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Hi Casper,<br>
<br>
On the memory issues, using DPSS tapers on very large segments of
data, while at the same time using cfg.foilim (instead of the more
selective cfg.foi), results in a huge explosion of required memory.
This is so because the amount of tapers for a specified smoothing
increases with the length of the trials, and the same holds for the
amount of estimable frequencies. In your case, it might be easiest
to specify a cfg.foi, instead of cfg.foilim, e.g. cfg.foi = 20:1:200
should already greatly reduce the amount of memory needed.
Increasing the amount of smoothing also greatly increases the amount
of tapers needed. If you are looking for a higher smoothing, and you
still don't have enough memory, you can try to cut your trials in
smaller pieces, or use downsampling (the amount of tapers depends on
the amount of samples used).<br>
<br>
Best,<br>
Roemer<br>
<br>
<br>
<br>
On 12/10/2011 11:40, Casper van Heck wrote:
<blockquote
cite="mid:CAJ7RtRFMroDu6QDPSQJEeNL8Pq104GnbA5iwNAEjuX_-U-bvfA@mail.gmail.com"
type="cite">
<div>
<div>Dear fieldtrippers,</div>
<div><br>
</div>
<div>I've been using Fieldtrip as an Intern for two months now,
and have repeatedly run into a problem when using DPSS. When
using the below settings, the computer locks up within seconds
(although it does seem to do 'something'), stays that way for
up to ten minutes (which is my personal cutoff, where I force
a reboot), and then reports an 'out of memory'.</div>
<div><br>
</div>
<div>cfg.method = 'mtmfft'; </div>
<div>cfg.output = 'pow';</div>
<div>cfg.taper = 'dpss';</div>
<div>cfg.foilim = [20 200];</div>
</div>
<div>
<div>cfg.tapsmofrq = 1;</div>
</div>
<div><br>
</div>
<div>The data fed to ft_freqanalysis is the result of roughly 30
seconds continuous data of a single (originally bipolar) channel
processed by ft_preprocessing.</div>
<div>When using 'hanning' it completes without a hitch, but DPSS
doesn't. I've tried the same thing using a different, more
powerful computer, which succesfully completed 30 seconds using
the above settings, but when setting the tapsmofrq to 3 the RAM
was filled up in a period of a few seconds, and the computer
choked. The 'normal' computer has 2GB of ram, and a dual-core
intel running at 2GHz, and the more powerful computer has 8GB
ram with an quad-core AMD at 3.4GHz. What am I doing wrong? </div>
<div><br>
</div>
<div>Secondly, I was wondering about the 'montage' funcionality,
since I'll be making use of bipolar arrangements, but the
parameters of the montage-structure as defined on <a
moz-do-not-send="true"
href="http://fieldtrip.fcdonders.nl/reference/ft_apply_montage">http://fieldtrip.fcdonders.nl/reference/ft_apply_montage</a> don't
help me much in making one of my own. Would it be possible to
take a look at an existing montage structure, such as the one
referred to on <a moz-do-not-send="true"
href="http://fieldtrip.fcdonders.nl/getting_started/neuralynx_fcdc">http://fieldtrip.fcdonders.nl/getting_started/neuralynx_fcdc</a>?</div>
<div><br>
</div>
<div>Sincerely,</div>
<div><br>
</div>
<div>Casper van Heck </div>
<div> </div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
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</blockquote>
<br>
<div class="moz-signature">-- <br>
<font size="2"><font color="darkblue"><font face="calibri">Roemer
van der Meij M.Sc.<br>
PhD student<br>
Donders Institute for Brain, Cognition and Behaviour<br>
Centre for Cognition<br>
P.O. Box 9104<br>
6500 HE Nijmegen<br>
The Netherlands<br>
Tel: +31(0)24 3655932<br>
E-mail: <a class="moz-txt-link-abbreviated" href="mailto:r.vandermeij@donders.ru.nl">r.vandermeij@donders.ru.nl</a><br>
</font></font></font></div>
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