def __pow__(self, other):
if not is_integer(other):
return NotImplemented
n, d = self.tf
if other > 0:
return LinearSystem(normalize(n**other, d**other), self.analog)
elif other < 0:
return LinearSystem(normalize(d**-other, n**-other), self.analog)
else:
assert other == 0
return LinearSystem(1., self.analog)
def __pow__(self, other):
if not is_integer(other):
return NotImplemented
n, d = self.tf
if other > 0:
return LinearSystem(normalize(n**other, d**other), self.analog)
elif other < 0:
return LinearSystem(normalize(d**-other, n**-other), self.analog)
else:
assert other == 0
return LinearSystem(1., self.analog)
def sys_equal(sys1, sys2, rtol=1e-05, atol=1e-08):
"""Returns true iff sys1 and sys2 have the same transfer functions."""
# TODO: doesn't do pole-zero cancellation
sys1 = LinearSystem(sys1)
sys2 = LinearSystem(sys2)
if sys1.analog != sys2.analog:
raise ValueError("Cannot compare analog with digital system")
tf1 = normalize(*sys2tf(sys1))
tf2 = normalize(*sys2tf(sys2))
for t1, t2 in zip(tf1, tf2):
if len(t1) != len(t2) or not np.allclose(t1, t2, rtol=rtol, atol=atol):
return False
return True
def sys_equal(sys1, sys2, rtol=1e-05, atol=1e-08):
"""Returns true iff sys1 and sys2 have the same transfer functions."""
# TODO: doesn't do pole-zero cancellation
sys1 = LinearSystem(sys1)
sys2 = LinearSystem(sys2)
if sys1.analog != sys2.analog:
raise ValueError("Cannot compare analog with digital system")
tf1 = normalize(*sys2tf(sys1))
tf2 = normalize(*sys2tf(sys2))
for t1, t2 in zip(tf1, tf2):
if len(t1) != len(t2) or not np.allclose(t1, t2, rtol=rtol, atol=atol):
return False
return True
def pink(N, state=None):
"""
Pink noise.
:param N: Amount of samples.
:param state: State of PRNG.
:type state: :class:`np.random.RandomState`
Pink noise has equal power in bands that are proportionally wide.
Power density decreases with 3 dB per octave.
"""
# This method uses the filter with the following coefficients.
#b = np.array([0.049922035, -0.095993537, 0.050612699, -0.004408786])
#a = np.array([1, -2.494956002, 2.017265875, -0.522189400])
#return lfilter(B, A, np.random.randn(N))
# Another way would be using the FFT
#x = np.random.randn(N)
#X = rfft(x) / N
state = np.random.RandomState() if state is None else state
uneven = N % 2
X = state.randn(N // 2 + 1 +
uneven) + 1j * state.randn(N // 2 + 1 + uneven)
S = np.sqrt(np.arange(len(X)) + 1.) # +1 to avoid divide by zero
y = (irfft(X / S)).real
if uneven:
y = y[:-1]
return normalize(y, 1)
def __add__(self, other):
self._check_other(other)
n1, d1 = self.tf
n2, d2 = LinearSystem(other, self.analog).tf
if len(d1) == len(d2) and np.allclose(d1, d2):
# short-cut to avoid needing pole-zero cancellation
return LinearSystem((n1 + n2, d1), self.analog)
return LinearSystem(normalize(n1*d2 + n2*d1, d1*d2), self.analog)
def __add__(self, other):
self._check_other(other)
n1, d1 = self.tf
n2, d2 = LinearSystem(other, self.analog).tf
if len(d1) == len(d2) and np.allclose(d1, d2):
# short-cut to avoid needing pole-zero cancellation
return LinearSystem((n1 + n2, d1), self.analog)
return LinearSystem(normalize(n1*d2 + n2*d1, d1*d2), self.analog)
def test_allclose(self):
"""Test for false positive on allclose in normalize() in
filter_design.py"""
# Test to make sure the allclose call within signal.normalize does not
# choose false positives. Then check against a known output from MATLAB
# to make sure the fix doesn't break anything.
# These are the coefficients returned from
# `[b,a] = cheby1(8, 0.5, 0.048)'
# in MATLAB. There are at least 15 significant figures in each
# coefficient, so it makes sense to test for errors on the order of
# 1e-13 (this can always be relaxed if different platforms have
# different rounding errors)
b_matlab = np.array([
2.150733144728282e-11, 1.720586515782626e-10,
6.022052805239190e-10, 1.204410561047838e-09,
1.505513201309798e-09, 1.204410561047838e-09,
6.022052805239190e-10, 1.720586515782626e-10, 2.150733144728282e-11
])
a_matlab = np.array([
1.000000000000000e+00, -7.782402035027959e+00,
2.654354569747454e+01, -5.182182531666387e+01,
6.334127355102684e+01, -4.963358186631157e+01,
2.434862182949389e+01, -6.836925348604676e+00,
8.412934944449140e-01
])
# This is the input to signal.normalize after passing through the
# equivalent steps in signal.iirfilter as was done for MATLAB
b_norm_in = np.array([
1.5543135865293012e-06, 1.2434508692234413e-05,
4.3520780422820447e-05, 8.7041560845640893e-05,
1.0880195105705122e-04, 8.7041560845640975e-05,
4.3520780422820447e-05, 1.2434508692234413e-05,
1.5543135865293012e-06
])
a_norm_in = np.array([
7.2269025909127173e+04, -5.6242661430467968e+05,
1.9182761917308895e+06, -3.7451128364682454e+06,
4.5776121393762771e+06, -3.5869706138592605e+06,
1.7596511818472347e+06, -4.9409793515707983e+05,
6.0799461347219651e+04
])
b_output, a_output = normalize(b_norm_in, a_norm_in)
# The test on b works for decimal=14 but the one for a does not. For
# the sake of consistency, both of these are decimal=13. If something
# breaks on another platform, it is probably fine to relax this lower.
assert_array_almost_equal(b_matlab, b_output, decimal=13)
assert_array_almost_equal(a_matlab, a_output, decimal=13)
def violet(N, state=None):
"""
Violet noise. Power increases with 6 dB per octave.
:param N: Amount of samples.
:param state: State of PRNG.
:type state: :class:`np.random.RandomState`
Power increases with +9 dB per octave.
Power density increases with +6 dB per octave.
"""
state = np.random.RandomState() if state is None else state
uneven = N % 2
X = state.randn(N // 2 + 1 +
uneven) + 1j * state.randn(N // 2 + 1 + uneven)
S = (np.arange(len(X))) # Filter
y = (irfft(X * S)).real
if uneven:
y = y[:-1]
return normalize(y, 1)
def test_allclose(self):
"""Test for false positive on allclose in normalize() in
filter_design.py"""
# Test to make sure the allclose call within signal.normalize does not
# choose false positives. Then check against a known output from MATLAB
# to make sure the fix doesn't break anything.
# These are the coefficients returned from
# `[b,a] = cheby1(8, 0.5, 0.048)'
# in MATLAB. There are at least 15 significant figures in each
# coefficient, so it makes sense to test for errors on the order of
# 1e-13 (this can always be relaxed if different platforms have
# different rounding errors)
b_matlab = np.array([2.150733144728282e-11, 1.720586515782626e-10,
6.022052805239190e-10, 1.204410561047838e-09,
1.505513201309798e-09, 1.204410561047838e-09,
6.022052805239190e-10, 1.720586515782626e-10,
2.150733144728282e-11])
a_matlab = np.array([1.000000000000000e+00, -7.782402035027959e+00,
2.654354569747454e+01, -5.182182531666387e+01,
6.334127355102684e+01, -4.963358186631157e+01,
2.434862182949389e+01, -6.836925348604676e+00,
8.412934944449140e-01])
# This is the input to signal.normalize after passing through the
# equivalent steps in signal.iirfilter as was done for MATLAB
b_norm_in = np.array([1.5543135865293012e-06, 1.2434508692234413e-05,
4.3520780422820447e-05, 8.7041560845640893e-05,
1.0880195105705122e-04, 8.7041560845640975e-05,
4.3520780422820447e-05, 1.2434508692234413e-05,
1.5543135865293012e-06])
a_norm_in = np.array([7.2269025909127173e+04, -5.6242661430467968e+05,
1.9182761917308895e+06, -3.7451128364682454e+06,
4.5776121393762771e+06, -3.5869706138592605e+06,
1.7596511818472347e+06, -4.9409793515707983e+05,
6.0799461347219651e+04])
b_output, a_output = normalize(b_norm_in, a_norm_in)
# The test on b works for decimal=14 but the one for a does not. For
# the sake of consistency, both of these are decimal=13. If something
# breaks on another platform, it is probably fine to relax this lower.
assert_array_almost_equal(b_matlab, b_output, decimal=13)
assert_array_almost_equal(a_matlab, a_output, decimal=13)
def _override_tf(b, a):
b, a = signal.normalize(b, a)
Rs_, Rct_, Cdl_ = tf_to_circuit(b, a)
b, a = circuit_to_tf((Rs if Rs else Rs_), (Rct if Rct else Rct_),
(Cdl if Cdl else Cdl_))
return b, a
def tf_to_circuit(b, a):
b, a = signal.normalize(b, a)
Rs = b[0]
Rct = (b[1] / a[1]) - Rs
Cdl = (a[1] * Rct)**-1
return (Rs, Rct, Cdl)
def tf(self):
b_hi, a_hi = self.tf_high
b_lo, a_lo = self.tf_low
b = polymul(b_hi, b_lo)
a = polymul(a_hi, a_lo)
return normalize(b, a)
def __hash__(self):
num, den = normalize(*self.tf)
return hash((tuple(num), tuple(den), self.analog))
def __mul__(self, other):
self._check_other(other)
n1, d1 = self.tf
n2, d2 = LinearSystem(other, self.analog).tf
return LinearSystem(normalize(n1*n2, d1*d2), self.analog)
def __hash__(self):
num, den = normalize(*self.tf)
return hash((tuple(num), tuple(den), self.analog))
def __mul__(self, other):
self._check_other(other)
n1, d1 = self.tf
n2, d2 = LinearSystem(other, self.analog).tf
return LinearSystem(normalize(n1*n2, d1*d2), self.analog)
