{"id":5589,"date":"2014-10-24T09:47:23","date_gmt":"2014-10-24T13:47:23","guid":{"rendered":"https:\/\/blogs.mathworks.com\/pick\/?p=5589"},"modified":"2014-10-24T09:47:23","modified_gmt":"2014-10-24T13:47:23","slug":"stop","status":"publish","type":"post","link":"https:\/\/blogs.mathworks.com\/pick\/2014\/10\/24\/stop\/","title":{"rendered":"STOP!"},"content":{"rendered":"
\r\n \r\n

Sean<\/a>'s pick this week is Display progress, pause or stop a time-consuming loop<\/a> by Rafael Oliveira<\/a>.\r\n <\/p>\r\n <\/introduction>\r\n

Background<\/a><\/h3>\r\n

It is not uncommon to see questions such asking \"How do I stop a for<\/tt> or while<\/tt> loop when a user pushes a button?\"<\/a> in MATLAB Answers<\/a>. There are a few ways to do this, but usually the results involve checking the state of a toggle button or some flag that\r\n has been set by a user. Alternatively, one could consider replacing the for<\/tt> or while<\/tt> loop with a timer<\/tt> which is what I typically recommend.\r\n <\/p>\r\n

Rafael's stop<\/tt> makes stopping a loop easy and elegant to do.\r\n <\/p>

for<\/span> ii = 1:100\r\n    if<\/span> ~stop.requested\r\n        disp(['Still Running, iteration: '<\/span> num2str(ii)])\r\n\r\n        % Computationally expensive operation.<\/span>\r\n        fft2(rand(5000));\r\n    else<\/span>\r\n        % I clicked said stop<\/span>\r\n        disp('Stopped'<\/span>)\r\n        break<\/span>\r\n    end<\/span>\r\n    drawnow\r\nend<\/span><\/pre>
Still Running, iteration: 1\r\nStill Running, iteration: 2\r\nStill Running, iteration: 3\r\nStill Running, iteration: 4\r\nStill Running, iteration: 5\r\nStill Running, iteration: 6\r\nStill Running, iteration: 7\r\nStopped\r\n<\/pre> 
This utility also allows you to pause and resume elegantly.<\/p>\r\n   
How I found it?<\/a><\/h3>\r\n   
I typically find File Exchange submissions either by randomly browsing, needing some piece of functionality, or trying to\r\n      help someone not reinvent the wheel.  However, I came by this one a little differently. Out of curiosity, I wanted to know\r\n      which File Exchange submissions contain the string \"xkcd\".  This one came up with a nice little easter egg related to a specific comic<\/a>.\r\n   <\/p>\r\n   
Turning that mode on:<\/p>
for<\/span> ii = 0:0.3:1\r\n    stop.setStatus('xkcd'<\/span>,ii)\r\n    drawnow\r\n    snapnow\r\nend<\/span><\/pre>    
Comments<\/a><\/h3>\r\n   
What approaches do you usually take to allow for user interactions with a loop or timer?<\/p>\r\n   
Give it a try and let us know what you think here<\/a> or leave a comment<\/a> for Rafael.\r\n   <\/p>