1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.math.stat.descriptive.rank;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic;
22
23 /**
24 * Returns the minimum of the available values.
25 * <p>
26 * <ul>
27 * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
28 * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
29 * <li>If any of the values equals <code>Double.NEGATIVE_INFINITY</code>,
30 * the result is <code>Double.NEGATIVE_INFINITY.</code></li>
31 * </ul></p>
32 * <p>
33 * <strong>Note that this implementation is not synchronized.</strong> If
34 * multiple threads access an instance of this class concurrently, and at least
35 * one of the threads invokes the <code>increment()</code> or
36 * <code>clear()</code> method, it must be synchronized externally.</p>
37 *
38 * @version $Revision: 617953 $ $Date: 2008-02-02 22:54:00 -0700 (Sat, 02 Feb 2008) $
39 */
40 public class Min extends AbstractStorelessUnivariateStatistic implements Serializable {
41
42 /** Serializable version identifier */
43 private static final long serialVersionUID = -2941995784909003131L;
44
45 /**Number of values that have been added */
46 private long n;
47
48 /**Current value of the statistic */
49 private double value;
50
51 /**
52 * Create a Min instance
53 */
54 public Min() {
55 n = 0;
56 value = Double.NaN;
57 }
58
59 /**
60 * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#increment(double)
61 */
62 public void increment(final double d) {
63 if (d < value || Double.isNaN(value)) {
64 value = d;
65 }
66 n++;
67 }
68
69 /**
70 * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#clear()
71 */
72 public void clear() {
73 value = Double.NaN;
74 n = 0;
75 }
76
77 /**
78 * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getResult()
79 */
80 public double getResult() {
81 return value;
82 }
83
84 /**
85 * @see org.apache.commons.math.stat.descriptive.StorelessUnivariateStatistic#getN()
86 */
87 public long getN() {
88 return n;
89 }
90
91 /**
92 * Returns the minimum of the entries in the specified portion of
93 * the input array, or <code>Double.NaN</code> if the designated subarray
94 * is empty.
95 * <p>
96 * Throws <code>IllegalArgumentException</code> if the array is null or
97 * the array index parameters are not valid.</p>
98 * <p>
99 * <ul>
100 * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
101 * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
102 * <li>If any of the values equals <code>Double.NEGATIVE_INFINITY</code>,
103 * the result is <code>Double.NEGATIVE_INFINITY.</code></li>
104 * </ul> </p>
105 *
106 * @param values the input array
107 * @param begin index of the first array element to include
108 * @param length the number of elements to include
109 * @return the minimum of the values or Double.NaN if length = 0
110 * @throws IllegalArgumentException if the array is null or the array index
111 * parameters are not valid
112 */
113 public double evaluate(final double[] values,final int begin, final int length) {
114 double min = Double.NaN;
115 if (test(values, begin, length)) {
116 min = values[begin];
117 for (int i = begin; i < begin + length; i++) {
118 if (!Double.isNaN(values[i])) {
119 min = (min < values[i]) ? min : values[i];
120 }
121 }
122 }
123 return min;
124 }
125 }