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     * StandardTickUnitSource.java
029     * ---------------------------
030     * (C) Copyright 2003, 2004, by Object Refinery Limited.
031     *
032     * Original Author:  David Gilbert (for Object Refinery Limited);
033     * Contributor(s):   -;
034     *
035     * $Id: StandardTickUnitSource.java,v 1.2.2.2 2006/01/27 13:53:28 mungady Exp $
036     *
037     * Changes
038     * -------
039     * 23-Sep-2003 : Version 1 (DG);
040     *
041     */
042    
043    package org.jfree.chart.axis;
044    
045    import java.text.DecimalFormat;
046    
047    /**
048     * A source that can used by the {@link NumberAxis} class to obtain a
049     * suitable {@link TickUnit}.
050     */
051    public class StandardTickUnitSource implements TickUnitSource {
052    
053        /** Constant for log(10.0). */
054        private static final double LOG_10_VALUE = Math.log(10.0);
055        
056        /**
057         * Returns a tick unit that is larger than the supplied unit.
058         *
059         * @param unit  the unit (<code>null</code> not permitted).
060         *
061         * @return A tick unit that is larger than the supplied unit.
062         */
063        public TickUnit getLargerTickUnit(TickUnit unit) {
064            double x = unit.getSize();
065            double log = Math.log(x) / LOG_10_VALUE;
066            double higher = Math.ceil(log);
067            return new NumberTickUnit(Math.pow(10, higher), 
068                    new DecimalFormat("0.0E0"));
069        }
070    
071        /**
072         * Returns the tick unit in the collection that is greater than or equal
073         * to (in size) the specified unit.
074         *
075         * @param unit  the unit (<code>null</code> not permitted).
076         *
077         * @return A unit from the collection.
078         */
079        public TickUnit getCeilingTickUnit(TickUnit unit) {
080            return getLargerTickUnit(unit);
081        }
082    
083        /**
084         * Returns the tick unit in the collection that is greater than or equal
085         * to the specified size.
086         *
087         * @param size  the size.
088         *
089         * @return A unit from the collection.
090         */
091        public TickUnit getCeilingTickUnit(double size) {
092            double log = Math.log(size) / LOG_10_VALUE;
093            double higher = Math.ceil(log);
094            return new NumberTickUnit(Math.pow(10, higher), 
095                    new DecimalFormat("0.0E0"));
096        }
097        
098    }