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Re: need to calculate autocorrelation length of a matrix


From: Matt Foster
Subject: Re: need to calculate autocorrelation length of a matrix
Date: Thu, 26 Jun 2008 14:21:37 +0100

On Wed, Jun 18, 2008 at 12:05 AM, chaski <address@hidden> wrote:
>
> Working with a n x n matrix of non-negative real values, I'm trying to
> calculate a 2d analog of 'autocorrelation length' -- that is, I want to find
> the minimum euclidean (or similar) distance at which, on average, two
> entries in the matrix (separated by that critical distance) will show a
> mutual correlation of less than 1/e (or 1/2, or some other such 'natural'
> threshold).
>
> Analogous measures are used as metrics of landscape 'ruggedness' or
> 'roughness', I think, but I've looked in vain for an established method to
> calculate them. Does anyone know of a script that could (perhaps with
> tweaking at my novice level) be used to do so?
>

I did a quick google, and found this:
http://scien.stanford.edu/class/psych221/projects/00/jichien/matlab/AutoCorr2.m
Which you might be able to adapt to your needs.

I've also attached a couple of functions that I wrote a while ago, and
which might be useful.
I've not ever used them in anger, but the algorithm is from a
textbook, and they give the same results as the example in the book.

Cheers,

Matt
-- 
Matt Foster | http://my-mili.eu/matt

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