On Thu, Mar 24, 2011 at 2:24 PM, Kevin Burnham <kburn...@gmail.com> wrote: > I have a data file with indicates pretest scores for a linguistics > experiment. The data are in long form so for each of 33 subjects there are > 400 rows, one for each item on the test, and there is a column called > ‘Correct’ that shows ‘C’ for a correct response and ‘E’ for an incorrect > response. I am trying to write a formula that will create a vector that > indicates the number of correct answers for each subject. > > nrow(pretestdata[(pretestdata$Subject=="1" & pretestdata$Correct=="C"),]) > > > > gives the number of correct responses for subject 1, but I would like a > vector that indicates the number correct for each of 33 subjects.
How about with(pretestdata, table(Subject, Correct)) ? Hadley -- Assistant Professor / Dobelman Family Junior Chair Department of Statistics / Rice University http://had.co.nz/ ______________________________________________ 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.
