[Eeglablist] Saving an EEGLAB dataset in a single file

Makoto Miyakoshi mmiyakoshi at ucsd.edu
Mon Jan 4 11:05:03 PST 2021

Dear Arno,

I often use pop_loadset(..., 'loadmode', 'info') because so that I can skip
loading the EEG.data (.fdt).
As long as you leave the option of saving fdt+set files, I have no problem.
Thank you for developing EEGLAB.


On Sun, Dec 27, 2020 at 8:47 AM Delorme, Arnaud <adelorme at ucsd.edu> wrote:

> In EEGLAB 2021 to be released next year, we propose to change the default
> behavior for saving data files.
> The reason for saving two files (a .set and a .fdt file) in EEGLAB is
> mostly historical. Although there has always been an option to save a
> single .set file, this was not the default behavior. In the old days,
> reading one channel was advantageous for group analysis and avoided reading
> the whole file. However, EEGLAB handles group analysis files differently
> now, and there is no advantage to have two files. The other advantage of
> having two files is to be able to quickly read metadata when working with
> an EEGLAB STUDY. However, there is a workaround as explained below.
> So we propose to save as a single .set file by default that will contain
> both the data and the metadata. We will keep the option to save datasets as
> two files (but it will not be the default).
> It is simpler and less confusing to have one file than to have two files.
> This also facilitates compatibility and cross-talk with other software and
> languages.
> Another backward compatible change we want to implement is to save the EEG
> structure's content instead of the EEG structure itself.
> Pseudo code for current implementation
> save -mat myfile.set EEG
> Pseudo code for new implementation
> save -mat myfile.set -struct EEG
> Even old versions of EEGLAB support reading both file formats. The
> advantage of the second implementation is that it is then possible to
> import EEGLAB .set file while omitting the data field (for quickly loading
> an EEGLAB STUDY) using commands such as
> EEG = load('-mat', ‘myfile.set', '-regexp', '^((?!data).)*$’);
> Let us know your thoughts and comments,
> Arno
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