The sample data you provided has the variable 'date'. Since the type of
this variable is 'factor', you may try to convert type of variable from
'factor' to 'date' as shown in the below:
> x$rval <- as.Date(x$date, format="%d%b%Y")-5
> x
id date case rval
1 1 27apr1993 1 1993-04-22
2 2 13feb2005 1 2005-02-08
3 3 29may2002 1 2002-05-24
4 4 22sep2005 1 2005-09-17
5 5 18dec1991 1 1991-12-13
6 6 07jun2010 1 2010-06-02
7 7 07jul1991 1 1991-07-02
8 8 04feb2008 1 2008-01-30
9 9 31jan2005 1 2005-01-26
10 10 01feb2003 1 2003-01-27
11 11 29jan2009 1 2009-01-24
12 12 03mar2008 1 2008-02-27
>
Leap year is also considered (See the last case 'id=12'). Is this what
you are looking for? I hope this helps.
Chel Hee Lee
On 12/11/2014 9:54 AM, Kuma Raj wrote:
Dear R Community,
I wish to create 5 preceding dates from the date variable by ID. How
could I create such dates? The code should consider leap year.
Thanks
Sample data follows:
structure(list(id = 1:12, date = structure(c(9L, 6L, 11L, 8L,
7L, 5L, 4L, 3L, 12L, 1L, 10L, 2L), .Label = c("01feb2003", "03mar2008",
"04feb2008", "07jul1991", "07jun2010", "13feb2005", "18dec1991",
"22sep2005", "27apr1993", "29jan2009", "29may2002", "31jan2005"
), class = "factor"), case = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L)), .Names = c("id", "date", "case"), class =
"data.frame", row.names = c(NA,
-12L))
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
