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One of my students wrote a C program a few years ago which did autocorrelation 
(I think using a 'multiple Tau' algorithm), taking data from a digital 
counter, and was reasonably fast. If you are interested, please contact me off 
the list.
Sudipta
On Tue, 14 Jun 2011 14:40:26 -0700, David Baddeley wrote
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> 
> It's been a while since I used matlab, but the other classic way to 
> speed up correlation is to use FFTs  - ie: corr = 
> ifftshift(real(ifft(fft(x)*fft(flipud(x)))))
> 
> you can also replace fft(flipud(x)) with ifft(x) (subject to 
> normalisation), which will avoid a couple of memory allocations.
> 
> this method should be significantly faster (O(nlogn)) than a 
> standard correlation (O(n^2)), but you might need to mess around a 
> bit with normalisation and cut out just the bit of the curve 
> corresponding to +ve lags.
> 
> I have a funny feeling that this might already be available as a 
> function 
> (potentially called fftcorr), but can't be sure.
> 
> cheers,
> David
> 
> ----- Original Message ----LISTS.UMN.EDU
> Sent: Wed, 15 June, 2011 1:08:38 AM
> Subject: Re: FCS - Matlab code
> 
> *****
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> 
> Have you looked at this? (I found it with google)
> 
> http://www.mathworks.com/matlabcentral/fileexchange/22358
> 
> Cheers
> On 14/06/2011, at 12:27 PM, Alessandro Esposito wrote:
> 
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > *****
> > 
> > Dear all, 
> >    I was trying to write code for FCS analysis in Matlab, but noticed that 
> > computing the ACF directly is computationally very expensive. I've read 
papers
> 
> > about the math needed to make the problem computationally efficient, but 
not 
> > intending to develop new FCS methods I am not that keen committing too 
much 
> > time into that.
> > 
> > Does anyone have Matlab code for FCS analysis. If you have a toolbox 
great, if
> 
> > you have just the optimized functions to compute the correlation functions 
for
> 
> > FCS and FCCS, it will be anyway VERY helpful.
> > 
> > Cheers, 
> > 
> > Alessandro
> > www.quantitative-microscopy.org


Dr. Sudipta Maiti
Associate Professor
Dept. of Chemical Sciences
Tata Institute of Fundamental Research
Homi Bhabha Raod, Colaba, Mumbai 400005
Ph. 91-22-2278-2716 / 2539
Fax: 91-22-2280-4610
alternate e-mail: [log in to unmask]
url: biophotonics.wetpaint.com