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*Subject*: Re: efficient kernel or masking algorithm ? UPDATE*From*: Craig Markwardt <craigmnet(at)cow.physics.wisc.edu>*Date*: 25 Feb 2001 14:39:02 -0600*Newsgroups*: comp.lang.idl-pvwave*Organization*: U. Wisc. Madison Physics -- Compact Objects*References*: <Kocm6.25536$MN.621469@news2-win.server.ntlworld.com>*Reply-To*: craigmnet(at)cow.physics.wisc.edu*Xref*: news.doit.wisc.edu comp.lang.idl-pvwave:23658

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

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