Change variables in the base workspace through a Matlab Function block

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Hi,
I'm trying to change a matrix (of type double) in the base workspace through a Matlab Function block in Simulink. To access the matrix in the base workspace within the Matlab function block, I have set the variable type in the Symbols pane of the Matlab function block to parameter data. Then I change the parameter and assign it to the base workspace with the assignin function, which I found in past solutions for the same problem.
Here is an example of my problem:
function updateBaseWorkspaceVariable(Workplan, TasksToDo)
% Modify the base workspace variable using the parameters
assignin('base', 'myVariable', Workplan + TasksToDo);
end
However when running my code and this example code I get the following error message:
Error:Function 'assignin' not supported for code generation.
Function 'MATLAB Function' (#343.124.176), line 3, column 5:
"assignin('base', 'myVariable', Workplan + TasksToDo)"
Launch diagnostic report.
Since this is a solution already used in past Matlab versions I'm wondering, if it's a problem within the Matlab version that I'm using (23a) or whether there is something I'm missing.
Thanks in advance for your help!
Kind regards
Lisa

Accepted Answer

Jon
Jon on 21 Sep 2023
Edited: Jon on 21 Sep 2023
I would suggest using the "Interpreted MATLAB Function" block for this purpose. It doesn't need to get compiled. It is under
Simulink>User-Defined Functions in the Library Browser.
In the Parameters field MATLAB function, enter something like myfun(u).
In a directory that is on the MATLAB path, make and save an .m file called myfun(u), that has your code it in it, e.g.
function y = myfun(u)
y = u^2;
assignin('base', 'y',y);
  5 Comments
Jon
Jon on 2 Oct 2023
Hi Lisa, if you are all set, please accept an answer so others will know that an answer is available. Thanks

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More Answers (1)

Harald
Harald on 21 Sep 2023
Hi Lisa,
you can declare a function as extrinsic to address the error message, using coder.extrinsic.
I would question the workflow of writing to the base workspace every time the block is executed. If you only need to have the variable in the workspace after the simulation, you can use model callbacks.
Best wishes,
Harald
  1 Comment
Lisa P
Lisa P on 22 Sep 2023
Hi Harald,
Thank you for your quick reply as well!
Also thank you for the tipp on model callbacks. I might use those in other places. For my question the writing to the base workspace at every time of the blocks execution was intended. I'm using the table in the workspace as an input for a state chart. I want the table to be updated at certain discrete points in time to symbolise tasks being added to a To-Do-List. Then there is a state in the state chart that checks whether there are tasks in the list and when there are tasks the state 'working' is reached. Otherwise the state 'waiting' remains active. Therefore I wanted the list to be updated at every timestep.
My solution might not be the best, but I was just trying to make an idea work (:
Kind regards,
Lisa

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