If you have not explicitly set a domain, FX Graph will choose one for you.
Cartesian and inverse graphs have a domain implied by the size of the axes and FX Graph will automatically draw a graph for this implied domain.
Polar and parametric graphs have no implied domain so FX Graph uses:
Polar graphs 0 £ q £ 360 (degrees mode)
Parametric graphs 0 £ t £ 20
If your polar or parametric graph is incomplete, you may need to set your own domain.