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Java > Open Source Codes > org > apache > commons > math > stat > descriptive > SummaryStatistics


1 /*
2  * Copyright 2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.math.stat.descriptive;
17
18 import java.io.Serializable JavaDoc;
19
20 import org.apache.commons.discovery.tools.DiscoverClass;
21 import org.apache.commons.math.util.MathUtils;
22
23 /**
24  * Abstract factory class for univariate statistical summaries.
25  *
26  * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
27  */
28 public abstract class SummaryStatistics implements StatisticalSummary, Serializable JavaDoc {
29
30     /** Serialization UID */
31     static final long serialVersionUID = -6400596334135654825L;
32      
33     /**
34      * Create an instance of a <code>SummaryStatistics</code>
35      *
36      * @param cls the type of <code>SummaryStatistics</code> object to
37      * create.
38      * @return a new factory.
39      * @throws InstantiationException is thrown if the object can not be
40      * created.
41      * @throws IllegalAccessException is thrown if the type's default
42      * constructor is not accessible.
43      */
44     public static SummaryStatistics newInstance(Class JavaDoc cls) throws
45         InstantiationException JavaDoc, IllegalAccessException JavaDoc {
46         return (SummaryStatistics)cls.newInstance();
47     }
48     
49     /**
50      * Create an instance of a <code>SummaryStatistics</code>
51      *
52      * @return a new SummaryStatistics instance.
53      */
54     public static SummaryStatistics newInstance() {
55         SummaryStatistics instance = null;
56         try {
57             DiscoverClass dc = new DiscoverClass();
58             instance = (SummaryStatistics) dc.newInstance(
59                 SummaryStatistics.class,
60                 "org.apache.commons.math.stat.descriptive.SummaryStatisticsImpl");
61         } catch(Throwable JavaDoc t) {
62             return new SummaryStatisticsImpl();
63         }
64         return instance;
65     }
66     
67
68     /**
69      * Return a {@link StatisticalSummaryValues} instance reporting current
70      * statistics.
71      *
72      * @return Current values of statistics
73      */
74     public StatisticalSummary getSummary() {
75         return new StatisticalSummaryValues(getMean(), getVariance(), getN(),
76                 getMax(), getMin(), getSum());
77     }
78     
79     /**
80      * Adds the value to the data to be summarized
81      * @param v the value to be added
82      */
83     public abstract void addValue(double v);
84
85     /**
86      * Returns the <a HREF="http://www.xycoon.com/arithmetic_mean.htm">
87      * arithmetic mean </a> of the available values
88      * @return The mean or Double.NaN if no values have been added.
89      */
90     public abstract double getMean();
91
92     /**
93      * Returns the <a HREF="http://www.xycoon.com/geometric_mean.htm">
94      * geometric mean </a> of the available values
95      * @return The geometricMean, Double.NaN if no values have been added,
96      * or if the productof the available values is less than or equal to 0.
97      */
98     public abstract double getGeometricMean();
99
100     /**
101      * Returns the variance of the available values.
102      * @return The variance, Double.NaN if no values have been added
103      * or 0.0 for a single value set.
104      */
105     public abstract double getVariance();
106
107     /**
108      * Returns the standard deviation of the available values.
109      * @return The standard deviation, Double.NaN if no values have been added
110      * or 0.0 for a single value set.
111      */
112     public abstract double getStandardDeviation();
113     
114     /**
115      * Returns the maximum of the available values
116      * @return The max or Double.NaN if no values have been added.
117      */
118     public abstract double getMax();
119
120     /**
121     * Returns the minimum of the available values
122     * @return The min or Double.NaN if no values have been added.
123     */
124     public abstract double getMin();
125
126     /**
127      * Returns the number of available values
128      * @return The number of available values
129      */
130     public abstract long getN();
131
132     /**
133      * Returns the sum of the values that have been added to Univariate.
134      * @return The sum or Double.NaN if no values have been added
135      */
136     public abstract double getSum();
137
138     /**
139      * Returns the sum of the squares of the available values.
140      * @return The sum of the squares or Double.NaN if no
141      * values have been added.
142      */
143     public abstract double getSumsq();
144
145     /**
146      * Resets all statistics
147      */
148     public abstract void clear();
149     
150     /**
151      * Returns true iff <code>object</code> is a <code>SummaryStatistics</code>
152      * instance and all statistics have the same values as this.
153      * @param object the object to test equality against.
154      * @return true if object equals this
155      */
156     public boolean equals(Object JavaDoc object) {
157         if (object == this ) {
158             return true;
159         }
160         if (object instanceof SummaryStatistics == false) {
161             return false;
162         }
163         SummaryStatistics stat = (SummaryStatistics) object;
164         return (MathUtils.equals(stat.getGeometricMean(),
165                 this.getGeometricMean()) &&
166                 MathUtils.equals(stat.getMax(), this.getMax()) &&
167                 MathUtils.equals(stat.getMean(),this.getMean()) &&
168                 MathUtils.equals(stat.getMin(),this.getMin()) &&
169                 MathUtils.equals(stat.getN(), this.getN()) &&
170                 MathUtils.equals(stat.getSum(), this.getSum()) &&
171                 MathUtils.equals(stat.getSumsq(),this.getSumsq()) &&
172                 MathUtils.equals(stat.getVariance(),this.getVariance()));
173     }
174     
175     /**
176      * Returns hash code based on values of statistics
177      *
178      * @return hash code
179      */
180     public int hashCode() {
181         int result = 31 + MathUtils.hash(getGeometricMean());
182         result = result * 31 + MathUtils.hash(getGeometricMean());
183         result = result * 31 + MathUtils.hash(getMax());
184         result = result * 31 + MathUtils.hash(getMean());
185         result = result * 31 + MathUtils.hash(getMin());
186         result = result * 31 + MathUtils.hash(getN());
187         result = result * 31 + MathUtils.hash(getSum());
188         result = result * 31 + MathUtils.hash(getSumsq());
189         result = result * 31 + MathUtils.hash(getVariance());
190         return result;
191     }
192
193 }
194
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