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 }