scipy.signal.buttord¶
- scipy.signal.buttord(wp, ws, gpass, gstop, analog=0)[source]¶
Butterworth filter order selection.
Return the order of the lowest order digital Butterworth filter that loses no more than gpass dB in the passband and has at least gstop dB attenuation in the stopband.
Parameters : wp, ws : float
Passband and stopband edge frequencies, normalized from 0 to 1 (1 corresponds to pi radians / sample). For example:
- Lowpass: wp = 0.2, ws = 0.3
- Highpass: wp = 0.3, ws = 0.2
- Bandpass: wp = [0.2, 0.5], ws = [0.1, 0.6]
- Bandstop: wp = [0.1, 0.6], ws = [0.2, 0.5]
gpass : float
The maximum loss in the passband (dB).
gstop : float
The minimum attenuation in the stopband (dB).
analog : int, optional
Non-zero to design an analog filter (in this case wp and ws are in radians / second).
Returns : ord : int
The lowest order for a Butterworth filter which meets specs.
wn : ndarray or float
The Butterworth natural frequency (i.e. the “3dB frequency”). Should be used with butter to give filter results.
