fitctree is not supported for code generation

I have fitctree function defined in my library. Why can't I generate a C code for this?? Require your valuable suggestions please!!!

[OCDER]

Likely your fitctree function uses a function that cannot be converted to C code. Take a look here and see if a matlab function that you used is NOT on the list. If there is an error message, post the full error message and upload your fitctree code (if okay for public viewing) so we can pinpoint the error.

https://www.mathworks.com/help/simulink/ug/functions-supported-for-code-generation-alphabetical-list.html