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Java example source code file (BicubicInterpolatorTest.java)

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

Learn more about this Java project at its project page.

Java - Java tags/keywords

bicubicinterpolatingfunction, bicubicinterpolator, bicubicinterpolatortest, bivariatefunction, bivariategridinterpolator, dimensionmismatchexception, mathillegalargumentexception, randomgenerator, suppresswarnings, test, uniformrealdistribution, well19937c

The BicubicInterpolatorTest.java Java example 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.math3.analysis.interpolation;

import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.analysis.BivariateFunction;
import org.apache.commons.math3.distribution.UniformRealDistribution;
import org.apache.commons.math3.random.RandomGenerator;
import org.apache.commons.math3.random.Well19937c;
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() {
                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 - 3 y2 + 4 x y - 5
     */
    @Test
    public void testParaboloid() {
        BivariateFunction f = new BivariateFunction() {
                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 RandomGenerator rng = new Well19937c();
        final UniformRealDistribution distX = new UniformRealDistribution(rng, xval[0], xval[xval.length - 1]);
        final UniformRealDistribution distY = new UniformRealDistribution(rng, yval[0], yval[yval.length - 1]);

        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);
        }
    }
}

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