matlab update two set of subplots inside a loop

Question

I have two sets of subplots. I want to update them within a loop. For example,

 % first figure
 f1 = figure;
 f11 = subplot(1,2,1), plot(a1);
 f12 = subplot(1,2,1), plot(b1);


 % second figure
 f2 = figure;
 f21 = subplot(1,2,1), plot(a2);
 f22 = subplot(1,2,1), plot(b2);

 for i = 1:3
      calculate a1, b1;
      update subplots in f1;

      calculate a2, b2;
      update subplots in f2;
 end

How can I do it?

I don't understand what you're asking. You update them the same way you plotted them in the first place. — sco1, Jun 05 '15 at 13:42

score 3 · Answer 1 · edited May 23 '17 at 10:28

Get handles to the plot objects, update their 'YData' property, and then call drawnow to make sure the figure is refreshed. (An alternative would be to simply re-do the plot each time, but that probably is slower).

Note that in the following code I also change two subplot lines as commented by @SanthanSalai, and change variable i to n to avoid shadowing the imaginary unit.

%// first figure
f1 = figure;
f11 = subplot(1,2,1), h11 = plot(a1);
f12 = subplot(1,2,2), h12 = plot(b1);

%// second figure
f2 = figure;
f21 = subplot(1,2,1), h21 = plot(a2);
f22 = subplot(1,2,2), h22 = plot(b2);

for n = 1:3
    %// calculate a1, b1;
    set(h11, 'YData', a1);
    set(h12, 'YData', b1);

    %// calculate a2, b2;
    set(h21, 'YData', a2);
    set(h22, 'YData', b2);
end

score 2 · Accepted Answer · answered Aug 15 '16 at 09:26

As stated by Luis, subplots in a loop can be updated though the use of 'Ydata' after the plots have been predefined.

I was having a similar problem, and I just wanted to share an extended example.

% create two sets of data;
a1 = zeros(2,1)
b1 = zeros(2,1)
a2 = zeros(2,1)
b2 = zeros(2,1)

% first figure
f1 = figure;
f11 = subplot(1,2,1), h11 = plot(a1);
f12 = subplot(1,2,2), h12 = plot(b1);

% second figure
f2 = figure;
f21 = subplot(1,2,1), h21 = plot(a2);
f22 = subplot(1,2,2), h22 = plot(b2);

% apply a y limit, used only to enhance the plots
set(f11,'ylim',[-3 3])
set(f12,'ylim',[-3 3])
set(f21,'ylim',[-3 3])
set(f22,'ylim',[-3 3])

for n = 1:3

    % calulate a1 and b1
    a1(end) = a1(end)+1
    b1(end) = b1(end)-1

    set(h11, 'YData', a1);
    set(h12, 'YData', b1);

    % calculate a2, b2;
    a2 = -a1
    b2 = -b1

    set(h21, 'YData', a2);
    set(h22, 'YData', b2);

    pause(1)
end

matlab update two set of subplots inside a loop

2 Answers2