I want a list of the number of times some factor levels appear together, similar to the following SQL statement:
SELECT A, B, COUNT(C) FROM TBL GROUP BY A, B How do I do that with a data.frame in R? Thanks, Jesper Frickmann Statistician, Quality Control Novozymes North America Inc. 77 Perry Chapel Church Road Franklinton, NC 27525 USA Tel. +1 919 494 3266 [[alternative HTML version deleted]] ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html