[FieldTrip] wavelet analysis

jan-mathijs schoffelen jan.schoffelen at donders.ru.nl
Tue Jun 21 09:08:34 CEST 2011

Dear Manuel,

Thanks for your message. I gave the faq a good read, and I agree that  
the answer can be made a bit more clear. I updated the faqs you  
mentioned and hope that this explains the issue better.

Let me know if it is still not clear.

Best wishes,


On Jun 18, 2011, at 11:09 AM, Manuel Mercier wrote:

> Dear Field-trippers
> I recently ran some time frequency analysis using the wavelet method.
> I was surprise to see that whereas I asked for a step of 1Hz, it was  
> not
> the case every alternate step (for foi=2:1:10 ; I got [2 3.2 4 5.2 6  
> 7.2 8
> 9.2 10]), and it was also the case when I changed the toi (2.5, 1.5  
> with
> constant trials length of 2.5 sec and sampling freq 1000Hz).
> I found a kind of explanation following the faq
> (http://fieldtrip.fcdonders.nl/faq/why_does_my_output.freq_not_match_my_cfg.foi_when_using_wavelet_formerly_wltconvol_in_ft_freqanalyis 
> ).
> Still it is not clear to me why this refers to Fourier transform.
>> From my (none specialist) point of view it is possible to produce a
> wavelet of any size (Hz;Dt).
> It is clear that there is some limitations based on the duration of  
> the
> epochs and the number of time points. But in the present case it  
> shouldn't
> be a problem, is it?
>     Would be please if someone can help me with this issue.
>     Thanks in advance
>     Manuel
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Dr. J.M. (Jan-Mathijs) Schoffelen
Donders Institute for Brain, Cognition and Behaviour,
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands
J.Schoffelen at donders.ru.nl
Telephone: 0031-24-3614793

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