From b5f542d4a99e0d9e4f0bdb7b9cb215af4c8554f2 Mon Sep 17 00:00:00 2001
From: Vinzent Steinberg <Vinzent.Steinberg@gmail.com>
Date: Fri, 5 May 2017 14:18:09 +0200
Subject: [PATCH] Add a reference

---
 src/lib.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/lib.rs b/src/lib.rs
index de439fc..7139fed 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -39,6 +39,7 @@ impl Average {
 
     /// Add a number to the sequence of which the average is calculated.
     pub fn add(&mut self, x: f64) {
+        // See https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance.
         self.n += 1;
         let delta = x - self.avg;
         self.avg += delta / f64::approx_from(self.n).unwrap();