[Eeglablist] Question about sorting epochs

[Arnaud Delorme]

> I was wondering if you could help me with something. I have EEG datasets
> that need an unconventional treatment before analysis. In this experiment,
> participants hear a beep (event 1), and 2 seconds later, a series of 5
> stimuli are shown, with 1 second of separation in between (events from 2 to
> 6). After pre-processing and epoching, epochs with event label 1 are 2000
> ms long (from 0 to 2000 ms, no stimulus) and the other epochs are 1000 ms
> long (from -500 to +500 ms, where time zero indicates stimulus
> presentation).
> 
> How can I average across all the epochs with event label 1, 2, 3, 4, 5, and
> 6

This is best done by creating an EEGLAB study (which can be created with 1 participant only).
Then you can compare epochs 1, 2, 3, 4, 5 and 6.

> and then copy the epochs with event label 1 to every other epoch so the
> resulting epochs are 2000 ms (duration of epoch 1) + 1000 ms (duration of
> each stimulus epoch)? Thus, we’d have resulting epochs of -2000 ms to +1000
> ms. The objective is to use the epoch with event number 1 as baseline for
> the stimulus-related epochs (event numbers 2, 3, 4, 5, and 6).

This would require a script. 
It is unclear what you are trying to do. If it is a standard ERP baseline, you can extract very long epochs with events 1, 2, 3, 4, 5, and 6 compute the baseline, then extract smaller epochs.

Cheers,

Arno