Set axis type for
rfplot in RF Toolbox
setrfplot( applies or
removes the use of engineering units on the X-axis of
By default, engineering units are always applied in the X-axis and persist
across all MATLAB sessions.
This example shows how to design a low-pass Butterworth filter with passband frequency of 3 kHz, stopband frequency 7 kHz, passband attenuation of 2 dB, and stopband attenuation 60 dB. Display the filter order of such a designed filter and determine the passband frequency at 3.0103 dB. See  in rffilter object page.
Fp = 3e3; % Passband frequency, Hz Ap = 2; % Passband attenuation, dB Fs = 7e3; % Stopband frequency, Hz As = 60; % Stopband attenuation, dB
r = rffilter("FilterType","Butterworth","ResponseType","Lowpass","Implementation","Transfer function","PassbandFrequency",Fp, ... "PassbandAttenuation",Ap,"StopbandFrequency",Fs,"StopbandAttenuation",As);
Filter order of the designed filter
N = r.DesignData.FilterOrder; sprintf('Calculated filter order is %d',N)
ans = 'Calculated filter order is 9'
Frequency at 3.0103 dB
F_3dB = r.DesignData.PassbandFrequency/1e3; sprintf('Frequency at 3.0103 dB is %d kHz',F_3dB)
ans = 'Frequency at 3.0103 dB is 3.090733e+00 kHz'
Visualize magnitude response
frequencies = linspace(0,2*Fs,1001); rfplot(r, frequencies)
Note: To use rfplot and plot on the same figure use
setplot. Type 'help setrfplot' in command window for information.
Larry D. Paarmann, Design and Analysis of Analog Filters: A Signal Processing Perspective, Kluwer Academic Publishers
axistype— Units on
rfplot X-axis, specified as
persist— Units on
rfplotX-axis across MATLAB sessions
rfplot X-axis across MATLAB sessions,