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<div class="moz-cite-prefix">HI Daniel,<br>
<br>
thanks for reporting this. Strange error... but it should not be
related to having timepoint before 0. The fix of the time-axis in
raw2timelock was implemented because of numerical inaccuracies
that can occur across trials. For example, some trials might start
at -0.24999 others at -0.25 (this can happen during acquisition or
during resampling, etc., also computers make errors, especially
when dealing with decimals). When computing a common time-axis,
Matlab would compare these two values and treat them as two
samples before 0 rather than 1 (which strictly speaking is true).
So a common time-axis needs to be build, which is invariant to
small differences. Unfortunately, that was not very trivial to
accomplish. I've build a test scripts which tests very many
different cases for which this function works fine. So first, just
to be sure, are you using the most recent version of FieldTrip?<br>
<br>
Most colleagues in our group including myself are interested in
the prestimulus period, so if this was a trivial error, we
probably would have found it long time ago ;) However, it might be
that it indeed breaks with your data nonetheless due to some
reason. Since this might be specific to some few datasets, it
would be great if you could send me a snippet of your data (like
one or two trials) together with some lines of code to reproduce
this error. It is quite nasty to debug this stuff, so in order to
not keep you from doing research, just go ahead with the fix you
implemented for this one dataset, but be aware that I am pretty
sure that it will break for other datasets ;)<br>
<br>
Best regards,<br>
Jörn<br>
<br>
<br>
On 3/18/2013 7:18 PM, Daniel Stolzberg wrote:<br>
</div>
<blockquote
cite="mid:CAF_tj0eXNStmO8vnNz75NFBbMpK9gc=WjqjM-qd3xSYYMpD84Q@mail.gmail.com"
type="cite">
<div dir="ltr">Hello,
<div><br>
</div>
<div>I have been working with continuous data trials which begin
before the trigger occurs (ex: [-0.25 1.0] sec) and have run
into a snag when using ft_singleplotER. The error occurs in
the raw2timelock subfunction of ft_checkdata after calling
ft_singleplotER with a time axis that includes pre-trigger
(i.e. < 0) time points. This error may not be for
ft_singleplotER, but it is the function I was trying to use.<br
clear="all">
<div><br>
</div>
<div style="">Here is the error:</div>
<div style="">
<div>> Subscripted assignment dimension mismatch.</div>
<div>> </div>
<div>> Error in ft_checkdata>raw2timelock (line 1753)</div>
<div>> tmptrial(i,:,begsmp(i):endsmp(i)) =
data.trial{i};</div>
<div>> <br>
</div>
<div>> Error in ft_checkdata (line 302)</div>
<div>> data = raw2timelock(data);</div>
<div>> <br>
</div>
<div>> Error in ft_singleplotER (line 186)</div>
<div>> varargin{i} = ft_checkdata(varargin{i},
'datatype', {'timelock', 'freq'});</div>
<div><br>
</div>
<div style="">After some debugging, I found that the number
of samples used to (re)generate the time vector is always
1 sample too small if there are negative time values. I
assume that this is because the time point 0 is not being
considered (?). By adding the following line to
raw2timelock in ft_checkdata of the most recent build, I
was able to get around any errors in this subfunction and
all is now copacetic:</div>
</div>
<div><br>
</div>
<div>
<div>line 1740: nsmp = nsmp + any(time<0); % <---
acounting for timepoint at 0?</div>
</div>
<div><br>
</div>
<div style="">I don't know if anyone else has run into this
problem but I thought I would share this with the community.</div>
<div style=""><br>
</div>
<div style="">Regards,</div>
<div style="">Dan</div>
<div style=""><br>
</div>
-- <br>
<div dir="ltr">Daniel Stolzberg, PhD
<div>Post-doctoral Fellow</div>
<div>Cerebral Systems Laboratory</div>
<div>Department of Physiology and Pharmacology</div>
<div>Schulich School of Medicine & Dentistry</div>
<div>University of Western Ontario</div>
<div><a moz-do-not-send="true"
href="http://www.cerebralsystems.ca/" target="_blank">http://www.cerebralsystems.ca/</a><br>
</div>
</div>
</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
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</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
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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