Dear all,
I would like to know the month on a string formatted as "2004-01",
using as.Date
(not just stripping the string !)
?as.Date says that in case of an incomplete input string, the answer is
system-specific.
The following has been tested on R 2.4.1, on Ubuntu Linux and WinXP.
> mydate <- "2004-01"
> as.Date(mydate)
Error in fromchar(x) : character string is not in a standard unambiguous format.
(I understand that).> as.Date(mydate,format="%Y-%m")
NA (is there still ambiguity in my format ??)
Investigating a bit, I found a strange behaviour in :
> as.Date("2004-01-12",format="%Y-%m-%d")
"2005-01-12"
> as.Date("2004-01",format="%Y-%m")
NA (why can't R see anything ?)
> as.Date("2004",format="%Y")
"2005-02-09" (month and day are replaced by today's values, normal
behaviour).
Why can't R see the month, but see the year ?
For the moment, I do this ugly thing :
> mydate <- paste(mydate,"-01",sep="") in order send
an unambiguous string to
as.Date.
Any idea how I can do better ?
Thanks and regards,
Nicolas Prune
