[FieldTrip] Working with own data format - events

jan-mathijs schoffelen jan.schoffelen at donders.ru.nl
Wed Mar 16 08:56:45 CET 2011

Dear Marco,

I am glad to hear that your efforts so far were successful. Sorry to  
hear that you got stuck but it sounds as if you're really almost  
there. I will update the documentation shortly, but this is what you  
need to do:

You can create a field called 'trialinfo', i.e. data.trialinfo in  
which you can store trial-specific information in a NxM matrix, N  
being the number of trials, M can be an arbitrary number of columns.  
In your case you can specify a column vector with the condition  
numbers per trial.
No need to create an event structure or so.

I hope this helps.


On Mar 16, 2011, at 1:43 AM, Marco Dahmane wrote:

> Dear FieldTrippers,
> I have a question that will probably sound trivial to you, but I  
> haven't been able to find the answer anywhere so I will ask it here.  
> Please bear with me as I am all new to FieldTrip and EEG/MEG analysis.
> The data I am working with is in a format that is not recognized  
> natively by FT. I do however possess a MATLAB routine that allows me  
> to read it and store it in a .mat file.
> I have followed the steps described in the FAQ, and reformatted that  
> data within Matlab into a datastructure that is compatible with  
> FieldTrip, first as one big trial then split it with ft_redefinetrial.
> So far so good, as I can visualize my data trial by trial with no  
> problem.
> Now however, I would like to create my own events relative to a set  
> condition. My data is not marked at all so I have to do it "by hand".
> I actually have 6 different experimental conditions and each one of  
> the trials corresponds to the MEG response under one of those  
> conditions.
> How exactly would I go about setting that up in FT ? How do I create  
> events that do not exist in my data?
> In other words, how do I give a value to each trial (assuming I know  
> which trial number relates to which condition)?
> It wasn't clear from the tutorials since all the data used always  
> possesses event data beforehand.
> Thank you in advance,
> Marco
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Dr. J.M. (Jan-Mathijs) Schoffelen
Donders Institute for Brain, Cognition and Behaviour,
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands
J.Schoffelen at donders.ru.nl
Telephone: 0031-24-3614793

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