I think that's in general a trickier question: If you are absolutely certain your id's are in blocks and that there are at least k of them, it would perhaps work to do a manual adjustment of the indices:something like
# UNTESTED with(dat, dat[which(!duplicated(id)) + k - 1, ]) # where k is the whatever-eth element you want to look at If you aren't guaranteed a block structure, you might have to use some sort of "rinse and repeat" code (i.e., get the first occurrences, throw them out, get the new first occurrences = the old 2nd occurrences, etc). If you aren't certain that you have at least k occurences, you'll want to handle that as well. There might be a smarter way, but I'm not seeing one off hand One nice solution if you just want the last is to use the dupicated(, fromLast = TRUE) optional argument. Michael Weylandt On Sun, Sep 25, 2011 at 6:08 PM, AC Del Re <acde...@gmail.com> wrote: > perfect. Thank you, Michael. Out of curiosity, how would the code differ if > you were interested in selecting the second row (or third, etc) per id? > > Thanks again for your help. > > AC > > > On Sun, Sep 25, 2011 at 1:48 PM, R. Michael Weylandt < > michael.weyla...@gmail.com> wrote: > >> dat <- data.frame(id = c(1,1,1,2,2), value = c(5,6,7,4,5), value2 = >> c(1,4,3,3,4)) >> with(dat, dat[!duplicated(id),]) >> >> Michael >> >> >> On Sun, Sep 25, 2011 at 4:43 PM, AC Del Re <acde...@gmail.com> wrote: >> >>> Great but how can I then retain the other variable (or variables if >1) >>> value associated with those retained values? >>> thank you. >>> >>> On Sun, Sep 25, 2011 at 1:27 PM, R. Michael Weylandt < >>> michael.weyla...@gmail.com> wrote: >>> >>>> How about something like >>>> >>>> with(dat, value[!duplicated(id)]) >>>> >>>> ? >>>> >>>> Michael Weylandt >>>> On Sun, Sep 25, 2011 at 4:22 PM, AC Del Re <de...@wisc.edu> wrote: >>>> >>>>> Hi, >>>>> >>>>> I am trying to select the first row of a variable with data in >>>>> long-format, >>>>> e.g., >>>>> >>>>> # sample data >>>>> id <- c(1,1,1,2,2) >>>>> value <- c(5,6,7,4,5) >>>>> dat <- data.frame(id, value) >>>>> dat >>>>> >>>>> How can I select/subset the first 'value' for each unique 'id'? >>>>> >>>>> Thanks, >>>>> >>>>> AC >>>>> >>>>> [[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. >>>>> >>>> >>>> >>> >> > [[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.
