|author||Avery Pennarun <firstname.lastname@example.org>||Sat Apr 06 00:03:37 2013 -0400|
|committer||Avery Pennarun <email@example.com>||Sat Apr 06 00:03:37 2013 -0400|
headgrid: handle situations where the stddev is zero. Basically this is a "nulls and dots" graph. nulls don't count toward stddev, so we were dividing by zero.