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* 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.math4.analysis.interpolation;
import java.util.Random;
import org.apache.commons.math4.analysis.UnivariateFunction;
import org.apache.commons.math4.analysis.interpolation.LinearInterpolator;
import org.apache.commons.math4.analysis.interpolation.UnivariateInterpolator;
import org.apache.commons.math4.analysis.interpolation.UnivariatePeriodicInterpolator;
import org.apache.commons.math4.exception.NonMonotonicSequenceException;
import org.apache.commons.math4.exception.NumberIsTooSmallException;
import org.apache.commons.math4.util.FastMath;
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);
}
}