001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2008, 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 * BoxAndWhiskerCalculator.java
029 * ----------------------------
030 * (C) Copyright 2003-2008,  by Object Refinery Limited and Contributors.
031 *
032 * Original Author:  David Gilbert (for Object Refinery Limited);
033 * Contributor(s):   -;
034 *
035 * Changes
036 * -------
037 * 28-Aug-2003 : Version 1 (DG);
038 * 17-Nov-2003 : Fixed bug in calculations of outliers and median (DG);
039 * 10-Jan-2005 : Removed deprecated methods in preparation for 1.0.0
040 *               release (DG);
041 * ------------- JFREECHART 1.0.x ---------------------------------------------
042 * 15-Nov-2006 : Cleaned up handling of null arguments, and null or NaN items
043 *               in the list (DG);
044 *
045 */
046
047package org.jfree.data.statistics;
048
049import java.util.ArrayList;
050import java.util.Collections;
051import java.util.Iterator;
052import java.util.List;
053
054/**
055 * A utility class that calculates the mean, median, quartiles Q1 and Q3, plus
056 * a list of outlier values...all from an arbitrary list of
057 * <code>Number</code> objects.
058 */
059public abstract class BoxAndWhiskerCalculator {
060
061    /**
062     * Calculates the statistics required for a {@link BoxAndWhiskerItem}
063     * from a list of <code>Number</code> objects.  Any items in the list
064     * that are <code>null</code>, not an instance of <code>Number</code>, or
065     * equivalent to <code>Double.NaN</code>, will be ignored.
066     *
067     * @param values  a list of numbers (a <code>null</code> list is not
068     *                permitted).
069     *
070     * @return A box-and-whisker item.
071     */
072    public static BoxAndWhiskerItem calculateBoxAndWhiskerStatistics(
073                                        List values) {
074        return calculateBoxAndWhiskerStatistics(values, true);
075    }
076
077    /**
078     * Calculates the statistics required for a {@link BoxAndWhiskerItem}
079     * from a list of <code>Number</code> objects.  Any items in the list
080     * that are <code>null</code>, not an instance of <code>Number</code>, or
081     * equivalent to <code>Double.NaN</code>, will be ignored.
082     *
083     * @param values  a list of numbers (a <code>null</code> list is not
084     *                permitted).
085     * @param stripNullAndNaNItems  a flag that controls the handling of null
086     *     and NaN items.
087     *
088     * @return A box-and-whisker item.
089     *
090     * @since 1.0.3
091     */
092    public static BoxAndWhiskerItem calculateBoxAndWhiskerStatistics(
093            List values, boolean stripNullAndNaNItems) {
094
095        if (values == null) {
096            throw new IllegalArgumentException("Null 'values' argument.");
097        }
098
099        List vlist;
100        if (stripNullAndNaNItems) {
101            vlist = new ArrayList(values.size());
102            Iterator iterator = values.listIterator();
103            while (iterator.hasNext()) {
104                Object obj = iterator.next();
105                if (obj instanceof Number) {
106                    Number n = (Number) obj;
107                    double v = n.doubleValue();
108                    if (!Double.isNaN(v)) {
109                        vlist.add(n);
110                    }
111                }
112            }
113        }
114        else {
115            vlist = values;
116        }
117        Collections.sort(vlist);
118
119        double mean = Statistics.calculateMean(vlist, false);
120        double median = Statistics.calculateMedian(vlist, false);
121        double q1 = calculateQ1(vlist);
122        double q3 = calculateQ3(vlist);
123
124        double interQuartileRange = q3 - q1;
125
126        double upperOutlierThreshold = q3 + (interQuartileRange * 1.5);
127        double lowerOutlierThreshold = q1 - (interQuartileRange * 1.5);
128
129        double upperFaroutThreshold = q3 + (interQuartileRange * 2.0);
130        double lowerFaroutThreshold = q1 - (interQuartileRange * 2.0);
131
132        double minRegularValue = Double.POSITIVE_INFINITY;
133        double maxRegularValue = Double.NEGATIVE_INFINITY;
134        double minOutlier = Double.POSITIVE_INFINITY;
135        double maxOutlier = Double.NEGATIVE_INFINITY;
136        List outliers = new ArrayList();
137
138        Iterator iterator = vlist.iterator();
139        while (iterator.hasNext()) {
140            Number number = (Number) iterator.next();
141            double value = number.doubleValue();
142            if (value > upperOutlierThreshold) {
143                outliers.add(number);
144                if (value > maxOutlier && value <= upperFaroutThreshold) {
145                    maxOutlier = value;
146                }
147            }
148            else if (value < lowerOutlierThreshold) {
149                outliers.add(number);
150                if (value < minOutlier && value >= lowerFaroutThreshold) {
151                    minOutlier = value;
152                }
153            }
154            else {
155                minRegularValue = Math.min(minRegularValue, value);
156                maxRegularValue = Math.max(maxRegularValue, value);
157            }
158            minOutlier = Math.min(minOutlier, minRegularValue);
159            maxOutlier = Math.max(maxOutlier, maxRegularValue);
160        }
161
162        return new BoxAndWhiskerItem(new Double(mean), new Double(median),
163                new Double(q1), new Double(q3), new Double(minRegularValue),
164                new Double(maxRegularValue), new Double(minOutlier),
165                new Double(maxOutlier), outliers);
166
167    }
168
169    /**
170     * Calculates the first quartile for a list of numbers in ascending order.
171     * If the items in the list are not in ascending order, the result is
172     * unspecified.  If the list contains items that are <code>null</code>, not
173     * an instance of <code>Number</code>, or equivalent to
174     * <code>Double.NaN</code>, the result is unspecified.
175     *
176     * @param values  the numbers in ascending order (<code>null</code> not
177     *     permitted).
178     *
179     * @return The first quartile.
180     */
181    public static double calculateQ1(List values) {
182        if (values == null) {
183            throw new IllegalArgumentException("Null 'values' argument.");
184        }
185
186        double result = Double.NaN;
187        int count = values.size();
188        if (count > 0) {
189            if (count % 2 == 1) {
190                if (count > 1) {
191                    result = Statistics.calculateMedian(values, 0, count / 2);
192                }
193                else {
194                    result = Statistics.calculateMedian(values, 0, 0);
195                }
196            }
197            else {
198                result = Statistics.calculateMedian(values, 0, count / 2 - 1);
199            }
200
201        }
202        return result;
203    }
204
205    /**
206     * Calculates the third quartile for a list of numbers in ascending order.
207     * If the items in the list are not in ascending order, the result is
208     * unspecified.  If the list contains items that are <code>null</code>, not
209     * an instance of <code>Number</code>, or equivalent to
210     * <code>Double.NaN</code>, the result is unspecified.
211     *
212     * @param values  the list of values (<code>null</code> not permitted).
213     *
214     * @return The third quartile.
215     */
216    public static double calculateQ3(List values) {
217        if (values == null) {
218            throw new IllegalArgumentException("Null 'values' argument.");
219        }
220        double result = Double.NaN;
221        int count = values.size();
222        if (count > 0) {
223            if (count % 2 == 1) {
224                if (count > 1) {
225                    result = Statistics.calculateMedian(values, count / 2,
226                            count - 1);
227                }
228                else {
229                    result = Statistics.calculateMedian(values, 0, 0);
230                }
231            }
232            else {
233                result = Statistics.calculateMedian(values, count / 2,
234                        count - 1);
235            }
236        }
237        return result;
238    }
239
240}