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<div class="moz-cite-prefix">Hi Danja,<br>
<br>
you can could either compute the average yourself:<br>
<i><small>data.avg = squeeze(nanmean(data.trial, 1));<br>
data.dimord = 'chan_time';</small></i><br>
Note that the covariance might be invalid here, not sure what
ft_regressconfound does here.<br>
<br>
or call <small><i>data = ft_checkdata(data, 'datatype', 'raw')</i></small>
which converts the timelocked data back to raw data format, and
you can call <small><i>ft_timelockanalysis </i></small>again
with <small><i>cfg.keeptrials = 'no'</i></small> (the latter
would be my favourite)<br>
<br>
Regarding the planar gradient, I'd say no. Keep in mind that the
planar gradient computation results in all values > 0, thus
e.g. noise might not cancel out as efficiently and a simple t-test
against with the classical null hypothesis becomes invalid. I
don't do ERP analysis though, so if someone can provide a good
reason for doing the transformation nonetheless, I might be
convinced otherwise ;)<br>
<br>
Best,<br>
Jörn<br>
<br>
On 7/20/2012 7:48 AM, Porada Danja wrote:<br>
</div>
<blockquote cite="mid:0D507729-5866-4635-845A-E5C45F210830@uos.de"
type="cite">
<pre wrap="">Hi,
I would like to compute a grand average of the individual ERFs after I already used ft_regressconfounds (in order to deal with changes in head position during the experiment).
Here is the problem:
For regressing out head position confounds I have to keep the individual trials during the timelockanalysis. But for computing the grand average afterwards I need averages and not individual trials. Which is the best way to obtain the average?
And I have another question: Do I have to calculate the planar gradient before computing the grand average?
Best,
Danja
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<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
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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