Hi, It shouldn't be so complicated. What about simply:
> td vial measure value 2 1 A 12 1 1 B 26 4 2 A 30 3 2 B 45 6 3 A 27 5 3 B 32 8 4 A 6 7 4 B 34 > td <- td[order(td$vial, td$measure),] # make sure the samples are in order > # how to get the differences > td[td$measure == "B", "value"] - td[td$measure == "A", "value"] [1] 14 15 5 28 > > td.diff <- data.frame(vial = td[td$measure == "A", "vial"], diff = > td[td$measure == "B", "value"] - td[td$measure == "A", "value"]) > td.diff vial diff 1 1 14 2 2 15 3 3 5 4 4 28 > Sarah On Fri, Oct 21, 2011 at 6:31 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 > -- Sarah Goslee http://www.functionaldiversity.org ______________________________________________ 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.
