[FieldTrip] wavelet analysis

Manuel Mercier manuel.mercier at einstein.yu.edu
Sat Jun 18 11:09:55 CEST 2011


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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