Try this: > Lines <- "ID x y time + 1 10 20 0 + 1 10 30 1 + 1 10 40 2 + 2 12 23 0 + 2 12 25 1 + 2 12 28 2 + 2 12 38 3 + 3 5 10 0 + 3 5 15 2" > DF <- read.table(textConnection(Lines), header = TRUE) > aggregate(DF[3], DF[1:2], function(x) tail(x, 1) - head(x, 1)) ID x y 1 3 5 5 2 1 10 20 3 2 12 15
On Fri, Jan 2, 2009 at 4:20 AM, gallon li <gallon...@gmail.com> wrote: > I have the following data > > ID x y time > 1 10 20 0 > 1 10 30 1 > 1 10 40 2 > 2 12 23 0 > 2 12 25 1 > 2 12 28 2 > 2 12 38 3 > 3 5 10 0 > 3 5 15 2 > ..... > > x is time invariant, ID is the subject id number, y is changing over time. > > I want to find out the difference between the first and last observed y > value for each subject and get a table like > > ID x y > 1 10 20 > 2 12 15 > 3 5 5 > ...... > > Is there any easy way to generate the data set? > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. > ______________________________________________ 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.
