Extract dates from dataframe
Try this:
library(gsubfn)
# convert date strings to dd-mm-yy
Dates <- gsub("/", "-", dat$Dates)
# regular expressiont to match dates
re <- "\\d\\d-\\d\\d-\\d\\d"
# extract dates and convert them to Date class
# giving a list d each of whose components is a vector of dates
d <- strapply(Dates, re, ~ as.Date(x, "%d-%m-%y"), perl = TRUE)
names(d) <- dat$ID
# combine them into a single data frame
do.call(rbind, lapply(dat$ID, function(id) data.frame(ID = id, Date = d[[id]])))
On Fri, Mar 6, 2009 at 6:17 AM, bartjoosen <bartjoosen at hotmail.com> wrote:
Hi,
I have the following dataframe:
? ID ? ? ? ? ? ? ? ? ? ? ? ? ? ?Dates
?1 ? ? ? ? ? ? ? 16-07-01 ?06-10-95
?2 ? ? ? ? ? ?24/01/02 ? ? 06-10-95
?3 16/01/02 ? 16/08/94 ? ? 12/01/91
And I would like to extract the dates, but couple the ID's to the right
dates, eg:
ID ?Dates
1 ? ?16-07-01
1 ? ?06-10-95
2 ? ?24-01-02
2 ?....
I have no clue about how to get started, looks something for the
regexp/grep/... kind of functions, but I don't get the point.
Any thoughts??
Kind regards
Bart Joosen
PS: for the reconstruction of the dataframe:
dat <-
structure(list(ID = c(1, 2, 3), Dates = structure(c(2L, 4L, 6L
), .Label = c("16-01-02 ? 16-08-94", "16-07-01 ?06-10-95", "24-01-02
06-10-95",
"24/01/02 ? ? 06-10-95", "16/01/02 ? 16/08/94", "16/01/02 ? 16/08/94
12/01/91"
), class = "factor")), .Names = c("ID", "Dates"), row.names = c(NA,
3L), class = "data.frame")
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