Pole zero plot and frequancy response of a system in MATLAB

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');

Answer 1

[Ameer Hamza]

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))

[Muhammad Ali]

Now I am getting this.

But how would know that this plot correct? and whats the of this plot with pole zero plot?

[Ameer Hamza]

You can use bode() function to see if this is correct.

Answer 2

[Muhammad Ali]

Yeah thats correct now. Thank you for your kind help.

[Ameer Hamza]

I am glad to be of help!!!