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Java example source code file (JacobianFunctionTest.java)

This example Java source code file (JacobianFunctionTest.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

derivativestructure, jacobianfunction, jacobianfunctiontest, multivariatedifferentiablevectorfunction, spheremapping

The JacobianFunctionTest.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.differentiation;

import org.junit.Assert;

import org.apache.commons.math3.TestUtils;
import org.apache.commons.math3.util.FastMath;
import org.junit.Test;


/**
 * Test for class {@link JacobianFunction}.
 */
public class JacobianFunctionTest {

    @Test
    public void testSphere() {
        SphereMapping    f = new SphereMapping(10.0);
        JacobianFunction j = new JacobianFunction(f);
        for (double latitude = -1.5; latitude < 1.5; latitude += 0.1) {
            for (double longitude = -3.1; longitude < 3.1; longitude += 0.1) {
                double[] point = new double[] { latitude, longitude };
                double[][] referenceJacobian  = f.jacobian(point);
                double[][] testJacobian       = j.value(point);
                Assert.assertEquals(referenceJacobian.length, testJacobian.length);
                for (int i = 0; i < 3; ++i) {
                    TestUtils.assertEquals(referenceJacobian[i], testJacobian[i], 2.0e-15);
                }
            }
        }
    }

    /* Maps (latitude, longitude) to (x, y, z) */
    private static class SphereMapping implements MultivariateDifferentiableVectorFunction {

        private final double radius;

        public SphereMapping(final double radius) {
            this.radius = radius;
        }

        public double[] value(double[] point) {
            final double cLat = FastMath.cos(point[0]);
            final double sLat = FastMath.sin(point[0]);
            final double cLon = FastMath.cos(point[1]);
            final double sLon = FastMath.sin(point[1]);
            return new double[] {
                radius * cLon * cLat,
                radius * sLon * cLat,
                radius * sLat
            };
        }

        public DerivativeStructure[] value(DerivativeStructure[] point) {
            final DerivativeStructure cLat = point[0].cos();
            final DerivativeStructure sLat = point[0].sin();
            final DerivativeStructure cLon = point[1].cos();
            final DerivativeStructure sLon = point[1].sin();
            return new DerivativeStructure[] {
                cLon.multiply(cLat).multiply(radius),
                sLon.multiply(cLat).multiply(radius),
                sLat.multiply(radius)
            };
        }

        public double[][] jacobian(double[] point) {
            final double cLat = FastMath.cos(point[0]);
            final double sLat = FastMath.sin(point[0]);
            final double cLon = FastMath.cos(point[1]);
            final double sLon = FastMath.sin(point[1]);
            return new double[][] {
                { -radius * cLon * sLat, -radius * sLon * cLat },
                { -radius * sLon * sLat,  radius * cLon * cLat },
                {  radius * cLat,         0  }
            };
        }

    }

}

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