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


1 /*
2  * Copyright 2003-2004 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 org.apache.commons.math.util.MathUtils;
19 import java.io.Serializable JavaDoc;
20
21 /**
22  *
23  * Abstract Implementation for the {@link StorelessUnivariateStatistic} interface.
24  * <p>
25  * Provides default <code>evaluate()</code> and <code>incrementAll(double[])<code>
26  * implementations.
27  * <p>
28  * <strong>Note that these implementations are not synchronized.</strong>
29  *
30  * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
31  */
32 public abstract class AbstractStorelessUnivariateStatistic
33     extends AbstractUnivariateStatistic
34     implements StorelessUnivariateStatistic, Serializable JavaDoc {
35
36     /** Serialization UID */
37     static final long serialVersionUID = -44915725420072521L;
38     
39     /**
40      * This default implementation calls {@link #clear}, then invokes
41      * {@link #increment} in a loop over the the input array, and then uses
42      * {@link #getResult} to compute the return value.
43      * <p>
44      * Note that this implementation changes the internal state of the
45      * statistic. Its side effects are the same as invoking {@link #clear} and
46      * then {@link #incrementAll(double[])}.
47      * <p>
48      * Implementations may override this method with a more efficient
49      * implementation that works directly with the input array.
50      * <p>
51      * If the array is null, an IllegalArgumentException is thrown.
52      *
53      * @see org.apache.commons.math.stat.descriptive.UnivariateStatistic#evaluate(double[])
54      */
55     public double evaluate(final double[] values) {
56         if (values == null) {
57             throw new IllegalArgumentException JavaDoc("input value array is null");
58         }
59         return evaluate(values, 0, values.length);
60     }
61     
62     /**
63      * This default implementation calls {@link #clear}, then invokes
64      * {@link #increment} in a loop over the specified portion of the input
65      * array, and then uses {@link #getResult} to compute the return value.
66      * <p>
67      * Note that this implementation changes the internal state of the
68      * statistic. Its side effects are the same as invoking {@link #clear} and
69      * then {@link #incrementAll(double[], int, int)}.
70      * <p>
71      * Implementations may override this method with a more efficient
72      * implementation that works directly with the input array.
73      * <p>
74      * If the array is null or the index parameters are not valid, an
75      * IllegalArgumentException is thrown.
76      *
77      * @see org.apache.commons.math.stat.descriptive.UnivariateStatistic#evaluate(double[], int, int)
78      */
79     public double evaluate(final double[] values, final int begin, final int length) {
80         if (test(values, begin, length)) {
81             clear();
82             incrementAll(values, begin, length);
83         }
84         return getResult();
85     }
86
87     /**
88      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear()
89      */
90     public abstract void clear();
91
92     /**
93      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult()
94      */
95     public abstract double getResult();
96
97     /**
98      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double)
99      */
100     public abstract void increment(final double d);
101     
102     /**
103      * This default implementation just calls {@link #increment} in a loop over
104      * the input array.
105      * <p>
106      * Throws IllegalArgumentException if the input values array is null.
107      *
108      * @param values values to add
109      * @throws IllegalArgumentException if values is null
110      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#incrementAll(double[])
111      */
112     public void incrementAll(double[] values) {
113         if (values == null) {
114             throw new IllegalArgumentException JavaDoc("input values array is null");
115         }
116         incrementAll(values, 0, values.length);
117     }
118    
119     /**
120      * This default implementation just calls {@link #increment} in a loop over
121      * the specified portion of the input array.
122      * <p>
123      * Throws IllegalArgumentException if the input values array is null.
124      *
125      * @param values array holding values to add
126      * @param begin index of the first array element to add
127      * @param length number of array elements to add
128      * @throws IllegalArgumentException if values is null
129      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#incrementAll(double[], int, int)
130      */
131     public void incrementAll(double[] values, int begin, int length) {
132         if (test(values, begin, length)) {
133             int k = begin + length;
134             for (int i = begin; i < k; i++) {
135                 increment(values[i]);
136             }
137         }
138     }
139     
140     /**
141      * Returns true iff <code>object</code> is an
142      * <code>AbstractStorelessUnivariateStatistic</code> returning the same
143      * values as this for <code>getResult()</code> and <code>getN()</code>
144      * @param object object to test equality against.
145      * @return true if object returns the same value as this
146      */
147     public boolean equals(Object JavaDoc object) {
148         if (object == this ) {
149             return true;
150         }
151        if (object instanceof AbstractStorelessUnivariateStatistic == false) {
152             return false;
153         }
154         AbstractStorelessUnivariateStatistic stat = (AbstractStorelessUnivariateStatistic) object;
155         return (MathUtils.equals(stat.getResult(), this.getResult()) &&
156                 MathUtils.equals(stat.getN(), this.getN()));
157     }
158     
159     /**
160      * Returns hash code based on getResult() and getN()
161      *
162      * @return hash code
163      */
164     public int hashCode() {
165         return 31* (31 + MathUtils.hash(getResult())) + MathUtils.hash(getN());
166     }
167
168 }
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