Here's another way, using the reshape2 package: library(reshape2) d <- dcast(df, vial ~ measure, value_var = 'value') d$diff <- with(d, B - A) > d vial A B diff 1 1 12 26 14 2 2 30 45 15 3 3 27 32 5 4 4 6 34 28
HTH, Dennis On Fri, Oct 21, 2011 at 3:31 PM, Nathan Miller <natemille...@gmail.com> wrote: > Hi all, > > Say I have a data frame something like the one below with different sample > vials, measured before(B) and after(A) some process, with a value recorded > at each measurement point > > vial measure value > 1 B 26 > 1 A 12 > 2 B 45 > 2 A 30 > 3 B 32 > 3 A 27 > 4 B 34 > 4 A 6 > > Is there an easy means by which I can subtract the after (A) measurements > from the before (B) measurement for each vial in this data frame so I am > left with a data frame that contains the vial number and difference between > A and B? I've played around with writing a function and applying it with > ddply, but haven't stumbled on a technique that works, though I feel there > should be something simple means of doing this that I'm just not seeing. > > Thanks for you help, > Nate > > [[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.
