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%matplotlib inline
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# Authors: Denis Engemann <denis.engemann@gmail.com>
# Alexandre Gramfort <alexandre.gramfort@telecom-paristech.fr>
#
# License: BSD (3-clause)
import numpy as np
import mne
from mne.preprocessing import ICA
from mne.preprocessing import create_ecg_epochs, create_eog_epochs
from mne.datasets import sample
Setup paths and prepare raw data.
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data_path = sample.data_path()
raw_fname = data_path + '/MEG/sample/sample_audvis_filt-0-40_raw.fif'
raw = mne.io.read_raw_fif(raw_fname, preload=True)
raw.filter(1, None, fir_design='firwin') # already lowpassed @ 40
raw.annotations = mne.Annotations([1], [10], 'BAD')
raw.plot(block=True)
# For the sake of example we annotate first 10 seconds of the recording as
# 'BAD'. This part of data is excluded from the ICA decomposition by default.
# To turn this behavior off, pass ``reject_by_annotation=False`` to
# :meth:`mne.preprocessing.ICA.fit`.
raw.annotations = mne.Annotations([0], [10], 'BAD')
1) Fit ICA model using the FastICA algorithm.
Other available choices are picard, infomax or extended-infomax.
The default method in MNE is FastICA, which along with Infomax is one of the most widely used ICA algorithm. Picard is a new algorithm that is expected to converge faster than FastICA and Infomax, especially when the aim is to recover accurate maps with a low tolerance parameter, see [1]_ for more information.
We pass a float value between 0 and 1 to select n_components based on the percentage of variance explained by the PCA components.
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ica = ICA(n_components=0.95, method='fastica', random_state=0, max_iter=100)
picks = mne.pick_types(raw.info, meg=True, eeg=False, eog=False,
stim=False, exclude='bads')
ica.fit(raw, picks=picks, decim=3, reject=dict(mag=4e-12, grad=4000e-13),
verbose='warning') # low iterations -> does not fully converge
# maximum number of components to reject
n_max_ecg, n_max_eog = 3, 1 # here we don't expect horizontal EOG components
2) identify bad components by analyzing latent sources.
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title = 'Sources related to %s artifacts (red)'
# generate ECG epochs use detection via phase statistics
ecg_epochs = create_ecg_epochs(raw, tmin=-.5, tmax=.5, picks=picks)
ecg_inds, scores = ica.find_bads_ecg(ecg_epochs, method='ctps')
ica.plot_scores(scores, exclude=ecg_inds, title=title % 'ecg', labels='ecg')
show_picks = np.abs(scores).argsort()[::-1][:5]
ica.plot_sources(raw, show_picks, exclude=ecg_inds, title=title % 'ecg')
ica.plot_components(ecg_inds, title=title % 'ecg', colorbar=True)
ecg_inds = ecg_inds[:n_max_ecg]
ica.exclude += ecg_inds
# detect EOG by correlation
eog_inds, scores = ica.find_bads_eog(raw)
ica.plot_scores(scores, exclude=eog_inds, title=title % 'eog', labels='eog')
show_picks = np.abs(scores).argsort()[::-1][:5]
ica.plot_sources(raw, show_picks, exclude=eog_inds, title=title % 'eog')
ica.plot_components(eog_inds, title=title % 'eog', colorbar=True)
eog_inds = eog_inds[:n_max_eog]
ica.exclude += eog_inds
3) Assess component selection and unmixing quality.
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# estimate average artifact
ecg_evoked = ecg_epochs.average()
ica.plot_sources(ecg_evoked, exclude=ecg_inds) # plot ECG sources + selection
ica.plot_overlay(ecg_evoked, exclude=ecg_inds) # plot ECG cleaning
eog_evoked = create_eog_epochs(raw, tmin=-.5, tmax=.5, picks=picks).average()
ica.plot_sources(eog_evoked, exclude=eog_inds) # plot EOG sources + selection
ica.plot_overlay(eog_evoked, exclude=eog_inds) # plot EOG cleaning
# check the amplitudes do not change
ica.plot_overlay(raw) # EOG artifacts remain
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# To save an ICA solution you can say:
# ica.save('my_ica.fif')
# You can later load the solution by saying:
# from mne.preprocessing import read_ica
# read_ica('my_ica.fif')
# Apply the solution to Raw, Epochs or Evoked like this:
# ica.apply(epochs)