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Java > Open Source Codes > org > apache > commons > math > stat > descriptive > rank > Max


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.rank;
17
18 import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
19
20 /**
21  * Returns the maximum of the available values.
22  * <p>
23  * <ul>
24  * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
25  * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
26  * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
27  * the result is <code>Double.POSITIVE_INFINITY.</code></li>
28  * </ul>
29 * <p>
30  * <strong>Note that this implementation is not synchronized.</strong> If
31  * multiple threads access an instance of this class concurrently, and at least
32  * one of the threads invokes the <code>increment()</code> or
33  * <code>clear()</code> method, it must be synchronized externally.
34  *
35  * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
36  */
37 public class Max extends AbstractStorelessUnivariateStatistic {
38
39     /** Serializable version identifier */
40     static final long serialVersionUID = -5593383832225844641L;
41     
42     /** Number of values that have been added */
43     private long n;
44         
45     /** Current value of the statistic */
46     private double value;
47
48     /**
49      * Create a Max instance
50      */
51     public Max() {
52         n = 0;
53         value = Double.NaN;
54     }
55     
56     /**
57      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double)
58      */
59     public void increment(final double d) {
60         if (d > value || Double.isNaN(value)) {
61             value = d;
62         }
63         n++;
64     }
65
66     /**
67          * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear()
68          */
69     public void clear() {
70         value = Double.NaN;
71         n = 0;
72     }
73
74     /**
75      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult()
76      */
77     public double getResult() {
78         return value;
79     }
80
81     /**
82      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getN()
83      */
84     public long getN() {
85         return n;
86     }
87     
88     /**
89      * Returns the maximum of the entries in the specified portion of
90      * the input array, or <code>Double.NaN</code> if the designated subarray
91      * is empty.
92      * <p>
93      * Throws <code>IllegalArgumentException</code> if the array is null or
94      * the array index parameters are not valid.
95      * <p>
96      * <ul>
97      * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
98      * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
99      * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
100      * the result is <code>Double.POSITIVE_INFINITY.</code></li>
101      * </ul>
102      *
103      * @param values the input array
104      * @param begin index of the first array element to include
105      * @param length the number of elements to include
106      * @return the maximum of the values or Double.NaN if length = 0
107      * @throws IllegalArgumentException if the array is null or the array index
108      * parameters are not valid
109      */
110     public double evaluate(final double[] values, final int begin, final int length) {
111         double max = Double.NaN;
112         if (test(values, begin, length)) {
113             max = values[begin];
114             for (int i = begin; i < begin + length; i++) {
115                 max = (max > values[i]) ? max : values[i];
116             }
117         }
118         return max;
119     }
120 }
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