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/*
* Copyright (C) 2019, Matthias Sohn <matthias.sohn@sap.com> and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.util;
/**
* Simple double statistics, computed incrementally, variance and standard
* deviation using Welford's online algorithm, see
* https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_online_algorithm
*
* @since 5.1.9
*/
public class Stats {
private int n = 0;
private double avg = 0.0;
private double min = 0.0;
private double max = 0.0;
private double sum = 0.0;
/**
* Add a value
*
* @param x
* value
*/
public void add(double x) {
n++;
min = n == 1 ? x : Math.min(min, x);
max = n == 1 ? x : Math.max(max, x);
double d = x - avg;
avg += d / n;
sum += d * d * (n - 1) / n;
}
/**
* Returns the number of added values
*
* @return the number of added values
*/
public int count() {
return n;
}
/**
* Returns the smallest value added
*
* @return the smallest value added
*/
public double min() {
if (n < 1) {
return Double.NaN;
}
return min;
}
/**
* Returns the biggest value added
*
* @return the biggest value added
*/
public double max() {
if (n < 1) {
return Double.NaN;
}
return max;
}
/**
* Returns the average of the added values
*
* @return the average of the added values
*/
public double avg() {
if (n < 1) {
return Double.NaN;
}
return avg;
}
/**
* Returns the variance of the added values
*
* @return the variance of the added values
*/
public double var() {
if (n < 2) {
return Double.NaN;
}
return sum / (n - 1);
}
/**
* Returns the standard deviation of the added values
*
* @return the standard deviation of the added values
*/
public double stddev() {
return Math.sqrt(this.var());
}
}
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