/*
* 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 org.apache.commons.math4.analysis.BivariateFunction;
import org.apache.commons.math4.distribution.RealDistribution;
import org.apache.commons.math4.distribution.UniformRealDistribution;
import org.apache.commons.math4.exception.DimensionMismatchException;
import org.apache.commons.math4.exception.MathIllegalArgumentException;
import org.apache.commons.rng.UniformRandomProvider;
import org.apache.commons.rng.simple.RandomSource;
import org.junit.Assert;
import org.junit.Test;
/**
* Test case for the bicubic interpolator.
*/
public final class BicubicInterpolatorTest {
/**
* Test preconditions.
*/
@Test
public void testPreconditions() {
double[] xval = new double[] {3, 4, 5, 6.5};
double[] yval = new double[] {-4, -3, -1, 2.5};
double[][] zval = new double[xval.length][yval.length];
BivariateGridInterpolator interpolator = new BicubicInterpolator();
@SuppressWarnings("unused")
BivariateFunction p = interpolator.interpolate(xval, yval, zval);
double[] wxval = new double[] {3, 2, 5, 6.5};
try {
p = interpolator.interpolate(wxval, yval, zval);
Assert.fail("an exception should have been thrown");
} catch (MathIllegalArgumentException e) {
// Expected
}
double[] wyval = new double[] {-4, -3, -1, -1};
try {
p = interpolator.interpolate(xval, wyval, zval);
Assert.fail("an exception should have been thrown");
} catch (MathIllegalArgumentException e) {
// Expected
}
double[][] wzval = new double[xval.length][yval.length + 1];
try {
p = interpolator.interpolate(xval, yval, wzval);
Assert.fail("an exception should have been thrown");
} catch (DimensionMismatchException e) {
// Expected
}
wzval = new double[xval.length - 1][yval.length];
try {
p = interpolator.interpolate(xval, yval, wzval);
Assert.fail("an exception should have been thrown");
} catch (DimensionMismatchException e) {
// Expected
}
}
/**
* Interpolating a plane.
* <p>
* z = 2 x - 3 y + 5
*/
@Test
public void testPlane() {
BivariateFunction f = new BivariateFunction() {
@Override
public double value(double x, double y) {
return 2 * x - 3 * y + 5;
}
};
testInterpolation(3000,
1e-13,
f,
false);
}
/**
* Interpolating a paraboloid.
* <p>
* z = 2 x<sup>2</sup> - 3 y<sup>2</sup> + 4 x y - 5
*/
@Test
public void testParaboloid() {
BivariateFunction f = new BivariateFunction() {
@Override
public double value(double x, double y) {
return 2 * x * x - 3 * y * y + 4 * x * y - 5;
}
};
testInterpolation(3000,
1e-12,
f,
false);
}
/**
* @param numSamples Number of test samples.
* @param tolerance Allowed tolerance on the interpolated value.
* @param f Test function.
* @param print Whether to print debugging output to the console.
*/
private void testInterpolation(int numSamples,
double tolerance,
BivariateFunction f,
boolean print) {
final int sz = 21;
final double[] xval = new double[sz];
final double[] yval = new double[sz];
// Coordinate values
final double delta = 1d / (sz - 1);
for (int i = 0; i < sz; i++) {
xval[i] = -1 + 15 * i * delta;
yval[i] = -20 + 30 * i * delta;
}
final double[][] zval = new double[xval.length][yval.length];
for (int i = 0; i < xval.length; i++) {
for (int j = 0; j < yval.length; j++) {
zval[i][j] = f.value(xval[i], yval[j]);
}
}
final BicubicInterpolator interpolator = new BicubicInterpolator();
final BicubicInterpolatingFunction p = interpolator.interpolate(xval, yval, zval);
double x, y;
final UniformRandomProvider rng = RandomSource.create(RandomSource.WELL_19937_C);
final RealDistribution.Sampler distX = new UniformRealDistribution(xval[0], xval[xval.length - 1]).createSampler(rng);
final RealDistribution.Sampler distY = new UniformRealDistribution(yval[0], yval[yval.length - 1]).createSampler(rng);
int count = 0;
while (true) {
x = distX.sample();
y = distY.sample();
if (!p.isValidPoint(x, y)) {
if (print) {
System.out.println("# " + x + " " + y);
}
continue;
}
if (count++ > numSamples) {
break;
}
final double expected = f.value(x, y);
final double actual = p.value(x, y);
if (print) {
System.out.println(x + " " + y + " " + expected + " " + actual);
}
Assert.assertEquals(expected, actual, tolerance);
}
}
}