[FieldTrip] ft_definetrial with .nex files

["Jörn M. Horschig"]

Dear Tara,

you define cfg.trialdef.triallength prior to calling ft_definetrial. 
This will cause the trialfunction to not look for events, but cut your 
recorded data into chunks of 3 seconds, independently of the eventtype 
and -value that you specified. The parameters you probably want to use 
instead are cfg.trialdef.poststim and .prestim. Triallength is supposed 
for continuous data without events, e.g. resting state data.

Btw, if you specifiy cfg.trialdef.eventtype='?' you will get a list with 
all events in your data - that way you can make sure that you are 
specifying the correct types or values (alternatively, you could also 
use ft_read_event).

Hope it helps!
Best,
Jörn

On 1/19/2012 10:12 PM, Tara Jacobson wrote:
> Hello,
>
> Does anyone have experience with .nex files?  It seems straight 
> forward to be able to define trials using events in the .nex, but 
> ft_definetrial is not recognizing them as events.
>
> filename =('11-087_12292011.nex')
>
>
> stim30Hz=[27.25275159.26715258.277925357.2887489.303075522.306625621.317425786.335425885.3462984.3569751083.367751149.37491281.38931347.3964251446.407251578.42161644.42881776.4431751875.453951974.464725];
>
> cfg = [];
> cfg.dataset = filename;
>
> cfg.trialdef.triallength=3;
> cfg.trialdef.eventtype=('Event007');
> cfg.trialdef.eventvalue=stim30Hz;
>
> cfg=ft_definetrial(cfg);
>
> filename =
> 11-087_12292011.nex
> Warning: no trialfun was specified, using trialfun_general
> > In ft_definetrial at 95
> evaluating trialfunction 'trialfun_general'
> reading the events from '11-087_12292011.nex'
> found 0 events
> created 676 trials
>
> My question is what are the 676 trials if it found no events?
>
> Can anyone give me some advice?
>
>
> Thanks very much.
>
>
>
>
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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
Tel:    +31-(0)24-36-68493
Web: http://www.ru.nl/donders

Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands

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