only adjust phase for rational systems

Author: baggepinnen

lib/ControlSystemsBase/src/plotting.jl

@@ -329,7 +329,7 @@ end
                 end
                 plotphase || continue
 
-                if adjust_phase_start == true
+                if adjust_phase_start == true && isrational(sbal)
                     intexcess = integrator_excess(sbal)
                     if intexcess != 0
                         # Snap phase so that it starts at -90*intexcess

lib/ControlSystemsBase/src/types/Lti.jl

@@ -1,4 +1,5 @@
 abstract type LTISystem{TE<:TimeEvolution} <: AbstractSystem end
+isrational(sys::LTISystem) = false
 +(sys1::LTISystem, sys2::LTISystem) = +(promote(sys1, sys2)...)
 -(sys1::LTISystem, sys2::LTISystem) = -(promote(sys1, sys2)...)
 function *(sys1::LTISystem, sys2::LTISystem)

lib/ControlSystemsBase/src/types/StateSpace.jl

@@ -234,6 +234,7 @@ function isstable(sys::StateSpace{<:Discrete, <:ForwardDiff.Dual})
     all(abs.(ForwardDiff.value.(sys.A)) .< 1)
 end
 
+isrational(::AbstractStateSpace) = true
 
 #####################################################################
 ##                         Math Operators                          ##

lib/ControlSystemsBase/src/types/TransferFunction.jl

@@ -98,6 +98,8 @@ function isproper(G::TransferFunction)
     return all(isproper(f) for f in G.matrix)
 end
 
+isrational(::TransferFunction) = true
+
 #####################################################################
 ##                         Math Operators                          ##
 #####################################################################