BUG: read_epochs for split files has incorrect events

[emilyps14]

I have a large epochs file, that gets split into two files when I call epochs.save()
When I load it again using mne.read_epochs(), the events corresponding to the second file are incorrect, offset by [last epoch from the first file + tmax + 10s].

The bug comes from _concatenate_epochs.

This breaks the relationship between the raw file and the events list, which (aside from causing downstream problems with my code) can lead to an error in epochs.get_data if the data were loaded with preload=False.

[agramfort]

can you share a code snippet to replicate usings sample data? you can make random events if it's just for testing.

[emilyps14]

`
import os.path as op
import mne

data_path = op.join(mne.datasets.sample.data_path(), 'MEG', 'sample')
raw = mne.io.read_raw_fif(op.join(data_path, 'sample_audvis_raw.fif'), preload=True)

events = mne.make_fixed_length_events(raw,1)
epochs = mne.Epochs(raw, events)
epochs.save('test-epo.fif',split_size='100MB')

epochs2 = mne.read_epochs('test-epo.fif',preload=False)
epochs2.get_data() # throws error
assert(all([e1==e2 for e1,e2 in zip(epochs.events[:,0],epochs2.events[:,0])])) # assertion error
`

[agramfort]

I don't think @larsoner is good enough to fix this :)

[larsoner]

I see what you did there :)

Yes I can try hopefully next week

[larsoner]

@emilyps14 can you see if #5103 fixes it for you?

[emilyps14]

Yep, that fixes it. Thanks!