Round function with multiple inputs not working in MATLAB function block in Simulink

Hi all,

I want to round a number to 3 decimal places. In MATLAB I can easily do it in this way:

>> number=25.0001;
>> round(25.0001,3)

 ans =

    25

If I try to do this in Simulink in a MATLAB Function block in this way:

 function D_avg1 = fcn(m)
 %#codegen

 D_avg1 = round(m,3);

It gives error:

 Error calling 'round'. This call-site passes more inputs to this function than it can accept.
Function 'BSD_System /Averaging/MATLAB Function' (#278.45.55), line 4, column 10:
"round(m,3)"
Launch diagnostic report.
Component: MATLAB Function | Category: Coder error

How to solve this?

Answer 1

[Azzi Abdelmalek]

Instead of round(u,3) use

round(u*1000)/1000

[Ahmed Hafsi]

It helped !! Very efficient ! Thanks !

[Erwin Mooij]

Any insight as to why it does not work? round(u,3) is a perfectly fine Matlab syntax. Is it because at the moment of initialising the model, Simulink does not now anything about the input "u" yet? I noticed in other situations as well that all data inside the embedded Matlab function should be known at the moment of initialisation.

[Paul]

Only the single argument syntax is supported:

https://www.mathworks.com/help/matlab/ref/round.html

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Code generation supports only the syntax Y = round(X).
• Code generation does not support char or logical data types for X.

[Paul]

I should have mentioned that if you want the 2-argument version declaring round as an extrinsic function should work.