[FieldTrip] Artifact rejection

Stephen Politzer-Ahles spa268 at nyu.edu
Thu Oct 1 12:49:54 CEST 2015

Hello Federica,

Without seeing your code or the error messages you got, I can't tell why
cfg.trl=trl didn't work.

As for the ft_read_data error, this sounds like the baseline specified
might be longer than what's present in your data. You said your data were
previously processed (and I assume epoched) in EEGLAB; what was the length
of the baseline interval you left? For instance, if you left a -200ms
baseline, that means the first trigger in the dataset is occuring at 201 ms
(assuming 1000 Hz sampling). Then if you define a trl structure in
Fieldtrip with a longer baseline (say, 250 ms) and try to read the data,
fieldtrip will try to read 50 ms of data before the actual beginning of the
file, which would cause this error. if this is the case, you'll need to
either use a shorter baseline interval when you define trials in Fieldtrip,
or you'll need to re-process the data in EEGLAB and leave a longer baseline


Stephen Politzer-Ahles
New York University, Abu Dhabi
Neuroscience of Language Lab

> Message: 1
> Date: Wed, 30 Sep 2015 15:31:56 +0200
> From: Federica Mauro <federica.ma at gmail.com>
> To: FieldTrip discussion list <fieldtrip at science.ru.nl>
> Subject: [FieldTrip] Artifact rejection
> Message-ID:
>         <CABX-y5AfeiuZKc=njGEXgZnNm58dfEFbo=
> UvsNRV8KEj2Ei-ww at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
> Hi everybody,
> I'm trying to use Fieldtrip in order to reject automatically artifacts on
> my dataset. I'm working with EEG data previously preprocessed in EEGLAB,
> thus their extension is .set.
> I'm tryng to follow and adapt the tutorial for MEG data at
> http://www.fieldtriptoolbox.org/tutorial/automatic_artifact_rejection, but
> I found some problems.
> 1. It doesn't recognize assignment cfg.trl = trl. For this reason I tried
> to use ft_definetrial in order to get the matrix cfg.trl, but it still
> gives me problems:
> 2. Specifically: Error using ==> ft_read_data at 206 - cannot read data
> before the begin of the file
> Do you have any suggestion?
> Thank you very much in advance!
> Best,
> Federica
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