def compute_parameters(self, target='stopband'):
""" This function computes the order and the -3 dB-frequency
of the filter for the specific parameters.
Arguments:
target: The optimization goal for the filter computation.
Choices are:
- stopband: optimize to the stopband (like MATLAB)
- passband: optimize to the passband
"""
if target not in ['passband', 'stopband', None]:
raise ValueError("Target must be one of passband or stopband, \
or not given if filter is not Butterworth.")
else:
self.filter_target = target
if True: # Change here to be more verbose.
print("Ws = ", self.Ws)
print("Wp = ", self.Wp)
print("Rp = ", self.passband_attenuation)
print("Rs = ", self.stopband_attenuation)
if self.filter_class == 'butterworth':
if target == 'passband':
self.N, self.Wn = signal.buttord(self.Wp, self.Ws,
self.passband_attenuation,
self.stopband_attenuation,
analog=True)
elif target == 'stopband':
self.N, self.Wn = custom.custom_buttord(self.Wp, self.Ws,
self.passband_attenuation,
self.stopband_attenuation,
analog=True)
else:
raise ValueError("Butterworth filters must match either the \
passband or the stopband.")
elif self.filter_class == 'chebyshev_1':
self.N, self.Wn = signal.cheb1ord(self.Wp, self.Ws,
self.passband_attenuation,
self.stopband_attenuation,
analog=True)
elif self.filter_class == 'chebyshev_2':
self.N, self.Wn = signal.cheb2ord(self.Wp, self.Ws,
self.passband_attenuation,
self.stopband_attenuation,
analog=True)
elif self.filter_class == 'elliptical':
self.N, self.Wn = signal.ellipord(self.Wp, self.Ws,
self.passband_attenuation,
self.stopband_attenuation,
analog=True)
else:
raise NotImplementedError(
"Filter family {} not yet implemented".format(self.filter_class))
pass
def _compute_parameters(self):
normalized_pb, normalized_sb = self.normalized_pb_sb()
self.already_normalized_Wn = True
if self.target == 'passband':
self.N, self.Wn = signal.buttord(normalized_pb, normalized_sb,
self.filter_parameters['passband_attenuation'],
self.filter_parameters['stopband_attenuation'],
analog=False)
elif self.target == 'stopband': # Match stopband (like MATLAB)
self.N, self.Wn = custom.custom_buttord(normalized_pb, normalized_sb,
self.filter_parameters['passband_attenuation'],
self.filter_parameters['stopband_attenuation'],
analog=False)
else:
raise ValueError("Butterworth filters must match or the passband\
or the stopband.")
