allow scalar IO in linearize

Author: baggepinnen

src/systems/abstractsystem.jl

@@ -1285,12 +1285,14 @@ The `simplified_sys` has undergone [`structural_simplify`](@ref) and had any occ
 See also [`linearize`](@ref) which provides a higher-level interface.
 """
 function linearization_function(sys::AbstractSystem, inputs,
-        outputs; simplify = false,
-        initialize = true,
-        op = Dict(),
-        p = DiffEqBase.NullParameters(),
-        zero_dummy_der = false,
-        kwargs...)
+    outputs; simplify = false,
+    initialize = true,
+    op = Dict(),
+    p = DiffEqBase.NullParameters(),
+    zero_dummy_der = false,
+    kwargs...)
+    inputs isa AbstractVector || (inputs = [inputs])
+    outputs isa AbstractVector || (outputs = [outputs])
     ssys, diff_idxs, alge_idxs, input_idxs = io_preprocessing(sys, inputs, outputs;
         simplify,
         kwargs...)
@@ -1584,7 +1586,7 @@ lsys_sym, _ = ModelingToolkit.linearize_symbolic(cl, [f.u], [p.x])
 ```
 """
 function linearize(sys, lin_fun; t = 0.0, op = Dict(), allow_input_derivatives = false,
-        p = DiffEqBase.NullParameters())
+    p = DiffEqBase.NullParameters(), kwargs...)
     x0 = merge(defaults(sys), op)
     u0, p2, _ = get_u0_p(sys, x0, p; use_union = false, tofloat = true)
 

test/linearize.jl

@@ -26,6 +26,13 @@ lsys, ssys = linearize(sys, [r], [r])
 @test lsys.C[] == 0
 @test lsys.D[] == 1
 
+lsys, ssys = linearize(sys, r, r) # Test allow scalars
+
+@test lsys.A[] == -2
+@test lsys.B[] == 1
+@test lsys.C[] == 0
+@test lsys.D[] == 1
+
 ##
 ```