do not promote system type when creating a vector

Author: baggepinnen

lib/ControlSystemsBase/src/ControlSystemsBase.jl

@@ -237,7 +237,7 @@ function __init__()
             print(io, " for automatic discretization (applicable to systems without delays or nonlinearities only).")
         end
         plots_id = Base.PkgId(UUID("91a5bcdd-55d7-5caf-9e0b-520d859cae80"), "Plots")
-        if nameof(exc.f) === :plot && parentmodule(argtypes[1]) == @__MODULE__() && !haskey(Base.loaded_modules, plots_id)
+        if exc.f !== nothing && nameof(exc.f) === :plot && parentmodule(argtypes[1]) == @__MODULE__() && !haskey(Base.loaded_modules, plots_id)
             printstyled(io, "\nPlotting is not available unless Plots.jl is loaded manually. Call `using Plots` before plotting.", color=:green, bold=true)
         elseif (exc.f == /) && argtypes[2] <: DelayLtiSystem
             print(io, "A delayed system can not be inverted. Consider use of the function `feedback`.")

lib/ControlSystemsBase/src/connections.jl

@@ -138,6 +138,13 @@ end
 Base.typed_hcat(::Type{S}, X::Number...) where {S<:LTISystem} = hcat(convert.(S, X)...)
 Base.typed_hcat(::Type{S}, X::Union{AbstractArray{<:Number,1}, AbstractArray{<:Number,2}}...) where {S<:LTISystem} = hcat(convert.(S, X)...)
 
+## Mixed-type array creation
+# When creating an array of systems, an error may be thrown if the default Base.vect is called that tries to promote all systems to a common type. E.g., when using non-proper transfer functions and statespace systems. We thus opt out of the conversion with the method below
+function Base.vect(X::LTISystem...)
+    LTISystem[X...]
+end
+
+
 """
     add_input(sys::AbstractStateSpace, B2::AbstractArray, D2 = 0)
 

lib/ControlSystemsBase/src/types/conversion.jl

@@ -136,8 +136,8 @@ function siso_tf_to_ss(T::Type, f::SisoRational)
     num0, den0 = numvec(f), denvec(f)
     # Normalize the numerator and denominator to allow realization of transfer functions
     # that are proper, but not strictly proper
-    num = num0 / den0[1]
-    den = den0 / den0[1]
+    num = num0 ./ den0[1]
+    den = den0 ./ den0[1]
 
     N = length(den) - 1 # The order of the rational function f
 

lib/ControlSystemsBase/test/test_connections.jl

@@ -148,7 +148,11 @@ P = ss(-1.0, 2.0, 3.0, 4.0)
 @test [2.5 P 3.5] == ss(-1.0, [0.0 2.0 0.0], 3.0, [2.5 4.0 3.5])
 @test [2.5; P; 3.5] == ss(-1.0, 2.0, [0.0; 3.0; 0.0], [2.5; 4.0; 3.5])
 
-
+# Test vector creation
+v = [ssrand(1,1,1), tf(1)]
+@test v isa Vector{LTISystem}
+@test v[1] isa StateSpace{Continuous, Float64}
+@test v[2] isa TransferFunction{Continuous, ControlSystemsBase.SisoRational{Int64}}
 
 # Combination tfRational and sisoZpk
 Czpk_111 = zpk([-2],[-5],1)