definetrial in CTF-file

J.M. Schoffelen Jan.Schoffelen at FCDONDERS.RU.NL
Thu Jun 30 16:45:43 CEST 2005

Dear Barbara,

Please have a close look at the documentation of definetrial, by typing help
definetrial. I think it is quite clearly documented:

>>From about line 28 it reads:

% Simple trial definitions (e.g. based on a trigger alone) are supported by
% DEFINETRIAL itself. For this, the general and dataformat-independent way
% of handling trials is by relying on the READ_FCDC_EVENT function to
% collect all event information (such as triggers) from your dataset and
% select trials based on those events. This is implemented in DEFINETRIAL as
%   cfg.trialdef.eventtype  = 'string'
%   cfg.trialdef.eventvalue = number, string or list with numbers or strings
%   cfg.trialdef.prestim    = 0.300 latency in seconds (optional)
%   cfg.trialdef.poststim   = 0.700 latency in seconds (optional)

So, this is the most up-to-date implementation of the function,
You have to specify your cfg.trialdef.eventtype as 'frontpanel trigger'.
In this case it selects the triggers from the frontpanel.
Then just take cfg.trialdef.eventvalue = [6] (no ''!). What remains is the
optional time-window with respect to your relevant trigger. This is not
necessary if you have a trial-based collection, as far as I know.

The includeTrigger-field is also usable, but it is only left in for

Hope this helps,



-----Original Message-----
From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf
Of Barbara H ändel
Sent: Thursday, June 30, 2005 3:56 PM
Subject: [FIELDTRIP] definetrial in CTF-file

Hi anyone,
I just started today to use fieldtrip with but already have a
Problem I don't seem to be able to solve myself. So if anyone has some
advice I would be very thankful.

I tried to execute preprocessing.m however when I define my relevant trials


I get the error message that no trials are beeing defined.

Now, looking into the code of definetrial.m in line 407 the variable
“triggerchan” is defined by triggerChan = read_ctf_trigger(cfg.dataset);

The problem is that it seems like that only the “backpanel” is extracted
from read_ctf_trigger however I would need the “frontpanel”. So
definetrial.m later on only finds “triggerchan” with loads of zeros and can
not match my defined trigger.

Is there any reason why only one variable is taken instead of two (as it is
done at line 455 in definetrial.m)?

Thankful for any suggestion,

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