MATLAB: I have a syntax error with Fcn

Question

I want to give a formula is sign(u(2)-u(3)) into Fcn, but I got a message is

The expression: sign(u(2)-u(3))

in 'hebonnuoc/He bon nuoc /h1dot'

has a syntax error

Answer 1

The documentation page shows that you should use sgn instead of sign: https://www.mathworks.com/help/simulink/ref_obsolete_blocks/fcn.html

sgn(u(2)-u(3))

Also, this block is obsolete; consider using a better alternative: https://www.mathworks.com/help/simulink/slref/matlabfunction.html