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