How can I control what become new parameters in the ini() block during model modification?

[billdenney]

In the example below, I want f_study1 as a new parameter in the ini() block, but I don't want STUDYID as a new parameter. How can I control this? My current work-around is to make STUDYID <- 1 as part of the model and then remove it.

library(nlmixr2)
#> Warning: package 'nlmixr2' was built under R version 4.2.2
#> Loading required package: nlmixr2data

one.compartment <- function() {
  ini({
    tka <- 0.45
    tcl <- 1
    tv <- 3.45
    eta.ka ~ 0.6
    eta.cl ~ 0.3
    eta.v ~ 0.1
    add.sd <- 0.7
  })
  model({
    ka <- exp(tka + eta.ka)
    cl <- exp(tcl + eta.cl)
    v <- exp(tv + eta.v)
    cp <- linCmt()
    cp ~ add(add.sd)
  })
}

ui <- nlmixr2(one.compartment)
ui %>%
  model(
    f(central) <- 1 + f_study1*(STUDYID == 1),
    append = NA
  )
#> ℹ add residual parameter `f_study1` and set estimate to 1
#> ℹ add residual parameter `STUDYID` and set estimate to 1
#>  ── rxode2-based solved PK 1-compartment model with first-order absorption ────── 
#>  ── Initalization: ──  
#> Fixed Effects ($theta): 
#>      tka      tcl       tv   add.sd f_study1  STUDYID 
#>     0.45     1.00     3.45     0.70     1.00     1.00 
#> 
#> Omega ($omega): 
#>        eta.ka eta.cl eta.v
#> eta.ka    0.6    0.0   0.0
#> eta.cl    0.0    0.3   0.0
#> eta.v     0.0    0.0   0.1
#>  ── μ-referencing ($muRefTable): ──  
#>   theta    eta level
#> 1   tka eta.ka    id
#> 2   tcl eta.cl    id
#> 3    tv  eta.v    id
#> 
#>  ── Model (Normalized Syntax): ── 
#> function() {
#>     ini({
#>         tka <- 0.45
#>         tcl <- 1
#>         tv <- 3.45
#>         add.sd <- c(0, 0.7)
#>         f_study1 <- 1
#>         STUDYID <- 1
#>         eta.ka ~ 0.6
#>         eta.cl ~ 0.3
#>         eta.v ~ 0.1
#>     })
#>     model({
#>         f(central) <- 1 + f_study1 * (STUDYID == 1)
#>         ka <- exp(tka + eta.ka)
#>         cl <- exp(tcl + eta.cl)
#>         v <- exp(tv + eta.v)
#>         cp <- linCmt()
#>         cp ~ add(add.sd)
#>     })
#> }

^{Created on 2022-12-12 with reprex v2.0.2}

[mattfidler]

The problem here is that the parameter STUDYID is identified (incorrectly) as a residual parameter.

In theory you simply need to use model({}, auto=FALSE), so I believe this is actually a bug.

[mattfidler]

It works with the latest development version