Thank you everyone. Indeed, I had read the data via read.csv and the date column was a factor. Everything works fine if I convert to character first.
Regards, b. --- Sundar Dorai-Raj <[EMAIL PROTECTED]> wrote: > > > bogdan romocea wrote: > > > Dear R users, > > > > I have a column with dates (character) in a data frame: > > 12-Jan-01 11-Jan-01 10-Jan-01 9-Jan-01 8-Jan-01 > 5-Jan-01 > > and I need to convert them to (Julian) dates so that I > can > > sort the whole data frame by date. I thought it would > be > > very simple, but after checking the documentation and > the > > list I still don't have something that works. > > > > 1. as.Date returns the error below. What am I doing > wrong? > > As far as I can see the character strings are in > standard > > format. > > d$Date <- as.Date(d$Date, format="%d-%b-%y") > > Error in fromchar(x) : character string is not in a > > standard unambiguous format > > > > 2. as.date {Survival} produces this error, > > d$Date <- as.date(d$Date, order = "dmy") > > Error in as.date(d$Date, order = "dmy") : Cannot coerce > to > > date format > > > > 3. Assuming all else fails, is there a text function > > similar to SCAN in SAS? Given a string like "9-Jan-01" > and > > "-" as separator, I'd like a function that can read the > > first, second and third values (9, Jan, 01), so that I > can > > get Julian dates with mdy.date {survival}. > > > > Thanks in advance, > > b. > > > > If you're reading this from a file (via read.table, for > example), then > your date column is probably a factor. Convert to > character first. > > > x > [1] 12-Jan-01 11-Jan-01 10-Jan-01 9-Jan-01 8-Jan-01 > 5-Jan-01 > Levels: 10-Jan-01 11-Jan-01 12-Jan-01 5-Jan-01 8-Jan-01 > 9-Jan-01 > > > > Date(x, format="%d-%b-%y") > Error in fromchar(x) : character string is not in a > standard unambiguous > format > > > > sort(as.Date(as.character(x), format="%d-%b-%y")) > [1] "2001-01-05" "2001-01-08" "2001-01-09" "2001-01-10" > "2001-01-11" > [6] "2001-01-12" > > > --sundar > > ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html