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Commons Math example source code file (PolynomialFunctionLagrangeFormTest.java)

This example Commons Math source code file (PolynomialFunctionLagrangeFormTest.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

exception, expecting, expecting, illegalargumentexception, illegalargumentexception, mathexception, mathexception, polynomialfunctionlagrangeform, polynomialfunctionlagrangeform, polynomialfunctionlagrangeformtest, testcase

The Commons Math PolynomialFunctionLagrangeFormTest.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.polynomials;

import org.apache.commons.math.MathException;
import junit.framework.TestCase;

/**
 * Testcase for Lagrange form of polynomial function.
 * <p>
 * We use n+1 points to interpolate a polynomial of degree n. This should
 * give us the exact same polynomial as result. Thus we can use a very
 * small tolerance to account only for round-off errors.
 *
 * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $
 */
public final class PolynomialFunctionLagrangeFormTest extends TestCase {

    /**
     * Test of polynomial for the linear function.
     */
    public void testLinearFunction() throws MathException {
        PolynomialFunctionLagrangeForm p;
        double c[], z, expected, result, tolerance = 1E-12;

        // p(x) = 1.5x - 4
        double x[] = { 0.0, 3.0 };
        double y[] = { -4.0, 0.5 };
        p = new PolynomialFunctionLagrangeForm(x, y);

        z = 2.0; expected = -1.0; result = p.value(z);
        assertEquals(expected, result, tolerance);

        z = 4.5; expected = 2.75; result = p.value(z);
        assertEquals(expected, result, tolerance);

        z = 6.0; expected = 5.0; result = p.value(z);
        assertEquals(expected, result, tolerance);

        assertEquals(1, p.degree());

        c = p.getCoefficients();
        assertEquals(2, c.length);
        assertEquals(-4.0, c[0], tolerance);
        assertEquals(1.5, c[1], tolerance);
    }

    /**
     * Test of polynomial for the quadratic function.
     */
    public void testQuadraticFunction() throws MathException {
        PolynomialFunctionLagrangeForm p;
        double c[], z, expected, result, tolerance = 1E-12;

        // p(x) = 2x^2 + 5x - 3 = (2x - 1)(x + 3)
        double x[] = { 0.0, -1.0, 0.5 };
        double y[] = { -3.0, -6.0, 0.0 };
        p = new PolynomialFunctionLagrangeForm(x, y);

        z = 1.0; expected = 4.0; result = p.value(z);
        assertEquals(expected, result, tolerance);

        z = 2.5; expected = 22.0; result = p.value(z);
        assertEquals(expected, result, tolerance);

        z = -2.0; expected = -5.0; result = p.value(z);
        assertEquals(expected, result, tolerance);

        assertEquals(2, p.degree());

        c = p.getCoefficients();
        assertEquals(3, c.length);
        assertEquals(-3.0, c[0], tolerance);
        assertEquals(5.0, c[1], tolerance);
        assertEquals(2.0, c[2], tolerance);
    }

    /**
     * Test of polynomial for the quintic function.
     */
    public void testQuinticFunction() throws MathException {
        PolynomialFunctionLagrangeForm p;
        double c[], z, expected, result, tolerance = 1E-12;

        // p(x) = x^5 - x^4 - 7x^3 + x^2 + 6x = x(x^2 - 1)(x + 2)(x - 3)
        double x[] = { 1.0, -1.0, 2.0, 3.0, -3.0, 0.5 };
        double y[] = { 0.0, 0.0, -24.0, 0.0, -144.0, 2.34375 };
        p = new PolynomialFunctionLagrangeForm(x, y);

        z = 0.0; expected = 0.0; result = p.value(z);
        assertEquals(expected, result, tolerance);

        z = -2.0; expected = 0.0; result = p.value(z);
        assertEquals(expected, result, tolerance);

        z = 4.0; expected = 360.0; result = p.value(z);
        assertEquals(expected, result, tolerance);

        assertEquals(5, p.degree());

        c = p.getCoefficients();
        assertEquals(6, c.length);
        assertEquals(0.0, c[0], tolerance);
        assertEquals(6.0, c[1], tolerance);
        assertEquals(1.0, c[2], tolerance);
        assertEquals(-7.0, c[3], tolerance);
        assertEquals(-1.0, c[4], tolerance);
        assertEquals(1.0, c[5], tolerance);
    }

    /**
     * Test of parameters for the polynomial.
     */
    public void testParameters() throws Exception {

        try {
            // bad input array length
            double x[] = { 1.0 };
            double y[] = { 2.0 };
            new PolynomialFunctionLagrangeForm(x, y);
            fail("Expecting IllegalArgumentException - bad input array length");
        } catch (IllegalArgumentException ex) {
            // expected
        }
        try {
            // mismatch input arrays
            double x[] = { 1.0, 2.0, 3.0, 4.0 };
            double y[] = { 0.0, -4.0, -24.0 };
            new PolynomialFunctionLagrangeForm(x, y);
            fail("Expecting IllegalArgumentException - mismatch input arrays");
        } catch (IllegalArgumentException ex) {
            // expected
        }
    }
}

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