Find global rejection threshold¶

This example demonstrates how to use autoreject to find global rejection thresholds.

# Author: Mainak Jas <mainak.jas@telecom-paristech.fr>
# License: BSD (3-clause)

Let us import the data using MNE-Python and epoch it.

import mne
from mne import io
from mne.datasets import sample

event_id = {'Visual/Left': 3}
tmin, tmax = -0.2, 0.5

data_path = sample.data_path()
raw_fname = data_path + '/MEG/sample/sample_audvis_filt-0-40_raw.fif'
event_fname = data_path + ('/MEG/sample/sample_audvis_filt-0-40_raw-'
                           'eve.fif')

raw = io.read_raw_fif(raw_fname, preload=True)
events = mne.read_events(event_fname)

include = []
picks = mne.pick_types(raw.info, meg=True, eeg=True, stim=False,
                       eog=True, include=include, exclude='bads')
epochs = mne.Epochs(raw, events, event_id, tmin, tmax,
                    picks=picks, baseline=(None, 0), preload=True,
                    reject=None, verbose=False, detrend=1)

Out:

Opening raw data file /Users/mainak/mne_data/MNE-sample-data/MEG/sample/sample_audvis_filt-0-40_raw.fif...
    Read a total of 4 projection items:
        PCA-v1 (1 x 102)  idle
        PCA-v2 (1 x 102)  idle
        PCA-v3 (1 x 102)  idle
        Average EEG reference (1 x 60)  idle
    Range : 6450 ... 48149 =     42.956 ...   320.665 secs
Ready.
Current compensation grade : 0
Reading 0 ... 41699  =      0.000 ...   277.709 secs...

Now we get the rejection dictionary

from autoreject import get_rejection_threshold  # noqa

# We can use the `decim` parameter to only take every nth time slice.
# This speeds up the computation time. Note however that for low sampling
# rates and high decimation parameters, you might not detect "peaky artifacts"
# (with a fast timecourse) in your data. A low amount of decimation however is
# almost always beneficial at no decrease of accuracy.
reject = get_rejection_threshold(epochs, decim=2)

Out:

/Users/mainak/Documents/github_repos/autoreject/autoreject/autoreject.py:219: RuntimeWarning: The measurement information indicates a low-pass frequency of 40 Hz. The decim=2 parameter will result in a sampling frequency of 75.0769 Hz, which can cause aliasing artifacts.
  epochs.decimate(decim=decim)
Estimating rejection dictionary for mag
Estimating rejection dictionary for grad
Estimating rejection dictionary for eeg
Estimating rejection dictionary for eog

and print it

print('The rejection dictionary is %s' % reject)

Out:

The rejection dictionary is {'mag': 3.2845860018518954e-12, 'grad': 1.0357642173052411e-10, 'eeg': 5.740583629141964e-05, 'eog': 4.4772763304005286e-05}

Finally, the cleaned epochs

epochs.drop_bad(reject=reject)
epochs.average().plot()

../_images/sphx_glr_plot_estimate_global_reject_001.png

Total running time of the script: ( 0 minutes 4.259 seconds)

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