1 /*
2 * Copyright (C) 2019, Matthias Sohn <matthias.sohn@sap.com>
3 * and other copyright owners as documented in the project's IP log.
4 *
5 * This program and the accompanying materials are made available
6 * under the terms of the Eclipse Distribution License v1.0 which
7 * accompanies this distribution, is reproduced below, and is
8 * available at http://www.eclipse.org/org/documents/edl-v10.php
9 *
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or
13 * without modification, are permitted provided that the following
14 * conditions are met:
15 *
16 * - Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials provided
22 * with the distribution.
23 *
24 * - Neither the name of the Eclipse Foundation, Inc. nor the
25 * names of its contributors may be used to endorse or promote
26 * products derived from this software without specific prior
27 * written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 */
43 package org.eclipse.jgit.util;
44
45 /**
46 * Simple double statistics, computed incrementally, variance and standard
47 * deviation using Welford's online algorithm, see
48 * https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_online_algorithm
49 *
50 * @since 5.1.9
51 */
52 public class Stats {
53 private int n = 0;
54
55 private double avg = 0.0;
56
57 private double min = 0.0;
58
59 private double max = 0.0;
60
61 private double sum = 0.0;
62
63 /**
64 * Add a value
65 *
66 * @param x
67 * value
68 */
69 public void add(double x) {
70 n++;
71 min = n == 1 ? x : Math.min(min, x);
72 max = n == 1 ? x : Math.max(max, x);
73 double d = x - avg;
74 avg += d / n;
75 sum += d * d * (n - 1) / n;
76 }
77
78 /**
79 * @return number of the added values
80 */
81 public int count() {
82 return n;
83 }
84
85 /**
86 * @return minimum of the added values
87 */
88 public double min() {
89 if (n < 1) {
90 return Double.NaN;
91 }
92 return min;
93 }
94
95 /**
96 * @return maximum of the added values
97 */
98 public double max() {
99 if (n < 1) {
100 return Double.NaN;
101 }
102 return max;
103 }
104
105 /**
106 * @return average of the added values
107 */
108
109 public double avg() {
110 if (n < 1) {
111 return Double.NaN;
112 }
113 return avg;
114 }
115
116 /**
117 * @return variance of the added values
118 */
119 public double var() {
120 if (n < 2) {
121 return Double.NaN;
122 }
123 return sum / (n - 1);
124 }
125
126 /**
127 * @return standard deviation of the added values
128 */
129 public double stddev() {
130 return Math.sqrt(this.var());
131 }
132 }