001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.math.util;
031
032/**
033 * Utility methods for dealing with quadratic equations.
034 * 
035 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
036 *
037 */
038public class QuadraticEquation {
039        /**
040         * Solve the general quadratic ax^2 + bx + c = 0 
041         * 
042         * @param a a
043         * @param b b
044         * @param c c
045         * @return the solution
046         */
047        public static float[] solveGeneralQuadratic(float a, float b, float c) {
048                float [] result = new float[2];
049
050                float sqrt_discriminant = (float) Math.sqrt((b * b) - (4 * a * c));
051                float r1 = ((-1 * b) + sqrt_discriminant) / (2 * a);
052                float r2 = ((-1 * b) - sqrt_discriminant) / (2 * a);
053
054                if (r1<r2) {
055                        result[0] = r1; result[1] = r2;
056                } else {
057                        result[0] = r2; result[1] = r1;
058                }
059
060                return result;
061        }
062
063        /**
064         * Solve the general quadratic ax^2 + bx + c = 0
065         *  
066         * @param a a 
067         * @param b b
068         * @param c c
069         * @return the solution
070         */
071        public static double[] solveGeneralQuadratic(double a, double b, double c) {
072                double [] result = new double[2];
073
074                double sqrt_discriminant = Math.sqrt((b * b) - (4 * a * c));
075                double r1 = ((-1 * b) + sqrt_discriminant) / (2 * a);
076                double r2 = ((-1 * b) - sqrt_discriminant) / (2 * a);
077
078                if (r1<r2) {
079                        result[0] = r1; result[1] = r2;
080                } else {
081                        result[0] = r2; result[1] = r1;
082                }
083
084                return result;
085        }
086}