[FieldTrip] FW: chop_raw cnt data into segments_&ICA

Konstantina Kalogianni K.Kalogianni at tudelft.nl
Wed Apr 3 11:01:26 CEST 2013

Dear fieldtrip users,

I am new to fieldtrip and I have the following issue regarding preprocessing of EEG and ICA.
I want to:

1.       import my .cnt data

2.       chop my file to 5 different files that correspond to each of my tasks

3.       then take one part of my file that correspond to one of my tasks   and filter, demean, rerefernce, resample raw data

4.       ICA raw data

5.       Then define epochs

6.       & then proceed with the rest of the analysis

One of  my tasks has repetitive triggers with the code 1
So I want to take only the part of my  raw data that corresponds to this task(including some ms before the  first trigger and some after  ) and then at a later stage epoch my data.
Should I create one trial_fun that chop my data to 5 datasets corresponding to each task, then call ft_definetrial, then preprocess the data, ICA them and then call again the ft_defientrial  with another trial_fun to chop my data into epochs?
Is that even possible ?

The way I try to do  it now is :
first define trial with :
cfg.trialdef.eventtype      = 'trigger';
cfg.trialdef.eventvalue     = '1'
cfg.trialdef.prestim        = 0.005; % in seconds
cfg.trialdef.poststim       = 0.01; % in seconds
cfg1                        = ft_definetrial(cfg);

Then I call ft_preprocessing(cfg);
with cfg.continuous  = 'yes'; to make sure that when I ll perform ICA it will be on continuous data.

and then  when I run ICA it produces an expected error that  I cannot run ICA on epoched data (it needs raw).

So I have to epoch after the ICA, but how should I select the part that only corresponds to one of my tasks?

Thank you for your time.

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