How to pass variables to a callback function and back again?

Hello, I have a callback function that is executed every so often. What I wish to do is pass a matrix and an integer (e.g. x = []; y = 1;) to the callback, have them manipulated and then outputted to the parent program.

x = [];
y = 1;
t = timer('TimerFcn',@imagecap,'ExecutionMode','fixedRate','Period',0.3333, 'UserData', x, y);
start(t)
if epoch == 31
    stop(t)
end 

%--------------
function [x, y] = imagecap(obj, event, arg1, arg2)

I've looked at the matlab help but that section seems rather obtuse.

[Fangjun Jiang]

I want to know it too!

Answer 1

[Paulo Silva]

The timer code, TimerFcn is executed in the base workspace so the reason for the assignin lines (just in case you use the code inside a function and not in scripts)

%These are the initial values of your variables
assignin('base','x',100)
assignin('base','y',200)
t = timer('TimerFcn','[x, y] = imagecap(x, y)',...
'ExecutionMode','fixedRate','Period',0.3333);
start(t)

Example TimerFcn, just increments the x and y values

function [x,y]=imagecap(x,y)
x=x+1;
y=y+1;
disp(x)
disp(y)
end

Always remember to do delete(timerfindall) so you don't have timer objects using memory after you use them.

[Fangjun Jiang]

Here you go! That's the answer. Just put in the return arguments in the callback of the timer object.