From d4fd11fc91bf95aa8991e4bce6147124b9ba52f2 Mon Sep 17 00:00:00 2001
From: dmiller <dmiller@e0a8ed71-7df4-0310-8962-fdc924857419>
Date: Mon, 24 Oct 2016 20:17:07 +0000
Subject: [PATCH] Avoid NaN return from formulas.mean_stddev when array has
 only 1 element

---
 nselib/formulas.lua | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/nselib/formulas.lua b/nselib/formulas.lua
index f2acc620e..25f3c9c54 100644
--- a/nselib/formulas.lua
+++ b/nselib/formulas.lua
@@ -136,7 +136,9 @@ function mean_stddev(t)
   local i, m, s, sigma
 
   if #t == 0 then
-    return 0, nil
+    return nil, nil
+  elseif #t == 1 then
+    return t[1], 0
   end
 
   m = t[1]