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<font face="Courier New, Courier" color="#228B22">Dear FieldTrip
users,<br><br>
I have been playing with the
</font><font face="Courier New, Courier">freqanalysis_wltconvol</font><font face="Courier New, Courier" size=4>
function in hopes of using the morlet wavelet time frequency analysis on
some eeg data. I have been able to get it running, and I find that
it works very quickly, which is great. However, I am hoping some
users or F.T. programmers can explain some of the function inputs and
processing. The cfg example is as follows:<br><br>
</font><font face="Courier New, Courier" color="#228B22">%
cfg.method =
'wltconvol';<br>
%
cfg.foi
= 1:1:100;<br>
% cfg.width =
7;<br>
% or<br>
% cfg.width =
linspace(5,10,length(cfg.foi));<br>
%
cfg.toi
= 0:0.1:2; <br>
% cfg.gwidth =
3;<br><br>
</font><font face="Arial, Helvetica" size=4>I believe that the cfg.width
specifies the number of wave cycles used in each frequency's wavelet
analysis (so at 2Hz, 7 cycles spans 3500ms of data, right?). Maybe
this is not correct, because I do not seem to get the frequencies as low
as I would expect given my data epoch length. Perhaps this has to
do with the cfg.gwidth parameter, which I do not think I completely
understand - what is it? <br><br>
Also, we do not have the matlab wavelet toolbox, and it appears that it
is not required, but how is the morlet wavelet implemented? As I
look through the code I see calls to fft, ifft, and fftshift, but I
wonder how I can give a good technical description of this process if I
find results in a larger data set.<br><br>
Finally, is there a function or a way to compute the frequency bandwidth
based on the cfg inputs, or is there a fix frequency bandwith for each
foi here? I am sure I am confusing a number of things here, so no
response is too simple.<br><br>
Thanks for any advice, please let me know if there is more information I
can give or if I can clarify my questions.<br><br>
Brian</font></body>
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