How to run a Matlab script asynchronously from a Matlab app?

I currently have an app that has a button that is supposed to start and stop another matlab script. The other Matlab script is supposed to run until the button in the app is pushed again.

The app's logic looks roughly like this:

function StartDataCollectionButtonPushed(app, event)

% app.experiment_running is a public variable

if(app.experiment_running == false)

% Change state of app to indicate experiment is running

app.experiment_running = true;

app.StartDataCollectionButton.BackgroundColor = [1 0 0];

app.StartDataCollectionButton.Text = "Stop Data Collection";

% Placeholder value, assume this is a valid file path.

run("Matlab_File.m");

else

% Change state of app to indicate no experiment is running

app.experiment_running = false;

app.StartDataCollectionButton.BackgroundColor = [0 1 0];

app.StartDataCollectionButton.Text = "Start Data Collection";

% Need way of quitting Matlab_File.m

end

else

And the external Matlab_File.m looks like this:

z = 0;

while app.experiment_running

% This counter is here so that the script will eventually quit on its own if I cannot stop it

z = z+1

if z >= 1e5

return

end

end

The problem is that run("Matlab_File.m") is a blocking call, so even if I click on the "StartDataCollectionButton" as Matlab_File.m is executing, experiment_running isn't set to false until Matlab_File.m returns on its own. I'd like to be able to change that flag in the middle of Matlab_File's execution and have it exit the loop and return.

Answer 1

[Jon]

One way would be to use a MATLAB timer and make your script that you want to execute asynchonously be the timer's callback function. Note that if this script is to execute repeatedly you can set up the timer for periodic execution (rather than using a loop)

Please see this link for general info on setting up timers and timer functions: https://www.mathworks.com/help/matlab/matlab_prog/use-a-matlab-timer-object.html

Timers have a stop function that could be called when you push the button to stop the test.

If there is some cleanup that must be done when the timer stops you can also provide the timer with a stop callback function to perform those steps.

[Jon]

I think you could also use events and listeners for this, but I am not as familiar with this approach https://www.mathworks.com/help/matlab/matlab_oop/learning-to-use-events-and-listeners.html

[Jan Bartels]

Hi Jon, thanks for taking the time to answer the question! I appreciate it. I will look into both of these suggestions.

[Jon]

Let me know if you have questions when you get into the details

[Jan Bartels]

For posterity, I was able to do what I wanted with the following setup. In the app I have the following code:

function StartDataCollectionButtonPushed(app, event)

% app.experiment_running is a public variable

if(app.experiment_running == false)

% Change state of app to indicate experiment is running

app.experiment_running = true;

app.StartDataCollectionButton.BackgroundColor = [1 0 0];

app.StartDataCollectionButton.Text = "Stop Data Collection";

% This block uses a timer to run the Data

% Collection Script (DCS) asynchronously in the

% background.

s = strcat("run('","Matlab_File.m","')");

app.t = timer('TimerFcn','disp(''.'')','StartFcn',s,'StopFcn','','StartDelay',0);

% It then pushes a new variable called

% 'experimentRunning' into the base workspace that

% the DCS can access.

% The DCS needs to collect data while

% experimentRunning is true, and save data & return

% when 'experimentRunning' goes to 0.

assignin('base','experimentRunning',1);

% This line calls the 'StartFcn' function of the

% timer, which is declared as s a few lines above.

start(app.t);

else

% Change state of app to indicate no experiment is running

app.experiment_running = false;

app.StartDataCollectionButton.BackgroundColor = [0 1 0];

app.StartDataCollectionButton.Text = "Start Data Collection";

% Quit the Matlab script by setting 'experimentRunning' to

% 0. The expectation is that this will cause the script to

% quit collecting and store its data.

assignin('base','experimentRunning',0);

stop(app.t); % Stop and close the timer.

delete(app.t);

end

end

And the matlab script looks like this:

z = 0;

while experimentRunning

z = z + 1;

disp(z)

% Counter only used for development, to ensure script will eventually

% return if experimentRunning isn't being set correctly

if z >= 8e4

return

end

% This pause is necessary. Without it the script never updates experimentRunning

pause(0.0001)

end

% Add code to save data here

[Jon]

That's good, I'm glad you were able to get it working using the timer

Answer 2

[Bruno Luong]

@Jan Bartels "The problem is that run("Matlab_File.m") is a blocking call, so even if I click on the "StartDataCollectionButton" as Matlab_File.m is executing, experiment_running isn't set to false until Matlab_File.m returns on its own."

I have implemented the same pattern and I don't think it's true, Callback is even driven. You have to make sure the properties 'Interruptible' is set to 'on' and 'BusyAction' to 'queue'. When you click it will change, you might add 'redraw' statement at the end of the callback and before the check in your script so that the event is correctly broadcasted and arrived.

You might add some code to protect with user click twice and the script have some latency to capture the stop event or such.

[Jan Bartels]

I will have to look into this. Looking at the app, the button has been set to be interruptible and busy action has been set to queue.

Currently the behavior is that if I click the button while the blocking script is running it will wait to change the color until the script has finished. Clicking the button multiple times will cause the app to wait until the script has finished and then relaunch it so the queue behavior definitely seems to be there.

Maybe the issue has been that the script didn't have a pause statement. I will test this.

[Bruno Luong]

pause(x) will do a redraw

redraw is like pause with no waittime.