[FieldTrip] Working with own data format - events

Marco Dahmane marco.dahmane at gmail.com
Wed Mar 16 14:36:38 CET 2011

> Dear Marco,

> 1) You can use Matlab's find-function for this, for instance, use

something like cfg.trials = find(data.trialinfo(:,1) == 1); to select

all trials for which the first row in your trialinfo-matrix equals 1.

The subsequent FT function you call with cfg as its argument will

limit its processing only to the trials you specified.

OK thank you that is exactly what I needed.

> 2) The answer to this question depends a bit on what *you* define

'events' to be. In general, I would say events and trials are not the

same; an event is something like a trigger that might occur in your

data (i.e., something "pinpointable" in time), whereas a trial is a

segment of data (i.e., something that has a duration). Since I do not

know exactly what you mean by 'event' in your question, I cannot

answer it with certainty. However, a possible answer could be: yes,

you could just use ft_redefinetrials again :)

> Do not hesitate to rephrase your question 2, I might be able to give

you some more detailed help.

> Best,


Well it seems we agree on the difference trial/event. For me a trial is the
time from one trigger to the next (hence every trial is associated to a
given condition) .

Events, for me, can be anything happening within a trial (for instance, a
sub-portion of a given trial that I find interesting). Therefore, I would
like to be able to "mark" specific points in one or more given trials, and
use the data delimited by those "marker points" to perform a given
calculation on them.

A (very) simple example of what I want to do would be : given that my trials
are each about 8 seconds long, let's say the region of interest for me spans
from 3s to 6s in every trial subset. How would I write that in FT ?

And what if on certain trials only, I spot a very interesting spike. Does FT
allow me to put an event marker on that specific spike ? If yes, how so?

Am I being any clearer now?

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