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import numpy as np
from scipy import linalg
from numpy.testing import assert_almost_equal, assert_array_almost_equal
from nose.tools import assert_true
from mne.time_frequency.stft import stft, istft, stftfreq, stft_norm2
def test_stft():
"Test stft and istft tight frame property"
sfreq = 1000. # Hz
f = 7. # Hz
for T in [253, 256]: # try with even and odd numbers
t = np.arange(T).astype(np.float)
x = np.sin(2 * np.pi * f * t / sfreq)
x = np.array([x, x + 1.])
wsize = 128
tstep = 4
X = stft(x, wsize, tstep)
xp = istft(X, tstep, Tx=T)
freqs = stftfreq(wsize, sfreq=1000)
max_freq = freqs[np.argmax(np.sum(np.abs(X[0]) ** 2, axis=1))]
assert_true(X.shape[1] == len(freqs))
assert_true(np.all(freqs >= 0.))
assert_true(np.abs(max_freq - f) < 1.)
assert_array_almost_equal(x, xp, decimal=6)
# norm conservation thanks to tight frame property
assert_almost_equal(np.sqrt(stft_norm2(X)),
[linalg.norm(xx) for xx in x], decimal=2)
# Try with empty array
x = np.zeros((0, T))
X = stft(x, wsize, tstep)
xp = istft(X, tstep, T)
assert_true(xp.shape == x.shape)
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