MATLAB: Plotting response of multiple filters in single figure of freqz/freqs and fvtool

MATLABmatlab functionplotplotting

https://www.mathworks.com/matlabcentral/answers/73580-how-to-plot-multiple-bode-plots-in-one-figure

The above link discusses about plotting multiple graphs(bode responses)in one figure

But how can we achieve this purpose in case of commands like freqz,freqs and fvtool?

Best Answer

This is likely the only option:

[h{1},w{1}] = freqz(rand(5,1),1, 2^16, 1000);
[h{2},w{2}] = freqz(rand(5,1),1, 2^16, 1000);
figure
subplot(2,1,1)
hold on
for k = 1:2
    plot(w{k},20*log10(abs(h{k})))
end
hold off
grid
subplot(2,1,2)
hold on
for k = 1:2
    plot(w{k},unwrap(angle(h{k})))
end
hold off
grid

Related Solutions

MATLAB: How to plot the result of multiple freqs functions in the same grid

I suspect the issue it looks different is because your axes are using a linear scale instead of a logarithmic. Try this.

first plot uses loglog. Removed 20*log10 from Y values. Replaced the axes command with xlim.
Second plot uses semilogx

%Filter Butterworth
[zb,pb,kb] = butter(3,1,'s');
[bb,ab] = zp2tf(zb,pb,kb);
[h{1},w{1}] = freqs(bb,ab,1000);
figure
freqs(bb,ab,1000);
%Filter  Chebyshev
[z1,p1,k1] = cheby1(3,1,1,'s');
[b1,a1] = zp2tf(z1,p1,k1);
[h{2},w{2}] = freqs(b1,a1,1000);
figure
freqs(b1,a1,1000);
%Filter  Eliptic
[ze,pe,ke] = ellip(3,1,30,1,'s');
[be,ae] = zp2tf(ze,pe,ke);
[h{3},w{3}] = freqs(be,ae,1000);
figure
freqs(be,ae,1000);
%Filter  Bessel
[zs,ps,ks] = besself(3,1);
[bs,as] = zp2tf(zs,ps,ks);
[h{4},w{4}] = freqs(bs,as,1000);
figure
freqs(bs,as,1000);
figure
subplot(2,1,1)
for k = 1:4
    loglog(w{k},abs(h{k}))
    hold on
end
hold off
grid
xlim([0.01 10]);
xlabel('Frequency (rad/s)');
ylabel('Attenuation (dB)');
legend('Butterworth','Chebyshev','Elliptik','Bessel','Location',"southwest");
subplot(2,1,2)
for k = 1:4
    semilogx(w{k},angle(h{k})*180/pi)
    hold on
end
hold off
grid
xlabel('Frequency (rad/s)');
ylabel('Phase');
legend('Butterworth','Chebyshev','Elliptik','Bessel','Location',"southwest");