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16 package org.apache.commons.math.stat.descriptive.rank;
17
18 import java.io.Serializable;
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: 348519 $ $Date: 2005-11-23 12:12:18 -0700 (Wed, 23 Nov 2005) $
38 */
39 public class Min extends AbstractStorelessUnivariateStatistic implements Serializable {
40
41 /** Serializable version identifier */
42 private 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 if (!Double.isNaN(values[i])) {
118 min = (min < values[i]) ? min : values[i];
119 }
120 }
121 }
122 return min;
123 }
124 }