation(), fitted.getPulsation(), 1.0e-13);
assertEquals(f.getPhase(), MathUtils.normalizeAngle(fitted.getPhase(), f.getPhase()), 1.0e-13);
for (double x = -1.0; x < 1.0; x += 0.01) {
assertTrue(Math.abs(f.value(x) - fitted.value(x)) < 1.0e-13);
}
}
@Test
public void test1PercentError() throws OptimizationException {
Random randomizer = new Random(64925784252l);
HarmonicFunction f = new HarmonicFunction(0.2, 3.4, 4.1);
HarmonicFitter fitter =
new HarmonicFitter(new LevenbergMarquardtOptimizer());
for (double x = 0.0; x < 10.0; x += 0.1) {
fitter.addObservedPoint(1.0, x,
f.value(x) + 0.01 * randomizer.nextGaussian());
}
HarmonicFunction fitted = fitter.fit();
assertEquals(f.getAmplitude(), fitted.getAmplitude(), 7.6e-4);
assertEquals(f.getPulsation(), fitted.getPulsation(), 2.7e-3);
assertEquals(f.getPhase(), MathUtils.normalizeAngle(fitted.getPhase(), f.getPhase()), 1.3e-2);
}
@Test
public void testInitialGuess() throws OptimizationException {
Random randomizer = new Random(45314242l);
HarmonicFunction f = new HarmonicFunction(0.2, 3.4, 4.1);
HarmonicFitter fitter =
new HarmonicFitter(new LevenbergMarquardtOptimizer(), new double[] { 0.15, 3.6, 4.5 });
for (double x = 0.0; x < 10.0; x += 0.1) {
fitter.addObservedPoint(1.0, x,
f.value(x) + 0.01 * randomizer.nextGaussian());
}
HarmonicFunction fitted = fitter.fit();
assertEquals(f.getAmplitude(), fitted.getAmplitude(), 1.2e-3);
assertEquals(f.getPulsation(), fitted.getPulsation(), 3.3e-3);
assertEquals(f.getPhase(), MathUtils.normalizeAngle(fitted.getPhase(), f.getPhase()), 1.7e-2);
}
@Test
public void testUnsorted() throws OptimizationException {
Random randomizer = new Random(64925784252l);
HarmonicFunction f = new HarmonicFunction(0.2, 3.4, 4.1);
HarmonicFitter fitter =
new HarmonicFitter(new LevenbergMarquardtOptimizer());
// build a regularly spaced array of measurements
int size = 100;
double[] xTab = new double[size];
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
for (int i = 0; i < size; ++i) {
fitter.addObservedPoint(1.0, xTab[i], yTab[i]);
}
HarmonicFunction fitted = fitter.fit();
assertEquals(f.getAmplitude(), fitted.getAmplitude(), 7.6e-4);
assertEquals(f.getPulsation(), fitted.getPulsation(), 3.5e-3);
assertEquals(f.getPhase(), MathUtils.normalizeAngle(fitted.getPhase(), f.getPhase()), 1.5e-2);
}
}