Adding overlap keyword to make_fixed_length_epochs

Describe the new feature or enhancement

I am trying to use time-frequency analysis that is present in mne without converting to arrays first. There is no way to do this using the Raw object, and one must convert to Epochs, with each epoch “representing” the window that will have tfr methods applied. E.g. I want to compute the multitaper FFT, and/or morlet wavelet transform to get an AverageTfr object for multiple frequency bands, alpha, beta, gamma, etc.

Normally, one would like some overlap of these windows. For example, if you do multitpaer FFT, then you usually use a sliding window with some overlap (e.g. 1 sec window with 0.5 sec step).

In https://mne.tools/stable/generated/mne.make_fixed_length_events.html#mne.make_fixed_length_events there is an overlap keyword.

However, in make_fixed_legnth_epochs there is not. https://mne.tools/stable/generated/mne.make_fixed_length_epochs.html#mne.make_fixed_length_epochs

Describe your proposed implementation

Is it possible to add the overlap keyword argument here?

Describe possible alternatives

I’m still not quite sure what the optimal way to apply tfr analysis to a Raw object. Obviously one can always convert to arrays, but then they lose the structure present in the mne data structures. I would prefer staying with the data structures mne has (e.g. Epochs for TFR). If what I said up there is not the optimal way to construct TFR then please let me know.

Additional comments

I can update an existing example to show this functionality off if needed.

[agramfort]

try to cook something for your needs and share it when it does the job for you.

then we’ll see what to consider for inclusion in mne

[agramfort]

my concern is that TFRs are often bigger than the initial raw data (one signal gives an image), so it makes sense to compute it on the fly when you need and do not store it to disk. A TFR for 300 MEG channels for 6 mins of sample data would be huge.