You could put this data into a 3 dimensional array and then use the apply function to apply a function (such as mean) over which ever variables you choose.
Or you could put the data into a data frame in long format where you have your 3 variable indices in 3 columns, then the data in a 4th column. Then use the tapply function to apply the mean (or other function) to groups based on the indices of choice. If you want to do fancier things in either case then look into the reshape2 and plyr packages for ways of shaping the data and taking the data apart into pieces, apply a function to each piece, then put it all back together again. On Tue, Mar 20, 2012 at 11:16 AM, jorge Rogrigues <hjm...@gmail.com> wrote: > Suppose I have data organized in the following way: > (P_i, M_j, S_k) > > where i, j and k and indexes for sets. > I would like to analyze the data to get for example the following > information: > what is the average over k for > (P_i, M_j) > or what is the average over j and k for P_i. > > My question is what would be the way of doing this in R. > Specifically how should I write the data in a csv file > and how do I read the data from the csv file into R and perform these basic > operations. > > Thank you. > > [[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. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com ______________________________________________ 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.
