Pole zero plot and frequancy response of a system in MATLAB

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Muhammad Ali
Muhammad Ali on 29 Oct 2020
Commented: Ameer Hamza on 30 Oct 2020
I have the following system:
I am required to find its frequency response using freqresp() function and find its magnitude response over the range 0 ≤ ω ≤ 20 in steps of 0.01. I am also required to plot its magnitude response and compare the results with its pole zero plot. I wrote following code for this in matlab but don't know whats the problem with this. The code is running without error but I think the plot of magnitude respnse is wrong. Kindly help me about these questions.
w = 0:0.01:20;
num = [3 4];
den = [1 5 8 4];
zeros = roots(num);
poles = roots(den);
H = tf (num,den);
%pzmap(H)
%grid on
H1 = freqresp(H,w);
H2 = squeeze(H1);
plot(w,abs(H2))
xlabel('w');
ylabel('freq response');

Answers (2)

Ameer Hamza
Ameer Hamza on 29 Oct 2020
It looks strange because the frequency response is usually plotted on logarithmic axes. Replace the line
plot(w,abs(H2))
with
loglog(w,abs(H2))
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Muhammad Ali
Muhammad Ali on 30 Oct 2020
Yeah thats correct now. Thank you for your kind help.

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