only simplify small systems automatically

Project.toml

@@ -1,7 +1,7 @@
 name = "SymbolicControlSystems"
 uuid = "886cb795-8fd3-4b11-92f6-8071e46f71c5"
 authors = ["Fredrik Bagge Carlson"]
-version = "0.1.1"
+version = "0.1.2"
 
 [deps]
 ControlSystems = "a6e380b2-a6ca-5380-bf3e-84a91bcd477e"

src/SymbolicControlSystems.jl

@@ -37,10 +37,15 @@ end
 
 function SymPy.Sym(sys::StateSpace{<:Any,Sym})
     A, B, C, D = ControlSystems.ssdata(sys)
-    if isdiscrete(sys)
-        (C*inv(z * I(size(A, 1)) - A)*B+D)[1]
+    expr = if isdiscrete(sys)
+        (C*inv(z * I(size(A, 1)) - A)*B+D)
+    else
+        (C*inv(s * I(size(A, 1)) - A)*B+D)
+    end
+    if size(expr) == (1,1)
+        return expr[]
     else
-        (C*inv(s * I(size(A, 1)) - A)*B+D)[1]
+        return expr
     end
 end
 
@@ -56,7 +61,11 @@ function Num(sys::StateSpace{<:Any,Num})
     A, B, C, D = ControlSystems.ssdata(sys)
     λ = isdiscrete(sys) ? Symb.@variables(z) : Symb.@variables(s)
     λ = λ[]
-    Symb.simplify((C*inv(λ * I(size(A, 1)) - A)*B+D)[1])
+    ex = (C*inv(λ * I(size(A, 1)) - A)*B+D)[1]
+    if sys.nx < 4
+        ex = Symb.simplify(ex)
+    end
+    ex
 end
 
 function Num(sys::TransferFunction)
@@ -120,6 +129,12 @@ function ControlSystems.minreal(sys::StateSpace{<:Any,NumOrDiv})
     nsys = Symb.simplify_fractions.(nsys)
 end
 
+function ControlSystems.minreal(sys::StateSpace{<:Any,Sym})
+    # sys |> Symb.Num .|> Symb.symbolics_to_sympy .|> sp.simplify
+    nsys = Sym(sys)
+    nsys = sp.simplify.(nsys)
+end
+
 function Num(x::Sym)
     try
         return Float64(x)