Plot two figures on the same figure using subplot

Question

I am trying to plot the following using subplot how can I do that? Thank you

[n,wc]= buttord(Wp,Ws,Rp,Rs);  
[z,p,k]=butter(n,wc);
sos = zp2sos(z,p,k);   


freqz(sos) ;
grpdelay(sos) ;

Note that this is non-trivial since freqz yields a subplot already.

You should have been more elaborate with your question, without [this comment](http://stackoverflow.com/questions/27374467/plot-two-figures-on-the-same-figure-using-subplot#comment43200085_27374898) clarifying on [`freqz`](http://ch.mathworks.com/help/signal/ref/freqz.html#bt8l89o-1) creating a subplot this question seemed trivial. — Tobias Kienzler, Dec 09 '14 at 09:11
@TobiasKienzler - I agree that this is no longer a duplicate. I will vote to reopen. The OP should have explicitly stated that `subplot` did not work out of the box. — rayryeng, Dec 12 '14 at 17:11

Lord Henry Wotton · Accepted Answer · 2014-12-09T09:46:08.923

The following would work if the functions you are using plotted one figure each: call subplot right before each function that produces a graphic output. It is kind of straightforward from the manual, subplot(m,n,p) splits the figure into a grid of m x n graphics and draws the p-th one. However, as pointed by @hbaderts, freqz produces a subplot of its own, so you would need to rearrange it to include the upcoming output of grpdelay.

This is how you could do it, as per the workaround proposed in this thread (see it for the more general solution).

freqz(sos);
h = get(gcf, 'children');
fig2=figure;
figure(fig2)
g=subplot(3,1,1)
set(h(1), 'pos', get(g, 'pos'))
figure(fig2)
g=subplot(3,1,2)
set(h(2), 'pos', get(g, 'pos'))
close
g=subplot(3,1,3)
grpdelay(sos)

As `freqz` plots magnitude and phase in subplots, this does not work. — hbaderts, Dec 09 '14 at 09:05

score 2 · Answer 2 · answered Dec 09 '14 at 09:24

Probably the easiest solution is calculating the frequency response with freqz and plotting it with freqzplot. This is not the best solution because freqzplot is obsolete. A better solution would be to manually create the plots (e.g. 20*log10(abs(h))).

[h,w] = freqz(sos);
subplot(2,2,1);
freqzplot(h,w,'mag');
subplot(2,2,3);
freqzplot(h,w,'phase');
subplot(2,2,[2,4]);
grpdelay(sos);

Plot two figures on the same figure using subplot

2 Answers2