You may declare that a DEFINITION name represents a complex quantity. The format of a complex declaration is:
name = COMPLEX ( real_name , imaginary_name )
This declaration tells FlexPDE that name represents a complex quantity, and assigns the real_name and imaginary_name to the real and imaginary parts of name. You can perform arithmetic operations or request graphical output of either the name itself, or its components individually.
Cr = 5
Ci = 7
C = COMPLEX(Cr,Ci)