# Round Tripping Error

**URL:** <https://discourse.pumas.ai/t/round-tripping-error/666>\
**Category:** Estimation\
**Created:** [April 9, 2022, 3:16am UTC](https://discourse.pumas.ai/t/round-tripping-error/666 "2022-04-09T03:16:00Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![Rahulub3r](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/rahulub3r/32/182_2.png) [@Rahulub3r](https://discourse.pumas.ai/u/Rahulub3r)\
**Post date:** [April 9, 2022, 3:16am UTC](https://discourse.pumas.ai/t/round-tripping-error/666/1 "2022-04-09T03:16:01Z")

</div>

Hi I am trying to perform some re-fitting using a basic simulation and receiving an error. I would like to know how to resolve this. Thanks!

> **Code :**
>
> ```auto
> # Create subjects - dosing regimen + covariates
> dose = DosageRegimen(100, time = 0)
> choose_covariates() = (wt = rand(55:80), dose = 100)
> subj_with_covariates = map(1:10) do i
> Subject(id = i,
> events = dose,
> covariates = choose_covariates(),
> observations = (conc = nothing,))
> end
> 
> # Create model
> FOabs = @model begin
> @param begin
> tvcl ∈ RealDomain(lower=0)
> tvvc ∈ RealDomain(lower=0)
> tvka ∈ RealDomain(lower=0)
> Ω ∈ PDiagDomain(3) 
> σ_prop ∈ RealDomain(lower=0)
> end
> 
> @random begin
> η ~ MvNormal(Ω)
> end
> 
> @covariates wt
> 
> @pre begin
> CL = tvcl*(wt/70)^0.75*exp(η[1])
> Vc = tvvc*(wt/70)*exp(η[2])
> Ka = tvka*exp(η[3])
> end
> 
> @dynamics Depots1Central1
> 
> @derived begin
> conc = @. Central/Vc
> dv ~ @. Normal(conc, abs(conc) * σ_prop)
> end
> end
> 
> # Model parameters for simulation
> param = (tvcl = 5, tvvc = 20, tvka = 1,
> Ω = Diagonal([0.04, 0.04, 0.04]),
> σ_prop = 0.1)
> 
> # Perform simulations         
> sims = simobs(FOabs, subj_with_covariates, param, obstimes = 0:.1:24)
> 
> # Convert simulations to a population 
> pop = Subject.(sims)
> 
> # Re-fit
> refit_1cmp = fit(FOabs, pop, param, Pumas.FOCE())
> 
> ```

> **Error :**
>
> ```auto
> ERROR: LoadError: ArgumentError: Distribution is current not supported for the Pumas.FOCE() approximation. Please consider a different likelihood approximation.
> Stacktrace:
> [1] _∂²l∂η²(dv_d::Vector{Float64}, obsdv::Vector{ForwardDiff.Dual{ForwardDiff.Tag{Pumas.var"#407#408"{PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}, NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Float64, Float64, Float64, PDMats.PDiagMat{Float64, Vector{Float64}}, Float64}}, NamedTuple{(:obstimes,), Tuple{Nothing}}}, Float64}, Float64, 3}}, approx::Pumas.FOCE)
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:1915
> [2] (::Pumas.var"#415#419"{Pumas.FOCE})(::Tuple{Vector{Float64}, Vector{ForwardDiff.Dual{ForwardDiff.Tag{Pumas.var"#407#408"{PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}, NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Float64, Float64, Float64, PDMats.PDiagMat{Float64, Vector{Float64}}, Float64}}, NamedTuple{(:obstimes,), Tuple{Nothing}}}, Float64}, Float64, 3}}})
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:1692
> [3] map
> @ ./tuple.jl:213 [inlined]
> [4] map(::Function, ::NamedTuple{(:conc,), Tuple{Tuple{Vector{Float64}, Vector{ForwardDiff.Dual{ForwardDiff.Tag{Pumas.var"#407#408"{PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}, NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Float64, Float64, Float64, PDMats.PDiagMat{Float64, Vector{Float64}}, Float64}}, NamedTuple{(:obstimes,), Tuple{Nothing}}}, Float64}, Float64, 3}}}}})
> @ Base ./namedtuple.jl:197
> [5] _∂²l∂η²(m::PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, subject::Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}, param::NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Float64, Float64, Float64, PDMats.PDiagMat{Float64, Vector{Float64}}, Float64}}, vrandeffsorth::Vector{Float64}, approx::Pumas.FOCE, diffeq_options::NamedTuple{(), Tuple{}})
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:1692
> [6] (::Pumas.var"#_fgh!#337"{PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}, NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Float64, Float64, Float64, PDMats.PDiagMat{Float64, Vector{Float64}}, Float64}}, Pumas.FOCE, NamedTuple{(), Tuple{}}, TransformVariables.TransformTuple{NamedTuple{(:η,), Tuple{Pumas.MvNormalTransform{ZeroMeanDiagNormal{Tuple{Base.OneTo{Int64}}}}}}}, ParamSet{NamedTuple{(:η,), Tuple{ZeroMeanDiagNormal{Tuple{Base.OneTo{Int64}}}}}}})(F::Float64, G::Vector{Float64}, H::Matrix{Float64}, x::Vector{Float64})
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:463
> [7] (::NLSolversBase.var"#98#104"{NLSolversBase.InplaceObjective{Nothing, Nothing, Pumas.var"#_fgh!#337"{PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}, NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Float64, Float64, Float64, PDMats.PDiagMat{Float64, Vector{Float64}}, Float64}}, Pumas.FOCE, NamedTuple{(), Tuple{}}, TransformVariables.TransformTuple{NamedTuple{(:η,), Tuple{Pumas.MvNormalTransform{ZeroMeanDiagNormal{Tuple{Base.OneTo{Int64}}}}}}}, ParamSet{NamedTuple{(:η,), Tuple{ZeroMeanDiagNormal{Tuple{Base.OneTo{Int64}}}}}}}, Nothing, Nothing}, Float64})(G::Vector{Float64}, H::Matrix{Float64}, x::Vector{Float64})
> @ NLSolversBase /builds/PumasAI/PumasSystemImages-jl/.julia/packages/NLSolversBase/geyh3/src/objective_types/incomplete.jl:115
> [8] value_gradient_hessian!!(obj::NLSolversBase.TwiceDifferentiable{Float64, Vector{Float64}, Matrix{Float64}, Vector{Float64}}, x::Vector{Float64})
> @ NLSolversBase /builds/PumasAI/PumasSystemImages-jl/.julia/packages/NLSolversBase/geyh3/src/objective_types/incomplete.jl:138
> [9] initial_state(method::Optim.NewtonTrustRegion{Float64}, options::Optim.Options{Float64, Nothing}, d::NLSolversBase.TwiceDifferentiable{Float64, Vector{Float64}, Matrix{Float64}, Vector{Float64}}, initial_x::Vector{Float64})
> @ Optim /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Optim/uwNqi/src/multivariate/solvers/second_order/newton_trust_region.jl:306
> [10] optimize
> @ /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Optim/uwNqi/src/multivariate/optimize/optimize.jl:35 [inlined]
> [11] _orth_empirical_bayes!(vrandeffsorth::Vector{Float64}, m::PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, subject::Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}, param::NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Float64, Float64, Float64, PDMats.PDiagMat{Float64, Vector{Float64}}, Float64}}, approx::Pumas.FOCE, diffeq_options::NamedTuple{(), Tuple{}})
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:487
> [12] _update_ebes_and_evaluate_marginal_nll!
> @ /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:2054 [inlined]
> [13] _update_ebes_and_evaluate_marginal_nll_threads!(m::PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, population::Vector{Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}}, param::NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Float64, Float64, Float64, PDMats.PDiagMat{Float64, Vector{Float64}}, Float64}}, vvrandeffs::Vector{Vector{Float64}}, vvrandeffs_tmp::Vector{Vector{Float64}}, approx::Pumas.FOCE, diffeq_options::NamedTuple{(), Tuple{}})
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:2109
> [14] #440
> @ /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:2497 [inlined]
> [15] (::NLSolversBase.var"#69#70"{NLSolversBase.InplaceObjective{Nothing, Pumas.var"#440#445"{PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, Vector{Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}}, Pumas.FOCE, EnsembleThreads, NamedTuple{(), Tuple{}}, TransformVariables.TransformTuple{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{TransformVariables.ShiftedExp{true, Int64}, TransformVariables.ShiftedExp{true, Int64}, TransformVariables.ShiftedExp{true, Int64}, Pumas.PDiagTransform, TransformVariables.ShiftedExp{true, Int64}}}}, Vector{Vector{Float64}}, Vector{Vector{Float64}}}, Nothing, Nothing, Nothing}, Float64})(G::Vector{Float64}, x::Vector{Float64})
> @ NLSolversBase /builds/PumasAI/PumasSystemImages-jl/.julia/packages/NLSolversBase/geyh3/src/objective_types/incomplete.jl:54
> [16] value_gradient!!(obj::NLSolversBase.OnceDifferentiable{Float64, Vector{Float64}, Vector{Float64}}, x::Vector{Float64})
> @ NLSolversBase /builds/PumasAI/PumasSystemImages-jl/.julia/packages/NLSolversBase/geyh3/src/interface.jl:82
> [17] initial_state(method::Optim.BFGS{LineSearches.InitialStatic{Float64}, LineSearches.BackTracking{Float64, Int64}, Nothing, Float64, Optim.Flat}, options::Optim.Options{Float64, Pumas.var"#425#427"{Pumas.DefaultOptimizeFN{Nothing, NamedTuple{(:show_trace, :store_trace, :extended_trace, :g_tol, :allow_f_increases), Tuple{Bool, Bool, Bool, Float64, Bool}}}, Pumas.var"#441#446"{Pumas.FOCE, Bool, NLSolversBase.OnceDifferentiable{Float64, Vector{Float64}, Vector{Float64}}, TransformVariables.TransformTuple{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{TransformVariables.ShiftedExp{true, Int64}, TransformVariables.ShiftedExp{true, Int64}, TransformVariables.ShiftedExp{true, Int64}, Pumas.PDiagTransform, TransformVariables.ShiftedExp{true, Int64}}}}}}}, d::NLSolversBase.OnceDifferentiable{Float64, Vector{Float64}, Vector{Float64}}, initial_x::Vector{Float64})
> @ Optim /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Optim/uwNqi/src/multivariate/solvers/first_order/bfgs.jl:85
> [18] optimize
> @ /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Optim/uwNqi/src/multivariate/optimize/optimize.jl:35 [inlined]
> [19] (::Pumas.DefaultOptimizeFN{Nothing, NamedTuple{(:show_trace, :store_trace, :extended_trace, :g_tol, :allow_f_increases), Tuple{Bool, Bool, Bool, Float64, Bool}}})(cost::NLSolversBase.OnceDifferentiable{Float64, Vector{Float64}, Vector{Float64}}, p::Vector{Float64}, callback::Pumas.var"#441#446"{Pumas.FOCE, Bool, NLSolversBase.OnceDifferentiable{Float64, Vector{Float64}, Vector{Float64}}, TransformVariables.TransformTuple{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{TransformVariables.ShiftedExp{true, Int64}, TransformVariables.ShiftedExp{true, Int64}, TransformVariables.ShiftedExp{true, Int64}, Pumas.PDiagTransform, TransformVariables.ShiftedExp{true, Int64}}}}})
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:1973
> [20] _fit(m::PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, population::Vector{Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}}, param::NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Int64, Int64, Int64, Diagonal{Float64, Vector{Float64}}, Float64}}, approx::Pumas.FOCE, ensemblealg::EnsembleThreads, optimize_fn::Pumas.DefaultOptimizeFN{Nothing, NamedTuple{(:show_trace, :store_trace, :extended_trace, :g_tol, :allow_f_increases), Tuple{Bool, Bool, Bool, Float64, Bool}}}, fixedparamset::ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, fixedparam::NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Int64, Int64, Int64, Diagonal{Float64, Vector{Float64}}, Float64}}, checkidentification::Bool, diffeq_options::NamedTuple{(), Tuple{}})
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:2548
> [21] fit(m::PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, population::Vector{Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}}, param::NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Int64, Int64, Int64, Diagonal{Float64, Vector{Float64}}, Float64}}, approx::Pumas.FOCE; optimize_fn::Pumas.DefaultOptimizeFN{Nothing, NamedTuple{(:show_trace, :store_trace, :extended_trace, :g_tol, :allow_f_increases), Tuple{Bool, Bool, Bool, Float64, Bool}}}, constantcoef::NamedTuple{(), Tuple{}}, omegas::Tuple{}, ensemblealg::EnsembleThreads, checkidentification::Bool, diffeq_options::NamedTuple{(), Tuple{}})
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:2409
> [22] fit(m::PumasModel{ParamSet{NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}, PDiagDomain{PDMats.PDiagMat{Float64, Vector{Float64}}}, RealDomain{Int64, TransformVariables.Infinity{true}, Int64}}}}, var"#571#585", var"#572#586", var"#574#588", var"#576#590", Depots1Central1, var"#577#591", var"#581#595", Nothing}, population::Vector{Subject{NamedTuple{(:conc,), Tuple{Vector{Float64}}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}}}, param::NamedTuple{(:tvcl, :tvvc, :tvka, :Ω, :σ_prop), Tuple{Int64, Int64, Int64, Diagonal{Float64, Vector{Float64}}, Float64}}, approx::Pumas.FOCE)
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/estimation/likelihoods.jl:2392
> [23] top-level scope
> @ ~/data/code/WCOP_2022/WCOP_Day3.jl:468
> in expression starting at /home/jrun/data/code/WCOP_2022/WCOP_Day3.jl:468
> 
> ```

---

<div class="post-metadata">

**Author:** ![vijay](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/vijay/32/96_2.png) [@vijay](https://discourse.pumas.ai/u/vijay)\
**Post date:** [April 9, 2022, 10:10am UTC](https://discourse.pumas.ai/t/round-tripping-error/666/2 "2022-04-09T10:10:46Z")

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Use `:=` for your `conc` in the `@derived`

Since you are using the`Subject` constructor to generate the `Population` from the `SimulatedObservations`, all outputs from the derived block are being considered as `observations`. And you can only fit a distribution and not an expression (conc)

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**Author:** ![Rahulub3r](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/rahulub3r/32/182_2.png) [@Rahulub3r](https://discourse.pumas.ai/u/Rahulub3r)\
**Post date:** [April 9, 2022, 10:47am UTC](https://discourse.pumas.ai/t/round-tripping-error/666/3 "2022-04-09T10:47:40Z")

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Hi @vijay - this time I am getting an error at `pop = Subject.(sims)` itself. I tried passing `observations = [:dv]` but seems like we do not have that option for the `Subject` constructor

> **Error :**
>
> ```auto
> julia> pop = Subject.(sims)
> ERROR: type NamedTuple has no field conc
> Stacktrace:
> [1] getindex
> @ ./namedtuple.jl:118 [inlined]
> [2] (::Pumas.var"#165#166"{Pumas.SimulatedObservations{Subject{NamedTuple{(:conc,), Tuple{Nothing}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, Nothing}, StepRange{Int64, Int64}, NamedTuple{(:dv,), Tuple{Vector{Float64}}}}})(k::Symbol)
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/models/simulated_observations.jl:74
> [3] map
> @ ./tuple.jl:213 [inlined]
> [4] Subject(simsubject::Pumas.SimulatedObservations{Subject{NamedTuple{(:conc,), Tuple{Nothing}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, Nothing}, StepRange{Int64, Int64}, NamedTuple{(:dv,), Tuple{Vector{Float64}}}})
> @ Pumas /builds/PumasAI/PumasSystemImages-jl/.julia/packages/Pumas/HDuXQ/src/models/simulated_observations.jl:72
> [5] _broadcast_getindex_evalf
> @ ./broadcast.jl:648 [inlined]
> [6] _broadcast_getindex
> @ ./broadcast.jl:621 [inlined]
> [7] getindex
> @ ./broadcast.jl:575 [inlined]
> [8] copy
> @ ./broadcast.jl:922 [inlined]
> [9] materialize(bc::Base.Broadcast.Broadcasted{Base.Broadcast.DefaultArrayStyle{1}, Nothing, Type{Subject}, Tuple{Vector{Pumas.SimulatedObservations{Subject{NamedTuple{(:conc,), Tuple{Nothing}}, Pumas.ConstantCovar{NamedTuple{(:wt, :dose), Tuple{Int64, Int64}}}, Vector{Pumas.Event{Float64, Float64, Float64, Float64, Float64, Float64, Int64}}, Nothing}, StepRange{Int64, Int64}, NamedTuple{(:dv,), Tuple{Vector{Float64}}}}}}})
> @ Base.Broadcast ./broadcast.jl:883
> [10] top-level scope
> @ REPL[19]:1
> 
> ```

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<div class="post-metadata">

**Author:** ![vijay](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/vijay/32/96_2.png) [@vijay](https://discourse.pumas.ai/u/vijay)\
**Post date:** [April 9, 2022, 11:49am UTC](https://discourse.pumas.ai/t/round-tripping-error/666/4 "2022-04-09T11:49:04Z")

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@Rahulub3r the issue is that you specified the `observations` as `conc` in the creation of the `Population`. So, when using the `Subject` constructor, the specified `observation` takes precedence over the what you want to really `fit`. So, if you change `observations = conc` to `observations = dv` while creating the population, you should be good.

Also, I noticed that you are trying to re-fit a simulation where your simulation starts at time=0. I am 100% sure that the `re-fit` will give you a `Inf` loglikelihood because there is a zero concentration at the time of dosing. In these kind of scenarios, it is always best to start the simulation `obstimes` after dosing explicitly to not run into errors. So, e,g, 0.1:0.1:24

Hope that helps.

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<div class="post-metadata">

**Author:** ![Rahulub3r](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.pumas.ai/rahulub3r/32/182_2.png) [@Rahulub3r](https://discourse.pumas.ai/u/Rahulub3r)\
**Post date:** [April 9, 2022, 12:17pm UTC](https://discourse.pumas.ai/t/round-tripping-error/666/5 "2022-04-09T12:17:27Z")

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That solves it. Thanks @vijay !