hi

i am trying to write one compartment first order absorption model with lag time . i have a doubt on how to write lag time in model. here i am showing the model which i have written , this model worked but did not give the exact result. please review it once and suggest me the changed where it is needed

```
model = @model begin
@param begin
tvcl ∈ RealDomain(lower=0, init = 1.0)
tvv ∈ RealDomain(lower=0, init = 100)
tvka ∈ RealDomain(lower = 0, init= 0.5)
tvlag ∈ RealDomain(lower = 0, init = 0.5)
Ω ∈ PDiagDomain(init=[0.04])
σ ∈ RealDomain(lower=0,init=0.01)
end
@random begin
η ~ MvNormal(Ω)
end
@pre begin
CL = tvcl * exp(η[1])
V = tvv
ka = tvka
lag = tvlag
end
@dynamics begin
Depot' = - ka * Depot
Central' = ka * Depot - (CL/V) * Central
end
@vars begin
Depot = Depot
Cent = Central/V
end
@derived begin
cp = Cent
dv ~ @. Normal(cp, abs(cp)*σ)
end
end
```