> library(data.table)
data.table 1.17.0 using 6 threads (see ?getDTthreads).  Latest news: r-datatable.com
> load("../Tresorit/aux_.rdata")
> aux
        seqn                        area
       <int>                      <fctr>
    1:     1     Pontevedra-Ourense-Vigo
    2:     2 Coruña-Santiago-Ferrol-Lugo
    3:     3 Coruña-Santiago-Ferrol-Lugo
    4:     4     Pontevedra-Ourense-Vigo
    5:     5     Pontevedra-Ourense-Vigo
   ---                                  
14472: 14472     Pontevedra-Ourense-Vigo
14473: 14473     Pontevedra-Ourense-Vigo
14474: 14474 Coruña-Santiago-Ferrol-Lugo
14475: 14475 Coruña-Santiago-Ferrol-Lugo
14476: 14476     Pontevedra-Ourense-Vigo
> str(aux)
Classes ‘data.table’ and 'data.frame':  14476 obs. of  2 variables:
 $ seqn: int  1 2 3 4 5 6 7 8 9 10 ...
 $ area: Factor w/ 3 levels "","Coruña-Santiago-Ferrol-Lugo",..: 3 2 2 3 3 2 3 2 2 2 ...
 - attr(*, ".internal.selfref")=<externalptr> 
> levels(aux$area)
[1] ""                            "Coruña-Santiago-Ferrol-Lugo"
[3] "Pontevedra-Ourense-Vigo"    
> aux[area==""]
    seqn   area
   <int> <fctr>
1:  4207       
2:  6514       
> aux[seqn==6514, area := "Coruña-Santiago-Ferrol-Lugo"]
> levels(aux$area)
[1] ""                            "Coruña-Santiago-Ferrol-Lugo" "Pontevedra-Ourense-Vigo"     "Coruña-Santiago-Ferrol-Lugo"
> unique(levels(aux$area))
[1] ""                            "Coruña-Santiago-Ferrol-Lugo" "Pontevedra-Ourense-Vigo"    
> sessionInfo()
R version 4.4.2 (2024-10-31 ucrt)
Platform: x86_64-w64-mingw32/x64
Running under: Windows 11 x64 (build 26100)

Matrix products: default


locale:
[1] LC_COLLATE=English_United States.utf8  LC_CTYPE=English_United States.utf8    LC_MONETARY=English_United States.utf8
[4] LC_NUMERIC=C                           LC_TIME=English_United States.utf8    

time zone: Europe/Madrid
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] data.table_1.17.0

loaded via a namespace (and not attached):
[1] compiler_4.4.2 tools_4.4.2