So the block you are experiencing is not reading the fantastic manual?

i have errors here

You're problem is a MATLAB error, not VHDL.

If the left is your MATLAB code, try to declare `yl` in the form `f = 
@(arglist)expression` 
(https://www.tutorialspoint.com/matlab/matlab_functions.htm)

I meant `y1`

yes i  try to convert my code matlab on vhdl

But the Error is in the Matlab code. First write working correct Matlab 
code. If you did this, then you can generate VHDL. But first fix the 
Errors in the Matlab code.
As stated in the Error message, there is no y1 defined in your code but 
you use it.