<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
Hi Vladimir, <br>
<br>
Well, it wasn't that final yet, I actually meant to sent the e-mail to
dev-mailing list ;). I had a short discussion with Jan-Mathijs on it,
but since it wasn't going live yet it didn't matter that much. The
tapsmofrq being variable I realized doesn't necessarily mean different
number of tapers, so I will implement that in the new-implementation
tomorrow (tiny changes). However, implementing variable number of
tapers requires some more thorough design decisions for the new
low-level functions (especially in terms of consistent data
representation throughout all low-level functions). Perhaps we should
discuss this in more detail in the dev-mailing list? I'm sure
Jan-Mathijs will join, Robert is on vacation at the moment. <br>
<br>
But thanks for your reply!<br>
<br>
<br>
Best,<br>
Roemer<br>
<br>
<br>
<br>
<br>
On 7/27/2010 4:58 PM, Vladimir Litvak wrote:
<blockquote
cite="mid:AANLkTi=AJy3L+o-TsQ5XnQaJoydbAHSwroZbiaC3Njjp@mail.gmail.com"
type="cite">Dear Roemer,
<div><br>
</div>
<div>Why did you decide to drop the support for variable number of
tapers in mtmconvol? That was actually quite a handy feature that I'm
using to get TFs with more or less uniform smoothness across frequency.
I don't know how many other people are using it but if there are many
perhaps we can campaign for retaining it in the new implementation ;-)</div>
<div><br>
</div>
<div>Best,</div>
<div><br>
</div>
<div>Vladimir<br>
<br>
<div class="gmail_quote">On Tue, Jul 27, 2010 at 3:48 PM, Roemer van
der Meij <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:r.vandermeij@donders.ru.nl">r.vandermeij@donders.ru.nl</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000">
Hi everybody,<br>
<br>
I just finished fully implementing the new low-level frequency analysis
routines for cfg.method = mtmconvol and mtmfft. They are not yet used
by default, and I would appreciate if it can be tested more before
optimizing computation speeds (should be relatively equal now, but many
optimizations possible). <br>
<br>
The new routines can be used by adding a third input argument to your
ft_freqanalysis calls, as:<br>
New implementation:<br>
freq = ft_freqanalysis(cfg,data,1)<br>
Old implementation (default):<br>
freq = ft_freqanalysis(cfg,data,0)<br>
<br>
<b>Things that are different:</b><br>
- all mtmconvol output is now phase-shifted such that an angle of 0 of
any fourier-coefficient <i>always </i>means a peak of an oscillation
in the data, and an angle of pi will <i>always</i> mean the trough of
an oscillation (wavelet wise angle = 0 is implemented as cosine at
peak, and sine in up-going flank)<br>
- all mtmfft output is now phase-shifted such that any angle from any
fourier-coefficient is from the perspective of the oscillation in the
data being at its peak at time = 0<br>
- mtmconvol now uses an accurate frequency vector for building its
wavelets (determined by fsample and nsample, with cfg.foi as starting
point), instead of an <i>uncorrected</i> cfg.foi (mtmfft already used
an accurate one) (note: this causes slight differences between the old
and new implementation)<br>
- mtmfft can now take a cfg.foi input-vector as well, instead of the
usual cfg.foilim (backwards compatible)<br>
- because of the above, nearly <i>all</i> fourier-output is different,
but e.g. phase differences between coefficients should be the same<br>
- we decided to drop the support for variable number of tapers in
mtmconvol, cfg.tapsmofrq can only be a scalar now (warning is given,
and first element of vector is selected)<br>
- in the new format, many things can be upgraded/implemented etc. in
the future<br>
<br>
<br>
As freqanalysis is a rather fundamental pilar of FieldTrip, I would
really appreciate if some of you can do some testing based on the above
differences and anything else you can think of. Different types of
data, different approaches, etc. to see if both implementations give
comparable results and such (do note raw fourier-coefficients will
almost always be different). It could be I missed some fields from the
old functions that I diligently checked, or made some errors that did
not affect my current testing environment.<br>
I can be reached at the e-mail address below, via the mailing-list, or
via bug-reports. Thanks in advance.<br>
<br>
All the best!<br>
<br>
Roemer<br>
<br>
<br>
PS: the changes will be on the ft-server tonight, but are of course
already in the svn-version<br>
<pre cols="72">--
Roemer van der Meij MSc
PhD student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognition
P.O. Box 9104
6500 HE Nijmegen
The Netherlands
Tel: +31(0)24 3655932
E-mail: <a moz-do-not-send="true"
href="mailto:r.vandermeij@donders.ru.nl" target="_blank">r.vandermeij@donders.ru.nl</a></pre>
</div>
<p>----------------------------------</p>
<p>The aim of this list is to facilitate the discussion between
users of the FieldTrip toolbox, to share experiences and to discuss new
ideas for MEG and EEG analysis.</p>
<p> <a moz-do-not-send="true"
href="http://listserv.surfnet.nl/archives/fieldtrip.html"
target="_blank">http://listserv.surfnet.nl/archives/fieldtrip.html</a></p>
<p> <a moz-do-not-send="true"
href="http://www.ru.nl/fcdonders/fieldtrip/" target="_blank">http://www.ru.nl/fcdonders/fieldtrip/</a></p>
</blockquote>
</div>
<br>
</div>
<p>----------------------------------</p>
<p>The aim of this list is to facilitate the discussion between users
of the FieldTrip toolbox, to share experiences and to discuss new ideas
for MEG and EEG analysis.</p>
<p> <a class="moz-txt-link-freetext" href="http://listserv.surfnet.nl/archives/fieldtrip.html">http://listserv.surfnet.nl/archives/fieldtrip.html</a></p>
<p> <a class="moz-txt-link-freetext" href="http://www.ru.nl/fcdonders/fieldtrip/">http://www.ru.nl/fcdonders/fieldtrip/</a></p>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Roemer van der Meij MSc
PhD student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognition
P.O. Box 9104
6500 HE Nijmegen
The Netherlands
Tel: +31(0)24 3655932
E-mail: <a class="moz-txt-link-abbreviated" href="mailto:r.vandermeij@donders.ru.nl">r.vandermeij@donders.ru.nl</a></pre>
</body>
</html>
<p>----------------------------------</p>
<p>The aim of this list is to facilitate the discussion between users of the FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis.</p>
<p> http://listserv.surfnet.nl/archives/fieldtrip.html</p>
<p> http://www.ru.nl/fcdonders/fieldtrip/</p>