Thank you Peter. It was not my question but I was just about to start the morning's work by searching Help and RSiteSearch() for this exact question.
--- Peter Dalgaard <[EMAIL PROTECTED]> wrote: > stat stat wrote: > > Dear all, > > > > Suppose I have a date variable: > > > > c = "99/05/12" > > > > I want to extract the parts of this date like > month number, year and day. I can do it in SPSS. Is > it possible to do this in R as well? > > > > Rgd, > > > > > Yes. One way is to use substr(), e.g.: > > > substr(c,1,2) > [1] "99" > > as.numeric(substr(c,1,2)) > [1] 99 > > This also nicely sidesteps the ambiguity issue: 1999 > or 1899? May or > December? On the other hand, you'll get in trouble > if leading zeros are > sometimes absent (strsplit() or gsub() if you want > to pursue that route > further). > > For a more principled approach, use the time and > date handling tools. > Assuming that you can live with the system defaults > for 2-digit years, > > > strptime(c,format="%y/%m/%d") > [1] "1999-05-12" > > strptime(c,format="%y/%m/%d")$year > [1] 99 > > strptime(c,format="%y/%m/%d")$mon > [1] 4 > > strptime(c,format="%y/%m/%d")$mday > [1] 12 > > Beware the peculiarities of the entries defined by > POSIX standard, see > ?DateTimeClasses, and also: > > '%y' Year without century (00-99). If you use > this on input, which > century you get is system-specific. So > don't! Often values > up to 69 (or 68) are prefixed by 20 and > 70(or 69) to 99 by > 19. > > (I'm at a bit of a loss as to fixing up two digit > years once the damage > has been done. Presumably, you can just diddle the > year field, but I'm a > bit uneasy about the fact that 2000 was a leap year > and 1900 was not.) > > > > -- > O__ ---- Peter Dalgaard Øster > Farimagsgade 5, Entr.B > c/ /'_ --- Dept. of Biostatistics PO Box 2099, > 1014 Cph. K > (*) \(*) -- University of Copenhagen Denmark > Ph: (+45) 35327918 > ~~~~~~~~~~ - ([EMAIL PROTECTED]) > FAX: (+45) 35327907 > > ______________________________________________ > [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 > and provide commented, minimal, self-contained, > reproducible code. > ______________________________________________ [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 and provide commented, minimal, self-contained, reproducible code.
