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Re: efficient kernel or masking algorithm ? UPDATE

"Martin Downing" <martin.downing@ntlworld.com> writes:

> I was wandering through new Craig's IDL archive site (which is brilliant by
> the way) and came across this question asking for an efficient way of
> calculating the loacal standard deviation in an array. It seemed to me that
> the thread had not reached a full solution so perhaps some of you might be
> interested in this method which is very fast. It is based on the crafty
> formula for variance:
>   variance = (sum of the squares)/n + (square of the sums)/n*n
> [ apologies if this is going over old ground !]

Hi Martin--

This looks like a great way to do things.  Now if we could only
translate those bloomin' British English spellings! NEIGHBOURHOOD
indeed. :-)

As a side note, I believe that your message would have actually shown
up as a reply to Richard's or JD's messages in the archive, if you had
placed the Message-ID of their article in the References header of
yours.  I've tried it here.  We'll see if it works.


Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response