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<div class="moz-cite-prefix">Dear Fanny,<br>
<br>
I have no experience in using this nonconstant Q wavelet, but I
hope I can shed some light on the terminology.<br>
<br>
</div>
<blockquote
cite="mid:CAFJqoHU7jayrDLzj7iPYgBk9qMcj2w9z_84PxAQd1Gk49MRveQ@mail.gmail.com"
type="cite">"<br>
<i>Time–frequency analysis was performed for<br>
each channel by convolving the data with a complex Morlet<br>
wavelet w(t, f0) having a Gaussian shape in time (σt) and in<br>
frequency (σf) around the center frequency ( f0). Nonconstant<br>
wavelets with Q increasing from f0/σf =8.5 to 13 for frequencies<br>
from 30 to 100 Hz (step size 2 Hz) were used.<br>
</i><br>
"<br>
<br>
<br>
- I don't understand what is <i>f</i><sub>0</sub> and σ<i><sub>f</sub></i><br>
</blockquote>
<br>
If you compute the frequency spectrum of any signal, you will see
some peaks in the frequency spectrum. If you compute the frequency
spectrum of a wavelet, the maximal peak is conventionally called
center frequency. In Matlab, you can obtain the center frequency by
the function 'centfrq'. Note that the center frequency also depends
on the scale of your wavelet.<br>
<br>
Any peak can be wide or narrow, and just like in statistics you can
describe this with the standard deviation. I am not in particular
familiar with<i> σf </i>and the method you are describing, but I
would guess that it is really just the standard deviation, given
that <i>σ </i>is conventionally used to denote the standard
deviation. <br>
<br>
Judging from your questions, without offending, that you are
probably new to the field of wavelets, you should probably start off
with reading more general literature on wavelets. Maybe start off
with Wikipedia:<br>
<a class="moz-txt-link-freetext" href="http://en.wikipedia.org/wiki/Wavelet">http://en.wikipedia.org/wiki/Wavelet</a><br>
<a class="moz-txt-link-freetext" href="http://en.wikipedia.org/wiki/Morlet_wavelet">http://en.wikipedia.org/wiki/Morlet_wavelet</a><br>
<br>
and then go to some more sophisticated literature ;)<br>
<br>
Best,<br>
Jörn<br>
<br>
<br>
<pre class="moz-signature" cols="72">--
Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen
Neuronal Oscillations Group
FieldTrip Development Team
P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands
Contact:
E-Mail: <a class="moz-txt-link-abbreviated" href="mailto:jm.horschig@donders.ru.nl">jm.horschig@donders.ru.nl</a>
Tel: +31-(0)24-36-68493
Web: <a class="moz-txt-link-freetext" href="http://www.ru.nl/donders">http://www.ru.nl/donders</a>
Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands</pre>
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