annotating bad segments, then cropping signal, annotations don't get shifted?

Support & Discussions
1

MNE 1.9.0

Hi MNE Team,

I manually annotated bad segments in patient EEG data.
Next, I cropped the early and late parts of the resting state data, as they were most noisy.
I assumed that the annotations in the remaining time window would be shifted accordingly. Luckily, my colleague compared the pre/post cropping annotations and noted that they didn`t get shifted. There is probably a good reason for this behaviour, which I am curious to hear about.
I suggest a warning that cautions the user that annotations are not updated automatically when cropping signals containing annotations. I think that can be easily implemented and might prevent users from potentially rejecting good segments and keeping bad segments.

Happy to hear your thoughts.

Cheers,

Carina

2

Hello, simply speaking, annotation onset times are stored as the time of day. They’re not based on time relative to recording onset.

So if a recording starts at 09:00.00 and an annotation is added for a segment 10 mins after recording start, it will be tied to 09:10.00.

If you crop, say, the first five minutes, it only “takes” 5 min (instead of previously 10) to “reach” the annotation.

This is intentional behavior, though.

A fix I could imagine for your use case is opti ally adjusting the recording start time if one crops a segment from the beginning of the recording.

Richard

3

Then again, perhaps we are already shifting onset when cropping, and this is exactly what’s causing your issue? Could you please provide a reproducible example that demonstrates the issue?

Richard

4

I think annotations should get shifted accordingly when cropping. If this is not the case, please open an issue.