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
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