[Eeglablist] Delete data from (the middle of) epochs

[Arnaud Delorme]

Hi Sebastian,

I see what you want to do. A few directions:

1. Extract large epochs and remove the baseline of your choice. Then re-epoch the data (you can extract epochs from data that is already epoched).

2. Do not delete baseline. Simply high pass your data (at 0.5 Hz for example) then extract epochs. That will solve the baseline problem.

3. If you use ERSP, you can use time warping feature.

4. Use scripting to achieve your goal.

Best wishes,

Arno

> On Oct 15, 2018, at 1:49 PM, Sebastian Sauppe <sauppe.s at gmail.com> wrote:
> 
> Dear EEGLAB list members,
> 
> is it possible to delete segments of data for already epoched data?
> 
> I am trying to do a rather unconventional thing that, however, makes sense for my project. I have EEG data from an experiment where participants listened to sentences and I want to extract two different kinds of epochs (time locked to different points in the sentences). I first extracted epochs that are long enough to have all data points for both kinds of time-locking and used these epochs for ICA and artifact correction. These epochs are already time-locked to the first event of interest. The second event of interest occurs at different times in different epochs and I know how to shift the event markers so that I can time-lock to this second event.
> 
> However, I need to take a segment before the first event as the baseline. When I simply shift the events with different latencies in different trials its not straightforward to keep the baseline segment. So I was thinking that the easiest way would be to just delete the data points between the first event and the second event so that the epoch goes from 
> 
> data_pre-event1
> event1
> data_between_event1_and_event2
> event2
> data_post-event2
> 
> to
> 
> data_pre-event1
> event2
> data_post-event2
> 
> The resulting epochs would then all be of the same length again (200 ms baseline and 1000 ms after event2).
> 
> I didn’t find any command that would accomplish this. Does anyone of you know how to cut out data points from epochs?
> 
> Unfortunately, subtracting the baseline before shifting the event triggers is not an option because I want to follow Alday’s recommendation of not subtracting the baseline but including it as a predictor in a regression model (https://arxiv.org/abs/1707.08152).
> 
> Regards,
> Sebastian
> 
> -----------
> Dr. Sebastian Sauppe
> Department of Comparative Linguistics, University of Zurich
> Homepage: https://sites.google.com/site/sauppes/
> Twitter: @SebastianSauppe
> Google Scholar Citations: https://scholar.google.de/citations?user=wEtciKQAAAAJ 
> ResearchGate: http://www.researchgate.net/profile/Sebastian_Sauppe
> ORCID ID: http://orcid.org/0000-0001-8670-8197
> 
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