ENH: Preserve annotations in epochs

Describe the new feature or enhancement

Is there a way to map annotations from the raw dataset onto the AverageTFR object? Since the tfr is occurring over windows, then the time scale of the annotations from the original time scale are inherently different.

E.g. if I have an event at sample 10000, with sfreq=1000, then it occurs at 10 seconds into the raw dataset. If i have an averageTFR that was computed with a moving window of say 1 second step size, then the new sample point of the event would be 10.

Describe your proposed implementation

Ideally this would consist of two things that I could see being useful:

1. A public function map_annotations_to_sfreq that allows mapping Annotations to different time-scales based on a passed say… sfreq value. So based on the above example, if I wanted to map Annotations that are based on sfreq=1000Hz, to some tfr object with sfreq=1 Hz, then I would somehow pass that information to map_annotations_to_sfreq that returns me a new Annotations object that has onset and duration in the new time-scale.

2. Use the public function above to make AverageTFR, or EpochsTFR, etc. to keep their Annotations when the time-scale changes.

I strongly would prefer having 1 because besides mne-python objects, I create other derivatives of the raw data that inherently have a “sliding” window component to them, and hence change the time-scale in the same way as a sliding FFT would.

Additional comments

@larsoner’s comment on gitter for reference:

@adam2392 in principle we should be able to do that at least for EpochsTFR, can you open an issue feature request? For AverageTFR I'm not sure because we don't preserve annotations in Evoked even (just Raw and Epochs) so we'd probably want to do that first before doing it for AverageTFR

[drammock]

by the dev meeting you mean the office hours announced on MNE discourse or something else? I’d be interested to join.

on discord, but separate from the office hours. I didn’t find you in a search of the discord users, ping me there and I’ll fill you in.

[larsoner]

I think we’ll want some time to fully test + implement this (including viz) so I think this shouldn’t go into 0.24 but rather 0.25/1.0