Hello! My problem is that the Julian date "behind" my dates seems to be wrong. I will examplify my problem. t1 <- "1998-11-20" t2 <- as.Date(t1) # Here t2 is correctly "1998-11-20", but date.mdy(t2) $month [1] 11 $day [1] 19 $year [1] 1988 And indeed, if I write: fix(t2) then I get : structure(10550, class = "Date"). So the Julian date is 10550, which is "1988-11-19", not the correct "1998-11-20" If I instead of "as.Date" use "as.date", then things work ok. But I have not found out how to instruct "as.date" to handle dates from the 21st century. I hope that someone can help me, thanks in advance! -- Best regards, Vegard Andersen Institute of Community Medicine University of Tromso Tromso, Norway vegard.andersen at ism.uit.no
Vegard Andersen <vegard.andersen <at> ism.uit.no> writes:
:
: Hello!
:
: My problem is that the Julian date "behind" my dates seems to be
wrong. I
: will examplify my problem.
:
: t1 <- "1998-11-20"
: t2 <- as.Date(t1)
: # Here t2 is correctly "1998-11-20", but
: date.mdy(t2)
: $month
: [1] 11
: $day
: [1] 19
: $year
: [1] 1988
:
: And indeed, if I write: fix(t2) then I get : structure(10550, class =
: "Date"). So the Julian date is 10550, which is
"1988-11-19", not the
: correct "1998-11-20"
:
: If I instead of "as.Date" use "as.date", then things work
ok. But I have
: not found out how to instruct "as.date" to handle dates from the
21st
: century.
:
: I hope that someone can help me, thanks in advance!
:
As already mentioned the "date" class in survival uses 1960 as
its origin:
R> as.date(0)
[1] 1Jan60
whereas the "Date" class uses 1970:
R> structure(0, class = "Date")
[1] "1970-01-01"
Regarding your other question you can use a 4 digit year:
R> as.date("2Jan2001")
[1] 2Jan2001
or:
R> as.date.Date <- function(x) as.date(format(x), order =
"ymd")
R> as.date.Date(t2)
[1] 20Nov98