1 package org.lcsim.recon.tracking.trfutil;
2 //**********************************************************************
3
4 // Return a weighted average.
5 public class WAvg
6 {
7
8 private double _sum0;
9 private double _sum1;
10 private double _sum2;
11 private int _count;
12
13 public WAvg()
14 {
15 _sum0= 0.0;
16 _sum1=0.0;
17 _sum2=0.0;
18 _count=0;
19 }
20
21 // input is value and square of the uncertainty
22 public void addPair(double val, double err)
23 {
24 double weight = 1.0/err;
25 _sum0 += weight;
26 _sum1 += weight*val;
27 _sum2 += weight*val*val;
28 ++_count;
29 }
30 public int count()
31 {
32 return _count;
33 }
34 public double average()
35 {
36 return _sum1/_sum0;
37 }
38 public double error()
39 {
40 return 1.0/_sum0;
41 }
42 public double chiSquared()
43 {
44 return _sum2 - _sum1*_sum1/_sum0;
45 }
46
47
48 public String toString()
49 {
50 return "Weighted average = " + average()
51 + " +/- " + Math.sqrt(error())
52 + " (err = " + error() + ")"
53 + "\n Chi-square = " + chiSquared();
54
55 }
56 }