Commons Math example source code file (SmoothingBicubicSplineInterpolatorTest.java)

This example Commons Math source code file (SmoothingBicubicSplineInterpolatorTest.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Math tags/keywords

bivariaterealfunction, bivariaterealfunction, bivariaterealgridinterpolator, bivariaterealgridinterpolator, dimensionmismatchexception, illegalargumentexception, mathexception, on, smoothingbicubicsplineinterpolator, smoothingbicubicsplineinterpolator, smoothingbicubicsplineinterpolatortest, suppresswarnings, test, test

The Commons Math SmoothingBicubicSplineInterpolatorTest.java source code

/*
 * 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 - 3 y2 + 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);
    }
}