events_from_annotations doesn't return relative offset

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1
  • MNE version: 1.7.1
  • operating system: windows 10

Hi, I want to find the index/offset of certain events using MNE. I started from the annotations and find the events like below:

event5,_=mne.events_from_annotations(raw3,regexp='5')

However, the event5[0] not the true offset, and to get the true offset, I also need to do below:

event5=event5[:,0]-[raw3.first_samp]*len(event5)

Is this the right behavior? I thought the events are the latency and offset has been counted already.

Best,
Long

2

Hi @Long

I’m not sure what you mean - I don’t think I can replicate the behavior you are describing using MNE’s sample dataset:

fname = mne.datasets.sample.data_path() / 'MEG' / 'sample' /  'sample_audvis_raw.fif'
raw = mne.io.read_raw(fname)
raw.annotations.append(onset=1, duration=1, description="TEST")
print(raw.info["sfreq"])  # 600.61 Hz
print(raw.first_samp)  #  25800
print(raw.annotations.onset)  # [1.] seconds

events, _ = mne.events_from_annotations(raw)

print(events)  # array([[601,   0,   1]])

# Convert samples to seconds
events[:, 0] / raw.info["sfreq"]  # array([1.00064103]) ... seconds

It seems to me that MNE returns event onsets in samples relative to 0 seconds, which is exactly what I would expect. Is this not what you are expecting or wanting for your data?