<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi Aaron (et al.)<div><br></div><div>another way to filter the whole recording is the workaround using EEGlab.</div><div>By default, you always read in the whole recording in EEGlab and apply all filters to the whole recording.</div><div>After filtering, you can use eeglab2fieldtrip.m to move your filtered data from EEGlab to field trip.</div><div><br></div><div>Note however, that Jörn's concern regarding your memory still applies. Also, filtering the whole recording takes quite some time.</div><div><br></div><div>Best,</div><div><br></div><div>Julian</div><div><br><div><div>Am 05.07.2013 um 08:41 schrieb Jörn M. Horschig:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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<div class="moz-cite-prefix">Hi Aaron,<br>
<br>
in that case you need to define only one trial, going from 0 to
the end of the recording and call ft_preprocessing. Not sure if
this will work, but something like<br>
<br>
<small><i> cfg = [];</i><i><br>
</i><i> ...</i><i><br>
</i><i> hdr = ft_read_header(cfg.dataset);</i><i><br>
</i><i> cfg.trl = [0 hdr.nSamples 0];</i><i><br>
</i><i> data = ft_preprocessing(cfg);</i></small><br>
<br>
Subsequently you might want to try using ft_redefinetrial to get
the epochs you are interested in.<br>
<br>
Note however that you need to have sufficient memory for reading
all your data in. I am not sure how much memory you have, how long
your recording is, how high your sampling rate and how many
channels you have. If Matlab crashes when reading in everything,
you would need to use trialpadding, or need to think of something
clever yourself :)<br>
<br>
Would be great if you could let us know how you solve this in the
end so that we can refer to that if someone else in future has a
similar question.<br>
<br>
Best,<br>
Jörn<br>
On 7/5/2013 3:51 AM, Aaron Schurger wrote:<br>
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<blockquote cite="mid:CALeeyASfgLOQJHLfse5Fa0EXZn7Q8f1xmPLZLHQwcZRRDkQr0A@mail.gmail.com" type="cite">
<pre wrap="">Thanks, Thomas. What if I wanted to apply the filtering to the entire
time series first, and then extract the trial epochs after filtering?
Is there a way to do that?
Thanks,
Aaron
On Thu, Jul 4, 2013 at 4:31 PM, Thomas Hartmann
<a class="moz-txt-link-rfc2396E" href="mailto:thomas.hartmann@th-ht.de"><thomas.hartmann@th-ht.de></a> wrote:
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<pre wrap="">hi aaron,
filtering is generally applied after the data have been epoched. to avoid
the filter artifacts you are speaking about, we normally define epochs that
are sufficiently larger so that these artifacts would be in data we are not
interested in. about 1s at both ends of the epoch should be enough in most
cases. but you better check... later you can use ft_redefinetrial to discard
that extra data.
hope this helps.
best,
thomas
Aaron Schurger <a class="moz-txt-link-rfc2396E" href="mailto:aaron.schurger@gmail.com"><aaron.schurger@gmail.com></a> schrieb:
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<blockquote type="cite">
<pre wrap="">Hi,
When you read in a data file using ft_preprocessing, with high-pass
filtering, is the high-pass filter applied before the data are epoched
(i.e. on the entire time series for the whole data file), or is the
high-pass filter applied separately to each epoch? For very low
frequencies (with period longer than one data epoch) this will make a
difference.
Thanks!
Aaron
--
Aaron Schurger, PhD
Post-doctoral researcher
INSERM U992 / NeuroSpin
CEA - Saclay, France
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<pre wrap="">
Dr. Thomas Hartmann
CIMeC - Center for Mind/Brain Sciences
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<pre wrap="">
</pre>
</blockquote>
<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
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