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    %% Poles and Zeros of an Elliptic Lowpass Filter
% For data sampled at 1000 Hz, plot the poles and zeros of a 4th-order
% elliptic lowpass digital filter with cutoff frequency 200 Hz, 3 dB of
% ripple in the passband, and 30 dB of attenuation in the stopband.

% Copyright 2015 The MathWorks, Inc.


%%

[z,p,k] = ellip(4,3,30,200/500);
zplane(z,p)
grid
title('4th-Order Elliptic Lowpass Digital Filter')

%%
% Create the same filter using |designfilt|. Use |fvtool| to plot its poles
% and zeros.

d = designfilt('lowpassiir','FilterOrder',4,'PassbandFrequency',200, ...
               'PassbandRipple',3,'StopbandAttenuation',30, ...
               'DesignMethod','ellip','SampleRate',1000);
zplane(d)