Error using the 2 times the same variable with type = "prop_choro" and val_max > max(var)

[rCarto]

library(mapsf)
mtq <- mf_get_mtq()
mf_map(mtq, var = c("POP", "POP"), type = "prop_choro", 
       val_max = max(mtq$POP) + 1, add = FALSE) 
#> Error in `[<-.data.frame`:
#> ! duplicate subscripts for columns

[rCarto]

library(mapsf)
mtq <- mf_get_mtq()
mf_map(mtq, var = c("POP", "POP"), type = "prop_choro", 
       val_max = max(mtq$POP) + 1, add = FALSE)