[FieldTrip] Potential bug in trl

["Jörn M. Horschig"]

Dear Davide,

I never worked with trials of different length, however this should be 
straight forward when writing your own trialfun (just as Michael proposed).
In most trialfuns, the trl matrix is constructed by concatenating the 
vectors begsample, endsample and offset. These vectors can have any 
values you want them to have. As a simple example, you can write a 
trialfun that just returns trl = [1 2 1; 400 500 100] (for your 
experiment, you of course want these values to be computed from your 
trigger values).
Is your problem that such a thing does not work? It would be great if 
you give a concrete use-case, or e.g. attach your trialfun.

Best,
Jörn

On 8/4/2011 4:03 PM, Davide Rivolta wrote:
> Thanks Michael,
>  I wrote my own trialfun.
>  The offset would be negative and would have the same lenght of 
> difference between endsample-begsample. This, for each trial, would 
> have a different value.
> It can be a bug. In fact, I tried to vhange the trialfun by leaving 
> the same begsample and endsample, but I put a fixed offset (i.e., 
> -100) and it worked. All the trial was in and not, like with the 
> variable offset, until time = 0.
> Thanks,
> Davide
>
> On Thu, Aug 4, 2011 at 3:55 PM, Michael Wibral <michael.wibral at web.de 
> <mailto:michael.wibral at web.de>> wrote:
>
>     Hi davide,
>
>     I guess in such a case you would have to write your own trial
>     function. However, offset values larger than 0 mean, that the
>     stimulus occured before you start your piece of data - is that
>     really what you wanted ?
>
>     Michael
>
>
>         ------------------------------------------------------------------------
>         *Von:* "Davide Rivolta" <drivolta81 at gmail.com
>         <mailto:drivolta81 at gmail.com>>
>         *Gesendet:* Aug 4, 2011 2:44:08 PM
>         *An:* fieldtrip at donders.ru.nl <mailto:fieldtrip at donders.ru.nl>
>         *Betreff:* [FieldTrip] Potential bug in trl
>
>
>         Dear all,
>         I have noticed that the trial definition works well when
>         begsample, ensample and offset have fixed values.
>         I have however a specific trialfunction, where each trial has
>         a different lenght.
>         This works well when you specify a fixed offset, however, when
>         even the offset has to change for each trial, Fieldtrip
>         reports values until 0. It ignores time after 0.
>         Might it be a bug?
>         Thanks,
>         Davide
>
>
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>
>
>
> -- 
> Davide Rivolta, PhD
>
>
>
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-- 
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: jm.horschig at donders.ru.nl
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