Call MATLAB Function

[resono-mp3]

I was keen to try the new Call MATLAB Function node in LabVIEW 2021 and learned that if you make changes to the m-file, you must kill the MATLAB process before running the VI again.  

For example, put the attached VI and M-file in the same directory and run the VI.  We can see that B = 1 - A.  

Change line 3 of the M-file to B = 1 + A, and we still get 

But if we kill the MATLAB process 

and re-run the VI, we now have the expected behavior of B = 1 + A.  

 

Is this the intended behavior?  Either way I'm posting here so others know what to expect.   

[AeroSoul]

Did you restart the VI after the change was made or went straight for the kill?

[resono-mp3]

I just checked - closing the VI doesn't change this behavior. 

Quitting LabVIEW, however, has the same effect as killing the MATLAB process.

[cbutcher · Accepted solution]

It's a known issue, see https://www.ni.com/en-gb/support/documentation/bugs/21/labview-2021-known-issues.html

It claims it's resolved in LabVIEW 2022. Not sure what to make of that...

[aartjan]

I have built an executable in LV2022Q3 calling an m file. But after closing the reference, the matlab process remains active. Only when I terminate the app, the matlab process terminates as well.

I ended up calling a second m file that kills the matlab process! Obviously an error is returned in Labview, but that can be simply ignored.

I also learned that if you get an error when calling a matlab function, chances are that you cannot rerun the routine without getting the same error over and over again. You will need to kill the matlab process first.

[aartjan]

kill script:

function exit_()

    feature getpid;

    cmd = ['!taskkill /F /PID ' num2str(ans)];

    eval(cmd)

end

[aartjan]

Shame btw that the call matlab function won't also accept string input.