%% Frequency Response of a Butterworth Analog Filter
% Design a 9th-order Butterworth analog lowpass filter. Display its magnitude and phase responses.

[z,p,k] = buttap(9);          % Butterworth filter prototype
[num,den] = zp2tf(z,p,k);     % Convert to transfer function form
freqs(num,den)                % Frequency response of analog filter

% Copyright 2015 The MathWorks, Inc.