Using timer, How can I cleanly exit a function execution, when the timer fires in MATLAB?

My problem is that I can't find a Function to callback as a 'TimerFcn', that cleanly exits my function without errors.

t = timer('StartDelay',2,'TimerFcn', );

Thanks in advance.

[Guillaume]

Can you explain more clearly what you're trying to do exactly, particularly, the order of execution of the various things you want to happen.

[taima zoabi]

For Example::

function [i] = Example()

t = timer('ExecutionMode','singleShot','StartDelay',2,'TimerFcn',...

@(~,~)Command_that_exits_the_Function);

start(t)

for i=1:1000

i=i+1;

disp(i)

end

end

In this case scenario what can I use as ''Command_that_exits_the_Function'', works for me too if you have some other way to stop and exit my function when the timer fires, other than using the a callback function as 'TimerFcn'.

thank you.

Answer 1

[Walter Roberson]

There are only four ways in MATLAB to force a function to stop executing without its cooperation:

1. quit MATLAB
2. force an out-of-memory error
3. force an infinite recursion
4. Use jave robot or similar to simulate pressing control-C in the command line (note: this might not terminate immediately

There is no way to send a signal to a particular function to force that one function to stop, and there is no way to send a signal to a particular function to force that one function to error().

Therefore what you should do is write your timer to set a flag in an area that the other code checks periodically.

http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functions_in_my_GUI.28s.29.3F

[taima zoabi]

thank you.

[Sean de Wolski]

@Walter, You can also cancel(parfeval Future). Quit and exit aren't fool proof and can pop up a dialog if there's an unsaved file in the editor. Killing the jvm with java.lang.System.exit(0) works reliably.

[Walter Roberson]

Quiting the jvm won't work if you started with -nojvm …

[Walter Roberson]

I just tried in R2020b, and found that MATLAB:pmaxsize (too much memory) and MATLAB:lang:StackOverflow (too many levels of recursion) can both be caught. However, it would be worth testing out what happens when the problem is triggered in a callback that is not really part of the code being executed.

Answer 2

[Sean de Wolski]

Why use a timer for this?

In the start of your function, start a tic

t = tic

Then periodically check

if toc(t)>2
    return 
end

[taima zoabi]

Thank you, but I need it to exit exactly after a certain amount of time.

I didn't want to complicate things before, But what I am realy trying to do is to display images in a figure window for 30 seconds, where the image displayed changes when the user pushes the button. And after the 30 seconds are over, I want the function to exit.

So my code is:

%%%
function [] = StartTask3(Task3Time,Task3_IMG,No_of_images)
%Manual
            Images_order = randperm(No_of_images);
           
            t = timer('ExecutionMode','singleShot','StartDelay',30,'TimerFcn',...
                @(~,~)Command_that_exits_the_Function);
            start(t)

            for i=1:40
                image(eval(['Task3_IMGS.im' num2str(Images_order(i)) ';' ]));
                set(gca, 'XTick', [], 'YTick', []);
                
                w = waitforbuttonpress;
            end
            
            
end
%%%