Windows版Rでweekdaysを英語表記にする

R

date - Get weekdays in English in R - Stack Overflow
参考になるようでならない。環境依存なのかも。

> Sys.setlocale("LC_TIME", "en_US")
[1] ""
Warning message:
In Sys.setlocale("LC_TIME", "en_US") :
  OS reports request to set locale to "en_US" cannot be honored

> Sys.setlocale("LC_TIME","English United States")
[1] ""
Warning message:
In Sys.setlocale("LC_TIME", "English United States") :
  OS reports request to set locale to "English United States" cannot be honored

> weekdays(Sys.Date()+0:6)
[1] "火曜日" "水曜日" "木曜日" "金曜日" "土曜日" "日曜日" "月曜日"
> Sys.setlocale("LC_TIME","us")
[1] "English_United States.1252"
> weekdays(Sys.Date()+0:6)
[1] "Tuesday"   "Wednesday" "Thursday"  "Friday"    "Saturday"  "Sunday"    "Monday"

ということで、環境変数をあらかじめセットしておくかRprofileにでも書いておくとよいでしょう。