/*
* 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.math.analysis.interpolation;
import org.apache.commons.math.MathException;
import org.apache.commons.math.DimensionMismatchException;
import org.apache.commons.math.analysis.BivariateRealFunction;
import org.junit.Assert;
import org.junit.Test;
/**
* Testcase for the bicubic interpolator.
*
* @version $Revision: 821626 $ $Date: 2009-10-04 23:57:30 +0200 (Sun, 04 Oct 2009) $
*/
public final class SmoothingBicubicSplineInterpolatorTest {
/**
* Test preconditions.
*/
@Test
public void testPreconditions() throws MathException {
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];
BivariateRealGridInterpolator interpolator = new SmoothingBicubicSplineInterpolator();
@SuppressWarnings("unused")
BivariateRealFunction 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 (IllegalArgumentException 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 (IllegalArgumentException e) {
// Expected
}
double[][] wzval = new double[xval.length][yval.length + 1];
try {
p = interpolator.interpolate(xval, wyval, wzval);
Assert.fail("an exception should have been thrown");
} catch (IllegalArgumentException 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
}
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
}
}
/**
* Test of interpolator for a plane.
* <p>
* z = 2 x - 3 y + 5
*/
@Test
public void testPlane() throws MathException {
BivariateRealFunction f = new BivariateRealFunction() {
public double value(double x, double y) {
return 2 * x - 3 * y + 5;
}
};
BivariateRealGridInterpolator interpolator = new SmoothingBicubicSplineInterpolator();
double[] xval = new double[] {3, 4, 5, 6.5};
double[] yval = new double[] {-4, -3, -1, 2, 2.5};
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]);
}
}
BivariateRealFunction p = interpolator.interpolate(xval, yval, zval);
double x, y;
double expected, result;
x = 4;
y = -3;
expected = f.value(x, y);
result = p.value(x, y);
Assert.assertEquals("On sample point", expected, result, 1e-15);
x = 4.5;
y = -1.5;
expected = f.value(x, y);
result = p.value(x, y);
Assert.assertEquals("half-way between sample points (middle of the patch)", expected, result, 0.3);
x = 3.5;
y = -3.5;
expected = f.value(x, y);
result = p.value(x, y);
Assert.assertEquals("half-way between sample points (border of the patch)", expected, result, 0.3);
}
/**
* Test of interpolator for a paraboloid.
* <p>
* z = 2 x<sup>2</sup> - 3 y<sup>2</sup> + 4 x y - 5
*/
@Test
public void testParaboloid() throws MathException {
BivariateRealFunction f = new BivariateRealFunction() {
public double value(double x, double y) {
return 2 * x * x - 3 * y * y + 4 * x * y - 5;
}
};
BivariateRealGridInterpolator interpolator = new SmoothingBicubicSplineInterpolator();
double[] xval = new double[] {3, 4, 5, 6.5};
double[] yval = new double[] {-4, -3, -2, -1, 0.5, 2.5};
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]);
}
}
BivariateRealFunction p = interpolator.interpolate(xval, yval, zval);
double x, y;
double expected, result;
x = 5;
y = 0.5;
expected = f.value(x, y);
result = p.value(x, y);
Assert.assertEquals("On sample point", expected, result, 1e-13);
x = 4.5;
y = -1.5;
expected = f.value(x, y);
result = p.value(x, y);
Assert.assertEquals("half-way between sample points (middle of the patch)", expected, result, 0.2);
x = 3.5;
y = -3.5;
expected = f.value(x, y);
result = p.value(x, y);
Assert.assertEquals("half-way between sample points (border of the patch)", expected, result, 0.2);
}
}