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


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 java.io.Serializable JavaDoc;
19
20 import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
21
22 /**
23  * Returns the minimum of the available values.
24  * <p>
25  * <ul>
26  * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
27  * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
28  * <li>If any of the values equals <code>Double.NEGATIVE_INFINITY</code>,
29  * the result is <code>Double.NEGATIVE_INFINITY.</code></li>
30  * </ul>
31  * <p>
32  * <strong>Note that this implementation is not synchronized.</strong> If
33  * multiple threads access an instance of this class concurrently, and at least
34  * one of the threads invokes the <code>increment()</code> or
35  * <code>clear()</code> method, it must be synchronized externally.
36  *
37  * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
38  */
39 public class Min extends AbstractStorelessUnivariateStatistic implements Serializable JavaDoc {
40
41     /** Serializable version identifier */
42     static final long serialVersionUID = -2941995784909003131L;
43       
44     /**Number of values that have been added */
45     private long n;
46     
47     /**Current value of the statistic */
48     private double value;
49
50     /**
51      * Create a Min instance
52      */
53     public Min() {
54         n = 0;
55         value = Double.NaN;
56     }
57     
58     /**
59      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double)
60      */
61     public void increment(final double d) {
62         if (d < value || Double.isNaN(value)) {
63             value = d;
64         }
65         n++;
66     }
67
68     /**
69      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear()
70      */
71     public void clear() {
72         value = Double.NaN;
73         n = 0;
74     }
75
76     /**
77      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult()
78      */
79     public double getResult() {
80         return value;
81     }
82
83     /**
84      * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getN()
85      */
86     public long getN() {
87         return n;
88     }
89     
90     /**
91      * Returns the minimum of the entries in the specified portion of
92      * the input array, or <code>Double.NaN</code> if the designated subarray
93      * is empty.
94      * <p>
95      * Throws <code>IllegalArgumentException</code> if the array is null or
96      * the array index parameters are not valid.
97      * <p>
98      * <ul>
99      * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
100      * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
101      * <li>If any of the values equals <code>Double.NEGATIVE_INFINITY</code>,
102      * the result is <code>Double.NEGATIVE_INFINITY.</code></li>
103      * </ul>
104      *
105      * @param values the input array
106      * @param begin index of the first array element to include
107      * @param length the number of elements to include
108      * @return the minimum of the values or Double.NaN if length = 0
109      * @throws IllegalArgumentException if the array is null or the array index
110      * parameters are not valid
111      */
112     public double evaluate(final double[] values,final int begin, final int length) {
113         double min = Double.NaN;
114         if (test(values, begin, length)) {
115             min = values[begin];
116             for (int i = begin; i < begin + length; i++) {
117                 min = (min < values[i]) ? min : values[i];
118             }
119         }
120         return min;
121     }
122 }
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