001    /* ===========================================================
002     * JFreeChart : a free chart library for the Java(tm) platform
003     * ===========================================================
004     *
005     * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
006     *
007     * Project Info:  http://www.jfree.org/jfreechart/index.html
008     *
009     * This library is free software; you can redistribute it and/or modify it 
010     * under the terms of the GNU Lesser General Public License as published by 
011     * the Free Software Foundation; either version 2.1 of the License, or 
012     * (at your option) any later version.
013     *
014     * This library is distributed in the hope that it will be useful, but 
015     * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
016     * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
017     * License for more details.
018     *
019     * You should have received a copy of the GNU Lesser General Public
020     * License along with this library; if not, write to the Free Software
021     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
022     * USA.  
023     *
024     * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
025     * in the United States and other countries.]
026     *
027     * --------------------
028     * PowerFunction2D.java
029     * --------------------
030     * (C) Copyright 2002-2005, by Object Refinery Limited.
031     *
032     * Original Author:  David Gilbert (for Object Refinery Limited);
033     * Contributor(s):   -;
034     *
035     * $Id: PowerFunction2D.java,v 1.3.2.1 2005/10/25 21:31:32 mungady Exp $
036     *
037     * Changes:
038     * --------
039     * 01-Oct-2002 : Version 1 (DG);
040     *
041     */
042    
043    package org.jfree.data.function;
044    
045    
046    /**
047     * A function of the form y = a * x ^ b.
048     */
049    public class PowerFunction2D implements Function2D {
050    
051        /** The 'a' coefficient. */
052        private double a;
053    
054        /** The 'b' coefficient. */
055        private double b;
056    
057        /**
058         * Creates a new power function.
059         *
060         * @param a  the 'a' coefficient.
061         * @param b  the 'b' coefficient.
062         */
063        public PowerFunction2D(double a, double b) {
064            this.a = a;
065            this.b = b;
066        }
067    
068        /**
069         * Returns the value of the function for a given input ('x').
070         *
071         * @param x  the x-value.
072         *
073         * @return The value.
074         */
075        public double getValue(double x) {
076            return this.a * Math.pow(x, this.b);
077        }
078    
079    }