Are you sure your data was the Date class? > x <- read.table('clipboard', header=TRUE) > x DATE DEATH 1207 2009-04-16 2009-05-06 1514 2009-04-16 2009-05-06 2548 2009-04-16 2009-05-08 3430 2009-04-16 2009-05-09 3851 2009-04-16 2009-05-09 3945 2009-04-16 2009-05-09 7274 2009-04-16 2009-05-12 7532 2009-04-16 2009-05-12 7651 2009-04-16 2009-05-12 8495 2009-04-16 2009-05-13 > ?as.Date > x$DATE <- as.Date(x$DATE) > x$DEATH <- as.Date(x$DEATH) > x$length <- x$DEATH - x$DATE > x DATE DEATH length 1207 2009-04-16 2009-05-06 20 days 1514 2009-04-16 2009-05-06 20 days 2548 2009-04-16 2009-05-08 22 days 3430 2009-04-16 2009-05-09 23 days 3851 2009-04-16 2009-05-09 23 days 3945 2009-04-16 2009-05-09 23 days 7274 2009-04-16 2009-05-12 26 days 7532 2009-04-16 2009-05-12 26 days 7651 2009-04-16 2009-05-12 26 days 8495 2009-04-16 2009-05-13 27 days
On Sun, Jun 20, 2010 at 8:13 PM, Erin Hodgess <erinm.hodg...@gmail.com> wrote: > Dear R People: > > I have a data frame with the two following date columns: > > >> a.df[1:10,c(1,6)] > DATE DEATH > 1207 2009-04-16 2009-05-06 > 1514 2009-04-16 2009-05-06 > 2548 2009-04-16 2009-05-08 > 3430 2009-04-16 2009-05-09 > 3851 2009-04-16 2009-05-09 > 3945 2009-04-16 2009-05-09 > 7274 2009-04-16 2009-05-12 > 7532 2009-04-16 2009-05-12 > 7651 2009-04-16 2009-05-12 > 8495 2009-04-16 2009-05-13 >> > > I would like to generate a 3rd column which is the difference in days > between the two dates. > > I tried > > a.df$DEATH - a.df$DATE > > but I obtain all NA. > > Any help would be much appreciated. > > Thanks, > Erin > > > > -- > Erin Hodgess > Associate Professor > Department of Computer and Mathematical Sciences > University of Houston - Downtown > mailto: erinm.hodg...@gmail.com > > ______________________________________________ > R-help@r-project.org 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. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? ______________________________________________ R-help@r-project.org 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.