Interpreted Matlab function error

Hello all,

I'm building a Simulink model in which I have to implement some differential equations. I created a matlab function which takes some inputs and performs the needed operations. My syntaxe is:

function dx=test(x)
%%some variables
...
%%equations
dx1 = ...
dx2 = ...
...
dx11 = ...

dx=[dx1;dx2;dx3;dx4;dx5;dx6;dx7;dx8;dx9;dx10;dx11];
end

However, when running it in Simulink, it returns me the error: Evaluation of expression resulted in an invalid output. Only finite double vector or matrix outputs are supported.

The really weird part is: when I go to Matlab's Command Window and:

1) Run the exact same code lines: It works and I receive dx as a vector of eleven finite values, exactly as expected.

2) Call the function by its name, passing the correct inputs: I receive ans = [] and the variable dx is not even declared;

Does anyone have an idea of what might possibly be the cause?

Thank you in advance.

[Ameer Hamza]

If possible, attach the actual function to the question. I will be easy to spot the issue. Otherwise, you can use MATLAB debugging options to spot the problem inside the function https://www.mathworks.com/help/matlab/matlab_prog/debugging-process-and-features.html.

[Stephen23]

"Does anyone have an idea of what might possibly be the cause?"

Possibly a bug in the code, or how it is being called. But without the code we cannot say much more than this. If you want help with this, please upload the function by clicking the paperclip button.

[Pedro Seger]

Hello all,

I found out that the problem was that I was calling some global variables that apparently weren't being recognized by the function itself.

Since all my equations depended on them, nothing was calculed. However, it escapes me how the global variables were not found by the function, given that they were explicitly defined by other code.

Thank you for your attention!

[Guillaume]

However, it escapes me how the global variables were not found by the function

That's one of the many reasons why global variables are to be avoided like the plague. It's very difficult to keep track of their state which leads to subtle and very hard to debug behaviour.

[Stephen23]

Once again globals cause problems that are hard to debug. So no surprises there.

@Pedro Seger: avoid using global variables (this is the best advice you will get on them). There are much better (neater, faster, easier to debug) ways of passing data between workspaces, e.g. parameterized functions or nested functions. See:

https://www.mathworks.com/help/matlab/matlab_prog/share-data-between-workspaces.html

[Ting Liang]

Hi Stephen,

Excuse me.

I encountered the same problem now, I tried your methods, but it didn't work, could you please give some clues? Thanks. The problems are described as follows:

In simulink, I used the interpreted MATLAB function, to call for HEX_LT function, it works.

But if there is a subfunction (like SFHC) within the HEX_LT function, shown as follows:

function y = HEX_LT(para)

hex = SHFC (Pa_in, Ga, Qw, di, Tb);

Uo = 1/(1/ho + do^2 /(hex(i)* di^2));

... y = T;

end

I have tried several ways, but all didn't work, all told me that ' Evaluation of expression resulted in an invalid output. Only finite double vector or matrix outputs are supported', could you please help with this?

Thanks, and looking forward to your reply.