001 /* =========================================================== 002 * JFreeChart : a free chart library for the Java(tm) platform 003 * =========================================================== 004 * 005 * (C) Copyright 2000-2007, 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 * LogFormat.java 029 * -------------- 030 * (C) Copyright 2007, by Object Refinery Limited and Contributors. 031 * 032 * Original Author: David Gilbert (for Object Refinery Limited); 033 * Contributor(s): -; 034 * 035 * Changes 036 * ------- 037 * 02-Aug-2007 : Version 1 (DG); 038 * 039 */ 040 041 package org.jfree.chart.util; 042 043 import java.text.DecimalFormat; 044 import java.text.FieldPosition; 045 import java.text.NumberFormat; 046 import java.text.ParsePosition; 047 048 /** 049 * A number formatter for logarithmic values. This formatter does not support 050 * parsing. 051 * 052 * @since 1.0.7 053 */ 054 public class LogFormat extends NumberFormat { 055 056 /** The log base value. */ 057 private double base; 058 059 /** The natural logarithm of the base value. */ 060 private double baseLog; 061 062 /** The label for the log base (for example, "e"). */ 063 private String baseLabel; 064 065 /** A flag that controls whether or not the base is shown. */ 066 private boolean showBase; 067 068 /** The number formatter for the exponent. */ 069 private NumberFormat formatter = new DecimalFormat("0.0"); 070 071 /** 072 * Creates a new instance. 073 * 074 * @param base the base. 075 * @param baseLabel the base label. 076 * @param showBase a flag that controls whether or not the base value is 077 * shown. 078 */ 079 public LogFormat(double base, String baseLabel, boolean showBase) { 080 this.base = base; 081 this.baseLog = Math.log(this.base); 082 this.baseLabel = baseLabel; 083 this.showBase = showBase; 084 } 085 086 /** 087 * Calculates the log of a given value. 088 * 089 * @param value the value. 090 * 091 * @return The log of the value. 092 */ 093 private double calculateLog(double value) { 094 return Math.log(value) / this.baseLog; 095 } 096 097 /** 098 * Returns a formatted representation of the specified number. 099 * 100 * @param number the number. 101 * @param toAppendTo the string buffer to append to. 102 * @param pos the position. 103 * 104 * @return A string buffer containing the formatted value. 105 */ 106 public StringBuffer format(double number, StringBuffer toAppendTo, 107 FieldPosition pos) { 108 StringBuffer result = new StringBuffer(); 109 if (this.showBase) { 110 result.append(this.baseLabel); 111 result.append("^"); 112 } 113 result.append(this.formatter.format(calculateLog(number))); 114 return result; 115 } 116 117 /** 118 * Formats the specified number as a hexadecimal string. The decimal 119 * fraction is ignored. 120 * 121 * @param number the number to format. 122 * @param toAppendTo the buffer to append to (ignored here). 123 * @param pos the field position (ignored here). 124 * 125 * @return The string buffer. 126 */ 127 public StringBuffer format(long number, StringBuffer toAppendTo, 128 FieldPosition pos) { 129 StringBuffer result = new StringBuffer(); 130 if (this.showBase) { 131 result.append(this.baseLabel); 132 result.append("^"); 133 } 134 result.append(this.formatter.format(calculateLog(number))); 135 return result; 136 } 137 138 /** 139 * Parsing is not implemented, so this method always returns 140 * <code>null</code>. 141 * 142 * @param source ignored. 143 * @param parsePosition ignored. 144 * 145 * @return Always <code>null</code>. 146 */ 147 public Number parse (String source, ParsePosition parsePosition) { 148 return null; // don't bother with parsing 149 } 150 151 }