How to observe the result of an unbounded array in simulink?

Hello there, I am a new user of both simulink and matlab. I am doing some experiment for my capstone project, but I encountered an exception in simulink where I created a matlab function and want to observed the results. The matlab function should return some matrices but when I clicked "Run", the compiler throws an exception like this:

A signal of unbounded array type is not supported on 'Input Port 3' of block 'test_simulink_model/Scope'. For a list of supported data types, see the block documentation page.

However, I dont understand why is this happening and how to solve this. Could I have your advice?

[madhan ravi]

Show the MATLAB Function code

[S.Lau]

Hi, thanks for your reply. I am playing around with the code like this:

function result = test_function(frequency, fft_points)

result = 0:frequency/fft_points:((frequency/2)-(frequency/fft_points));

end

This will throws the exception as I described. Should I use something elses in the simulink if I want to observe the result?

Answer 1

[Fangjun Jiang]

Depending on the value of frequency and fft_points, the length of "result" could vary dramatically, thus "unbounded".

In Simulink, the size of most variables is fixed, like always 5 or always [3,4]. There could be variable size data but the maximum size has to be specified. For example, specify the max size of "result" as 100. During simulation running, the actual size of "result" could be 50 or 60, as long as it is <=100.

https://www.mathworks.com/support/search.html/answers/654813-how-do-i-resolve-an-error-about-variable-sized-data-in-my-matlab-function-block.html

[madhan ravi]

+1, @fangjun did you mean to link something else?, you have linked this thread in the answer.

[Fangjun Jiang]

Thank you, @madhan ravi! That was a typo. The link is now updated to point to a Q&A by the Mathworks Support Team.

[madhan ravi]

:)

[S.Lau]

Thank you for the advice! It did solve one of the problem of my test model.