[R] change language at console

[Martin Maechler]

>>>>> Rich Shepard via R-help 
>>>>>     on Tue, 18 Jul 2023 10:32:51 -0000 writes:

      > On Wed, 1 Apr 2015, Prof Brian Ripley wrote: 
      >  I would start by trying LANGUAGE=en , e.g. ͏ ​ ͏ ​ ͏ ​ ͏ ​ ͏ ​ ͏ ​ ͏ ​

  > More specifically, you can use en_US or en_GB.  Rich

"en_US" actually does not exist -- see below (but "en"
corresponds to it).

More relevantly, since R 4.2.0  we have

  Sys.setLanguage()

which does slightly more than setting LANGUAGE, notably
internally using  bindtextdomain() in a useful way, such that
the "translation cache" (of already translated messages) is flushed;
It was first considered in response to R's bugzilla issue PR#18055
  --> https://bugs.r-project.org/bugzilla/show_bug.cgi?id=18055

Note that help(Sys.setLanguage) 's examples
contain quite interesting R code , for example the following
(shown with R output here in R 4.3.1 with NLS (:=
Natural Language Support) enabled {as usual I think}, under
Linux (Fedora 36):


>  ## A show off of translations -- platform (font etc) dependent:
>  ## The translation languages available for "base" R in this version of R:

>      if(capabilities("NLS")) withAutoprint({
+        langs <- list.files(bindtextdomain("R"),
+                            pattern = "^[a-z]{2}(_[A-Z]{2}|@quot)?$")
+        langs
+        txts <- sapply(setNames(,langs),
+                       function(lang) { Sys.setLanguage(lang)
+                                       gettext("incompatible dimensions", domain="R-stats") })
+        cbind(txts)
+        (nTrans <- length(unique(txts)))
+        (not_translated <- names(txts[txts == txts[["en"]]]))
+      })
> langs <- list.files(bindtextdomain("R"), pattern = "^[a-z]{2}(_[A-Z]{2}|@quot)?$")
> langs
 [1] "da"      "de"      "en"      "en_GB"   "en using quot" "es"      "fa"      "fr"      "it"     
[10] "ja"      "ko"      "lt"      "nn"      "pl"      "pt_BR"   "ru"      "tr"      "zh_CN"  
[19] "zh_TW"  
> txts <- sapply(setNames(, langs), function(lang) {
+     Sys.setLanguage(lang)
+     gettext("incompatible dimensions", domain = "R-stats")
+ })
> cbind(txts)
        txts                            
da      "incompatible dimensions"       
de      "inkompatible Dimensionen"      
en      "incompatible dimensions"       
en_GB   "incompatible dimensions"       
en using quot "incompatible dimensions"       
es      "incompatible dimensions"       
fa      "incompatible dimensions"       
fr      "dimensions incompatibles"      
it      "dimensioni incompatibili"      
ja      " 矛盾した次元です "            
ko      "incompatible dimensions"       
lt      "nesuderinami matavimo skaičiai"
nn      "incompatible dimensions"       
pl      "niezgodne wymiary"             
pt_BR   "dimensões incompatíveis"       
ru      "несовместимые размерности"     
tr      "uyumsuz boyutlar"              
zh_CN   "维度不相配"                    
zh_TW   "維度不符合"                    
> (nTrans <- length(unique(txts)))
[1] 12
> (not_translated <- names(txts[txts == txts[["en"]]]))
[1] "da"      "en"      "en_GB"   "en using quot" "es"      "fa"      "ko"      "nn"     

---------------

In the original NEWS for R 4.2.0 ,
Sys.setLanguage() was labeled as "partly experimental"  but I
think in the mean time has shown some stability  and I'd
recommend its use {such that we find out if should be made even
more reliable}.

Martin

--
Martin Maechler
ETH Zurich  and  R Core team