Since you did provide a description of your data (e.g., at least 'str(ALLDATA)') so that we know its structure, I will take a guess:
tapply(ALLDATA$Correct, list(ALLDATA$Subject, ALLDATA$Time), function(x)sum(x=="C")) On Sat, Apr 30, 2011 at 3:28 PM, Kevin Burnham <kburn...@gmail.com> wrote: > HI All, > > I have a long data file generated from a minimal pair test that I gave to > learners of Arabic before and after a phonetic training regime. For each of > thirty some subjects there are 800 rows of data, from each of 400 items at > pre and posttest. For each item the subject got correct, there is a 'C' in > the column 'Correct'. The line: > > tapply(ALLDATA$Correct, ALLDATA$Subject, function(x)sum(x=="C")) > > gives me the sum of correct answers for each subject. > > However, I would like to have that sum separated by Time (pre or post). Is > there a simple way to do that? > > > What if I further wish to separate by Group (T or C)? > > Thanks, > Kevin > > [[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. > -- Jim Holtman Data Munger Guru What is the problem that you are trying to solve? ______________________________________________ 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.