[Gnuplot-info] Getting Gnuplot to ignore outliers

[Dave H. <da...@ho...>]

Consider the following made-up sequence:

1 2 2 1 3 3 1 10 2 4 1

I have a simple script which mashes out some stats, and amongst other 
things it reports the standard deviation as 2.49 (because of that outlier 
of 10).

If I ignore it, I get a standard deviation of 1, which is a lot closer to 
reality.

Is there some way to get Gnuplot to ignore outliers and substitute 
"missing", or do I have to write some sort of a filter for it?  I can 
understand that the definition of "outlier" is a loose concept, but I'm 
thinking of defining an expected range for that particular column.

The background here is that I've started analysing my daily spam load; 
there's a very-much-prototype graph over on www.horsfall.org/plotspam.pdf 
(80k), and I would very much like to auto-ignore the spike for "Banner" 
(the green one; it's those morons at Security Focus not being able to 
handle my SMTP banner and retrying immediately) and the spike for "Reject" 
(the red one; it's the idiots who treat it as a challenge).

As an aside, I found I had to use a log scale because of the magnitudes 
involved (many attempts but few successes), but it actually turned out 
quite well.

-- 
Dave Horsfall (VK2KFU)  "Bliss is a MacBook with a FreeBSD server."
http://www.horsfall.org/spam.html (and check the home page whilst you're there)