def test_decim():
"""Test evoked decimation."""
rng = np.random.RandomState(0)
n_epochs, n_channels, n_times = 5, 10, 20
dec_1, dec_2 = 2, 3
decim = dec_1 * dec_2
sfreq = 1000.
sfreq_new = sfreq / decim
data = rng.randn(n_epochs, n_channels, n_times)
events = np.array([np.arange(n_epochs), [0] * n_epochs, [1] * n_epochs]).T
info = create_info(n_channels, sfreq, 'eeg')
info['lowpass'] = sfreq_new / float(decim)
epochs = EpochsArray(data, info, events)
data_epochs = epochs.copy().decimate(decim).get_data()
data_epochs_2 = epochs.copy().decimate(decim, offset=1).get_data()
data_epochs_3 = epochs.decimate(dec_1).decimate(dec_2).get_data()
assert_array_equal(data_epochs, data[:, :, ::decim])
assert_array_equal(data_epochs_2, data[:, :, 1::decim])
assert_array_equal(data_epochs, data_epochs_3)
# Now let's do it with some real data
raw = read_raw_fif(raw_fname, add_eeg_ref=False)
events = read_events(event_name)
sfreq_new = raw.info['sfreq'] / decim
raw.info['lowpass'] = sfreq_new / 4. # suppress aliasing warnings
picks = pick_types(raw.info, meg=True, eeg=True, exclude=())
epochs = Epochs(raw, events, 1, -0.2, 0.5, picks=picks, preload=True,
add_eeg_ref=False)
for offset in (0, 1):
ev_ep_decim = epochs.copy().decimate(decim, offset).average()
ev_decim = epochs.average().decimate(decim, offset)
expected_times = epochs.times[offset::decim]
assert_allclose(ev_decim.times, expected_times)
assert_allclose(ev_ep_decim.times, expected_times)
expected_data = epochs.get_data()[:, :, offset::decim].mean(axis=0)
assert_allclose(ev_decim.data, expected_data)
assert_allclose(ev_ep_decim.data, expected_data)
assert_equal(ev_decim.info['sfreq'], sfreq_new)
assert_array_equal(ev_decim.times, expected_times)
