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import numpy as np
from nose.tools import (assert_raises, assert_equal, assert_almost_equal,
assert_true)
from numpy.testing import assert_array_equal
from os import path as op
import warnings
import mne
from mne.io import Raw
from mne.utils import sum_squared
from mne.time_frequency import compute_epochs_csd, induced_power
warnings.simplefilter('always')
base_dir = op.join(op.dirname(__file__), '..', '..', 'io', 'tests', 'data')
raw_fname = op.join(base_dir, 'test_raw.fif')
event_fname = op.join(base_dir, 'test-eve.fif')
def _get_data():
# Read raw data
raw = Raw(raw_fname)
raw.info['bads'] = ['MEG 2443', 'EEG 053'] # 2 bads channels
# Set picks
picks = mne.pick_types(raw.info, meg=True, eeg=False, eog=False,
stim=False, exclude='bads')
# Read several epochs
event_id, tmin, tmax = 1, -0.2, 0.5
events = mne.read_events(event_fname)[0:100]
epochs = mne.Epochs(raw, events, event_id, tmin, tmax, proj=True,
picks=picks, baseline=(None, 0), preload=True,
reject=dict(grad=4000e-13, mag=4e-12))
# Create an epochs object with one epoch and one channel of artificial data
event_id, tmin, tmax = 1, 0.0, 1.0
epochs_sin = mne.Epochs(raw, events[0:5], event_id, tmin, tmax, proj=True,
picks=[0], baseline=(None, 0), preload=True,
reject=dict(grad=4000e-13))
freq = 10
epochs_sin._data = np.sin(2 * np.pi * freq
* epochs_sin.times)[None, None, :]
return epochs, epochs_sin
def test_compute_epochs_csd():
"""Test computing cross-spectral density from epochs
"""
epochs, epochs_sin = _get_data()
# Check that wrong parameters are recognized
assert_raises(ValueError, compute_epochs_csd, epochs, mode='notamode')
assert_raises(ValueError, compute_epochs_csd, epochs, fmin=20, fmax=10)
assert_raises(ValueError, compute_epochs_csd, epochs, fmin=20, fmax=20.1)
assert_raises(ValueError, compute_epochs_csd, epochs, tmin=0.15, tmax=0.1)
assert_raises(ValueError, compute_epochs_csd, epochs, tmin=0, tmax=10)
assert_raises(ValueError, compute_epochs_csd, epochs, tmin=10, tmax=11)
data_csd_mt = compute_epochs_csd(epochs, mode='multitaper', fmin=8,
fmax=12, tmin=0.04, tmax=0.15)
data_csd_fourier = compute_epochs_csd(epochs, mode='fourier', fmin=8,
fmax=12, tmin=0.04, tmax=0.15)
# Check shape of the CSD matrix
n_chan = len(data_csd_mt.ch_names)
assert_equal(data_csd_mt.data.shape, (n_chan, n_chan))
assert_equal(data_csd_fourier.data.shape, (n_chan, n_chan))
# Check if the CSD matrix is hermitian
assert_array_equal(np.tril(data_csd_mt.data).T.conj(),
np.triu(data_csd_mt.data))
assert_array_equal(np.tril(data_csd_fourier.data).T.conj(),
np.triu(data_csd_fourier.data))
# Computing induced power for comparison
epochs.crop(tmin=0.04, tmax=0.15)
with warnings.catch_warnings(record=True): # deprecation
warnings.simplefilter('always')
power, _ = induced_power(epochs.get_data(), epochs.info['sfreq'], [10],
n_cycles=0.6)
power = np.mean(power, 2)
# Maximum PSD should occur for specific channel
max_ch_power = power.argmax()
max_ch_mt = data_csd_mt.data.diagonal().argmax()
max_ch_fourier = data_csd_fourier.data.diagonal().argmax()
assert_equal(max_ch_mt, max_ch_power)
assert_equal(max_ch_fourier, max_ch_power)
# Maximum CSD should occur for specific channel
ch_csd_mt = [np.abs(data_csd_mt.data[max_ch_power][i])
if i != max_ch_power else 0 for i in range(n_chan)]
max_ch_csd_mt = np.argmax(ch_csd_mt)
ch_csd_fourier = [np.abs(data_csd_fourier.data[max_ch_power][i])
if i != max_ch_power else 0 for i in range(n_chan)]
max_ch_csd_fourier = np.argmax(ch_csd_fourier)
assert_equal(max_ch_csd_mt, max_ch_csd_fourier)
# Check a list of CSD matrices is returned for multiple frequencies within
# a given range when fsum=False
csd_fsum = compute_epochs_csd(epochs, mode='fourier', fmin=8, fmax=20,
fsum=True)
csds = compute_epochs_csd(epochs, mode='fourier', fmin=8, fmax=20,
fsum=False)
freqs = [csd.frequencies[0] for csd in csds]
csd_sum = np.zeros_like(csd_fsum.data)
for csd in csds:
csd_sum += csd.data
assert(len(csds) == 2)
assert(len(csd_fsum.frequencies) == 2)
assert_array_equal(csd_fsum.frequencies, freqs)
assert_array_equal(csd_fsum.data, csd_sum)
def test_compute_epochs_csd_on_artificial_data():
"""Test computing CSD on artificial data
"""
epochs, epochs_sin = _get_data()
sfreq = epochs_sin.info['sfreq']
# Computing signal power in the time domain
signal_power = sum_squared(epochs_sin._data)
signal_power_per_sample = signal_power / len(epochs_sin.times)
# Computing signal power in the frequency domain
data_csd_fourier = compute_epochs_csd(epochs_sin, mode='fourier')
data_csd_mt = compute_epochs_csd(epochs_sin, mode='multitaper')
fourier_power = np.abs(data_csd_fourier.data[0, 0]) * sfreq
mt_power = np.abs(data_csd_mt.data[0, 0]) * sfreq
assert_true(abs(fourier_power - signal_power) <= 0.5)
assert_true(abs(mt_power - signal_power) <= 1)
# Power per sample should not depend on time window length
for tmax in [0.2, 0.4, 0.6, 0.8]:
for add_n_fft in [30, 0, 30]:
t_mask = (epochs_sin.times >= 0) & (epochs_sin.times <= tmax)
n_samples = sum(t_mask)
n_fft = n_samples + add_n_fft
data_csd_fourier = compute_epochs_csd(epochs_sin, mode='fourier',
tmin=None, tmax=tmax, fmin=0,
fmax=np.inf, n_fft=n_fft)
fourier_power_per_sample = np.abs(data_csd_fourier.data[0, 0]) *\
sfreq / data_csd_fourier.n_fft
assert_true(abs(signal_power_per_sample -
fourier_power_per_sample) < 0.003)
# Power per sample should not depend on number of tapers
for n_tapers in [1, 2, 3, 5]:
for add_n_fft in [30, 0, 30]:
mt_bandwidth = sfreq / float(n_samples) * (n_tapers + 1)
data_csd_mt = compute_epochs_csd(epochs_sin, mode='multitaper',
tmin=None, tmax=tmax, fmin=0,
fmax=np.inf,
mt_bandwidth=mt_bandwidth,
n_fft=n_fft)
mt_power_per_sample = np.abs(data_csd_mt.data[0, 0]) *\
sfreq / data_csd_mt.n_fft
# The estimate of power gets worse for small time windows when
# more tapers are used
if n_tapers == 5 and tmax == 0.2:
delta = 0.05
else:
delta = 0.004
assert_true(abs(signal_power_per_sample - mt_power_per_sample)
< delta)
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