How do I exit a loop with a key hit?

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Harry
Harry on 1 Jul 2013
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.

Answers (4)

Lukas
Lukas on 22 Jan 2020
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
  1 Comment
Sanders A.
Sanders A. on 5 Feb 2020
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!!

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Vugar
Vugar on 30 Sep 2018

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

Jan
Jan on 1 Jul 2013
Edited: Jan on 1 Jul 2013
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
  8 Comments
Christopher Bitikofer
Christopher Bitikofer on 23 Dec 2022
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.

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Dulip Madurasinghe
Dulip Madurasinghe on 4 Dec 2018
This works. Thank you.

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