Potential bug in eeglabio exporting

[Andesha]

Description of the problem

When exporting an epochs object via eeglabio, all events when loaded into MATLAB are marked as dummy events, or fails to pass checkset.

Steps to reproduce

# This requires my data file of course

epochs = mne.read_epochs('working_mne.fif')
epochs.export('problematic_eeglab.set', overwrite=True)

# Then load via pop_loadset in latest matlab/eeglab

Link to data

https://drive.google.com/file/d/1U3HptLod9yCUd7YebKnGSaWK8RqfUmkh/view?usp=sharing

Expected results

Replicating the event names in MATLAB.

Actual results

See screenshot.

Additional information

Platform Linux-6.14.0-36-generic-x86_64-with-glibc2.39
Python 3.12.3 (main, Nov 6 2025, 13:44:16) [GCC 13.3.0]
Executable /home/tyler/.cache/uv/builds-v0/.tmpV89SPU/bin/python
CPU Intel(R) Core(TM) Ultra 7 155U (14 cores)
Memory 30.9 GiB

Core
├☑ mne 1.11.0 (latest release)
├☑ numpy 1.26.4 (OpenBLAS 0.3.23.dev with 14 threads)
├☑ scipy 1.16.3
└☑ matplotlib 3.10.7 (backend=module://matplotlib_inline.backend_inline)

Numerical (optional)
├☑ sklearn 1.7.2
├☑ pandas 2.3.3
└☐ unavailable numba, nibabel, nilearn, dipy, openmeeg, cupy, h5io, h5py

Visualization (optional)
├☑ ipywidgets 8.1.8
└☐ unavailable pyvista, pyvistaqt, vtk, qtpy, ipympl, pyqtgraph, mne-qt-browser, trame_client, trame_server, trame_vtk, trame_vuetify

Ecosystem (optional)
├☑ mne-bids 0.17.0
├☑ mne-icalabel 0.8.1
├☑ eeglabio 0.1.2
├☑ edfio 0.4.11
├☑ defusedxml 0.7.1

[welcome]

Hello! 👋 Thanks for opening your first issue here! ❤️ We will try to get back to you soon. 🚴

[scott-huberty]

Hey @Andesha !

Do you have any hypotheses about where things are going wrong? I wonder if it has something to do with these warnings which are generated when I export the file you shared, particularly the last warning message...

import mne

ep_bug = mne.read_epochs("/path/to/mne-bug/working_mne.fif")
ep_bug.export("foo.set")

/Users/scotterik/devel/repos/eeglabio/eeglabio/epochs.py:125 EEGLABIO: WARNING: Invalid event latencies, ignored for export.
/Users/scotterik/devel/repos/eeglabio/eeglabio/epochs.py:162 EEGLABIO: WARNING: Events doesn't meet the requirement of at least one event per epoch, adding dummy events

[Andesha]

I did poke around in that part of the code but it didn't illuminate anything for me.

These files are the result of merged files at one point but I don't think that should change anything,

[Andesha]

any news or any support I can give on this?

[larsoner]

I have not had a chance to check -- @scott-huberty do you have time to look into the potential fix here? If not I can get to it but maybe not until after holidays

[scott-huberty]

@Andesha given you have the time, if you are able to 1) identify the cause of the bug (likely a line in the eeglabio codebase), just let us know so that we know what to fix, or 2) you can open a PR with a fix and we can iterate from there!

If not, I can also take a closer look but I also am unlikely to get to it until after the holidays.