Simulink running despite error message

So, I have the following issue, that confuses me. I have simulink model to compare different controller (in Variant Subsystems). I use mainly MATLAB Function Blocks to implement those controllers. For one controller, however, simulink throws me an error message:

This is the only error message and it doesn't make sense to me. But the simulation completes normally, and all the values seem correct. I could also set breakpoints and check on the matrix dimensions:

I am wondering if anybody had same issue and what causes it? I could just ignore it, but this does not seem right for me. I would rather fix this.

[Walter Roberson]

As a matter of form, I would avoid using

r_n = N_x(1)\r;

The \ is seldom used with scalar left operand, so most people will not understand the operation you are doing there, which is equivalent to

r_n = r ./ N_x(1);

[Marko Marković]

Ah, I see. Thank you for the remark!!

Answer 1

[halleyhit]

It seems Simulink can not determine the size of variables in MATLAB Function block. Please try to use "edit data" on top left, and set your intput and output variable size other than -1.

[Marko Marković]

Thank you very much!! This resolved the issue. Do you know what might be the root cause? I did not have such an issue ever and I heavily use Matlab Function Blocks.

[halleyhit]

With setting size to -1, sometimes MATLAB is able to detemine the size, but sometimes it can not. I have no idea on when the detemination works, but best practice is to set the value strongly.

[Marko Marković]

I see, thank you! I'll stick then with best practices and just set the dimensions.