How do I exit a loop with a key hit?

So I have a loop in my code but I want to exit the loop and move onto the next set of calculations after I hit some key. I know that I could ask for input in the loop, which could confirm whether I could move on or not but that would require me to confirm at each loop which I don't want to be doing.

Answer 1

[Lukas]

In a similar way I use wait bat cancel button:

hWaitbar = waitbar(0, 'Iteration 1', 'Name', 'Solving problem','CreateCancelBtn','delete(gcbf)');
for i=1:5
    % Some long taking computation
    pause(5);
    % Check
    drawnow;
    if ~ishandle(hWaitbar)
        % Stop the if cancel button was pressed
        disp('Stopped by user');
        break;
    else
        % Update the wait bar
        waitbar(i/5,hWaitbar, ['Iteration ' num2str(i)]);
    end
end

[Sanders A.]

I prefer this answer because it doesn't latch on to an existing figure and upon hitting the cancel/'stop now' button delete the figure. This si nice for being able to leave my figures in specific places on my screen and run&stop my animations as I please.

Thank you!!

[Lorenzo]

excellent! Thank you

Answer 2

[Vugar]

The answer of Jan is almost correct - only one code line is missing:

ButtonHandle = uicontrol('Style', 'PushButton', ...
                         'String', 'Stop loop', ...
                         'Callback', 'delete(gcbf)');
for k = 1:1e6
  disp(k)
  if ~ishandle(ButtonHandle)
    disp('Loop stopped by user');
    break;
  end
pause(0.01); % A NEW LINE
end

Answer 3

[Jan]

You can create a waitbar or any other GUI which contains a button for breaking the loop. Then check a property inside the loop and break is the value chnages. This property could be the existence of the figure or the button as well as the UserData of the button or figure.

ButtonHandle = uicontrol('Style', 'PushButton', ...
                         'String', 'Stop loop', ...
                         'Callback', 'delete(gcbf)');

for k = 1:1e6
  disp(k)
  if ~ishandle(ButtonHandle)
    disp('Loop stopped by user');
    break;
  end
end

[Tom]

I tried your code but when i run the script, the pushbotton never appears. The code runs and displays the k values, but the opportunity to press the pushbutton and then enter the if statement never occurs.

Only when i press cntrl + c does the pushbutton appear.

[Eyman FAKHRI]

Hello, have you find the solution for this problem ?

[Mickael Pruvost]

Hi, is anyone found why this code doesn't show the figure and the button to stop the loop?

[Phillip Warren]

I've discovered (in Matlab R2018b) that placing a pause(1) before the for loop allows for the figure to pop up. However, the button does not stop the loop.

[Rik]

You may need to call drawnow to force queued callbacks to be executed. The same would be true before the loop. The pause function implicitly calls drawnow.

[S. Gokhun Tanyer]

Did not work for version: 9.5.0.944444 (R2018b) :(

[Rik]

S. Gokhun Tanyer, what is the exact code you tried?

[Christopher Bitikofer]

clarifying point. the uicontrol function tries to draw on the current figure, When I didn't have one open it didn't instantiate its own figure. I setup the following code to initialize the uibutton on an independant figure.

breakLoopFigure = figure('color','w','Name','Plotter');

breakLoopFigure.Position = [1325 612 560 420];

breakLoopFigure.Visible = "on";

breakLoopFigure.Units = "normalized";

ButtonHandle = uicontrol(breakLoopFigure,...

'Style','pushbutton',...

'String', 'Stop loop', ...

'Callback', 'delete(gcbf)');

ButtonHandle.Units = "normalized";

ButtonHandle.Position = [.1 .1 .8 .8];

drawnow

This works quite well for my purpose, but you could just as easily place the button on an app gui or a plot with other data. Others have pointed out the waitbar also works well.

Answer 4

[Dulip Madurasinghe]

This works. Thank you.