Hi all, I'm working with a sizable dataset that I'd like to summarize, but I can't find a tool or function that will do quite what I'd like. Basically, I'd like to summarize the data by fully crossing three variables and getting a count of the number of observations for every level of that 3-way interaction. For example, if factors A, B, and C each have 3 levels (all of which were observed someplace in the dataset), I'd like to know how many times A1, B1, and C1 co-occurred in the dataset. Functions like aggregate and summaryBy do a decent job when I sum a vector of ones of the same length as the original dataset, but I'm getting stuck on the fact that neither will return 0-count combinations of the three variables in question. I understand that this is a desirable outcome (if A1, B1, C2 didn't occur, it shouldn't be counted and isn't), but I need to know both when these combinations of factor did and did not occur. I'm stuck on this one, and would really appreciate any help. Thanks in advance!
Dave Warren PS A functional solution would be best; the original dataset contains about 2.3 million observations, so any looping is going to be very slow. -- Post-doctoral Fellow Neurology Department University of Iowa Hospitals and Clinics davideugenewar...@gmail.com [[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.