Error when supplying default_u0: Dict(kv): kv needs to be an iterator of tuples or pairs

[baggepinnen]

The example below throws an exception when supplying default_u0 but not without

using ModelingToolkit, ControlSystems
using ControlSystems: ssdata, AbstractStateSpace, Continuous, nstates, noutputs, ninputs
import ModelingToolkit: ODESystem

function ODESystem(sys::AbstractStateSpace{Continuous}; name::Symbol)
    A,B,C,D = ssdata(sys)
    nx,ny,nu = nstates(sys), noutputs(sys), ninputs(sys)
    @parameters t
    @variables x[1:nx](t) y[1:ny](t) u[1:nu](t)
    Dₜ = Differential(t)
    eqs = [
        Dₜ.(x) .~ A*x .+ B*u
        y      .~ C*x .+ D*u
    ]
    ODESystem(eqs; name, default_u0 = zeros(nx)) # errors
    # ODESystem(eqs; name) # works
end

sys = ControlSystems.DemoSystems.resonant()
linearsys = ODESystem(sys; name=:Linearsys)

julia> linearsys = ODESystem(sys; name=:Linearsys)
ERROR: ArgumentError: Dict(kv): kv needs to be an iterator of tuples or pairs
Stacktrace:
 [1] Dict(kv::Vector{Float64})
   @ Base ./dict.jl:132
 [2] ODESystem(deqs::Vector{Equation}, iv::Sym{ModelingToolkit.Parameter{Real}, Nothing}, dvs::Vector{Any}, ps::OrderedCollections.OrderedSet{Any}; observed::Vector{Num}, systems::Vector{ODESystem}, name::Symbol, default_u0::Vector{Float64}, default_p::Dict{Any, Any})
   @ ModelingToolkit ~/.julia/packages/ModelingToolkit/DQzuf/src/systems/diffeqs/odesystem.jl:92
 [3] ODESystem(eqs::Vector{Equation}, iv::Nothing; kwargs::Base.Iterators.Pairs{Symbol, Any, Tuple{Symbol, Symbol}, NamedTuple{(:name, :default_u0), Tuple{Symbol, Vector{Float64}}}})
   @ ModelingToolkit ~/.julia/packages/ModelingToolkit/DQzuf/src/systems/diffeqs/odesystem.jl:174
 [4] ODESystem(sys::StateSpace{Continuous, Float64}; name::Symbol)
   @ Main ~/.julia/dev/ControlSystems/src/modelingtoolkit.jl:15
 [5] top-level scope
   @ REPL[35]:1

[anandijain]

can you try giving it a Pair[state1=>val1, ... ]?
Just zeros() won't work because in a more complicated example it's not obvious which u0 goes to which state.

[YingboMa]

Yes, this is expected. Try default_u0 = Dict(x .=> 0).

[baggepinnen]

Then perhaps the appropriate error is a method error that tells me there is not method that accepts an array? This sort of thing is rather important for usability.

[YingboMa]

Yes, will do.