 Predefined functions
 G (gaussian)
 GG (gaussian + gaussian)
 E (exponential)
 EE (exponential + exponential)
 Px (x degree polynomial)
 sin, cos, tan
 e, exp, log
 pi
 .createFunctionFromScript()
 +, , *, / and ** are supported.
 .createFunctionByName()
 Any function cataloged by the user can be used.
