How to Loop Subplots with Updated Outputs in Matlab? - matlab

Question

I want to create a frontend where the user can browse pictures forward by pressing Enter.
Pseudo-Code
hFig=figure
nFrames=5;
k=1;
while k < nFrames
u=signal(1*k,100*k,'data.wav'); % 100 length
subplot(2,2,1);
plot(u);
subplot(2,2,2);
plot(sin(u));
subplot(2,2,3);
plot(cos(u));
subplot(2,2,4);
plot(tan(u));
% not necessary but for heading of overal figure
fprintf('Press Enter for next slice\n');
str=sprintf('Slice %d', k);
mtit(hFig, str);
k=k+1;
keyboard
end
function u=signal(a,b,file)
[fs,smplrt]=audioread(file);
u=fs(a:b,1);
end
where
something is wrong in updating the data because pressing CMD+Enter increases k by one but does not update the data. Sometimes (rarely), the data is once the next iteration.
something is wrong with while's condition because k can be bigger than nFrames. keyboard just keep asking for more inputs.
My mistake earlier in Error-Checking
I had earlier a problem where the closure of the window lead to the crash of the application. I include this here because I mentioned a problem about it in the comment of one answer. I avoid the problem now by
hFig=figure;
n=5;
k=1;
while k<nFrames
% for the case, the user closes the window but starts new iteration
if(not(ishandle(hFig)))
hFig=figure;
end
...
end
which creates a new Figure if the earlier was closed by the user.
I tried unsuccessfully putting hFig=figure; inside the while loop's if clause earlier to avoid repetition in the code.
Please, let me know if you know why you cannot have the handle hFig in the while loop's if clause.
How can you loop subplots with updated outputs in Matlab?

Answer 1

To stop the script waiting for an input from the user you should use input instead of keyboard.
Actually keyboard makes your script entering in a debug mode. It stops the executino of the script as (like a breakpoint) allowing the user to, for example, check the value of a variable.
You can modify your scripr as follows (modification are at the end of your script, identified by "UPDATED SECTION):
hFig=figure
nFrames=5;
k=1;
while k < nFrames
u=signal(1*k,100*k,'handel.wav'); % 100 length
subplot(2,2,1);
plot(u);
subplot(2,2,2);
plot(sin(u));
subplot(2,2,3);
plot(cos(u));
subplot(2,2,4);
plot(tan(u));
% not necessary but for heading of overal figure
%
% UPDATED SECTION
%
% Use the string "Press Enter for next slice\n" as the prompt for the
% call to "input"
%
% fprintf('Press Enter for next slice\n');
% str=sprintf('Slice %f', k);
% Use %d instead of "%f" to print integer data
str=sprintf('Slice %d', k);
mtit(hFig, str);
k=k+1;
% Use "input" instead of "keyboard"
% keyboard
input('Press Enter for next slice\n')
end
Hope this helps.
Qapla'