string assign is too strict for use in nlmixr2est

[mattfidler]

By parsing a simple if/else and pruning it we get:

library(rxode2)
#> rxode2 3.0.0 using 8 threads (see ?getRxThreads)
#>   no cache: create with `rxCreateCache()`
f <- rxode2({
  levels(a) <- c("good", "bad")
  E0 <- THETA[1]
  Em <- THETA[2]
  E50 <- THETA[3]
  g <- 2
  v <- E0 + Em * time^g / (E50^g + time^g) + wt
  p <- expit(v)
  a <- (p < 0.5) * (1)
  a <- (1 - (p < 0.5)) * (2) + (1 - ((1 - (p < 0.5)))) * (a)
  rx_yj_ ~ 152
  rx_lambda_ ~ 1
  rx_low_ ~ 0
  rx_hi_ ~ 1
  rx_r_ ~ 0
  rx_pred_ ~ DV * v - log(1 + exp(v))
  rx_pred_ <- -rx_pred_
})
#> rxode2 model syntax error:
#> ================================================================================
#> :001:     levels(a) <- c("good", "bad")
#> :002:     E0 <- THETA[1]
#> :003:     Em <- THETA[2]
#> :004:     E50 <- THETA[3]
#> :005:     g <- 2
#> :006:     v <- E0 + Em * time^g/(E50^g + time^g) + wt
#> :007:     p <- expit(v)
#> :008: the string variable 'a' can only be 1 to 2, or 'good', 'bad':
#>           a <- (p < 0.5) * (1)
#>                ^~~~~~~~~~~~~~~~~~~~
#> :008:     a <- (p < 0.5) * (1)
#> :009: the string variable 'a' can only be 1 to 2, or 'good', 'bad':
#>           a <- (1 - (p < 0.5)) * (2) + (1 - ((1 - (p < 0.5)))) * (a)
#>                ^
#> :009:     rx_yj_ ~ 152
#> :010:     rx_lambda_ ~ 1
#> :011:     rx_low_ ~ 0
#> :012:     rx_hi_ ~ 1
#> :013:     rx_r_ ~ 0
#> :014:     rx_pred_ ~ DV * v - log(1 + exp(v))
#> :015:     rx_pred_ <- -rx_pred_
#> ================================================================================
#> Error: syntax errors (see above)

^{Created on 2024-08-31 with reprex v2.1.1}

[mattfidler]

While it works out to 1 or 2 the parser doesn't do algebra.