[Eeglablist] Averaging EEG files with diff channel numbers

[Makoto Miyakoshi]

Dear Ellee,

Unfortunately, EEGLAB does not support that operation.
Using Matlab command line, you can do it as follows. Assuming the data are
already epoched to the same length and data dimensions are ch x time x
epochs,

concantenated_data = cat(3, old_data, new_data(1:64, :, :));

Note that I'm using only the first 64 channels for the new data. Thus the
old and new data epochs are concatenated.
Then take an average across epochs,

erp = mean(concatenated_data, 3);

This 'erp' has 64 channels and average potentials.

Makoto

On Wed, Jan 5, 2022 at 8:15 AM Heloise M De Baun via eeglablist <
eeglablist at sccn.ucsd.edu> wrote:

> Hi,
>
> We are now recording with 64 eeg channels and then 3 extra auxiliary
> channels that have eyetracking information (1 channel for eye x-position, 1
> for y-position, 1 for pupil size). We want to average these eeg files (or
> eventual erp files) with our old eeg files that were recorded with only 64
> channels.
>
> To be clearer, we want to average an eeg file with 67 channels (64 EEG
> channels + 3 aux) with an eeg file with 64 channels (all EEG). Is this
> possible without deleting channels from the 67 channel file?
>
> Best,
> Ellee
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