DynamicSystems

Any ideas why the following is giving me an error message?  Maple 14 WinXP 32 bit

restart:

with(DynamicSystems):

sys:=TransferFunction((0.04798*z+0.0464)/(z^2-1.81*z+0.9048),discrete=true,sampletime=0.1);

PrintSystem(sys);

PhaseMargin(sys);
                                    Error, (in DynamicSystems:-PhaseMargin:-PhaseMargin) cannot split rhs for multiple assignment
 

I'm expecting a PM of   13.5711degrees.

View 221_PhaseMargin.mw on MapleNet or Download 221_PhaseMargin.mw

Regards,

Georgios