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MathGroup Archive 2003

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Re: autocorrelation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg44381] Re: autocorrelation
  • From: Mariusz Jankowski<mjankowski at usm.maine.edu>
  • Date: Fri, 7 Nov 2003 05:16:27 -0500 (EST)
  • Organization: University of Maine System testbed server
  • References: <bo5sst$p1$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Mikael, use ListCorrelate, it is substantially faster. Specifically, if x is your image matrix the following will return all the autocorrelation coefficients assuming zero padding at the borders.

ListCorrelate[x,x,{1,1},0]


If you do not need all the coefficients, but only the first nr rows and nc columns, then use 

ListCorrelate[x,x,{nr,nc},0]


Mariusz





>>> Mikael L<lassenmikael at kabelnettet.dk> 11/3/2003 10:40:13 AM >>>
Hi

I have some tiff images where I have to make autocorrelation on. I have
tried it but I think that math. is very slow.

The images/matrix is 480x360 pixels.

I am using fourier transformation and inversfourier transformation to make
the autocorrelation.



Is there any body that has experience with this using mathematica?



best regards



Mikael




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