add identity named_ss method

Author: baggepinnen

Project.toml

@@ -1,7 +1,7 @@
 name = "RobustAndOptimalControl"
 uuid = "21fd56a4-db03-40ee-82ee-a87907bee541"
 authors = ["Fredrik Bagge Carlson", "Marcus Greiff"]
-version = "0.4.48"
+version = "0.4.49"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/named_systems2.jl

@@ -280,15 +280,12 @@ fb = feedback(s1, s2, r = :r) #
 """
 function named_ss(sys::AbstractStateSpace{T};
     x = :x,
-    u = :u, # sinze is used instead of sys.nu for ExtendedStateSpace
+    u = :u,
     y = :y,
     name::String = "",
     unique = true,
     extra = Dict{Symbol, Any}(),
     ) where T
-    if sys isa NamedStateSpace
-        error("Cannot wrap a named statespace in a named statespace")
-    end
     x = expand_symbol(x, sys.nx)
     u = expand_symbol(u, size(sys,2)) # size is used instead of sys.nu for ExtendedStateSpace
     y = expand_symbol(y, size(sys,1))
@@ -308,6 +305,17 @@ function named_ss(sys::AbstractStateSpace{T};
     NamedStateSpace{T, typeof(sys)}(sys, x, u, y, name, extra)
 end
 
+function named_ss(sys::NamedStateSpace{T};
+    x = sys.x,
+    u = sys.u,
+    y = sys.y,
+    name::String = sys.name,
+    unique = true,
+    extra = sys.extra,
+    ) where T
+    named_ss(sys.sys; x, u, y, name, unique, extra)
+end
+
 """
     named_ss(sys::AbstractStateSpace, name; x, y, u)
 

test/test_named_systems2.jl

@@ -25,6 +25,9 @@ s_autoname = named_ss(G1, :G)
 s3 = NamedStateSpace(ssdata(G1)..., s1.x, s1.u, s1.y)
 @test s3 == s1
 
+s32 = named_ss(s3)
+@test s32 == s3
+
 @test s1[:y, :u] == s1
 @test s1[[:y], [:u]] == s1