Hi, I am trying to calculate the sum for each occurrence of the level of a factor in a very large matrix. In addition, I want to save that sum together with the information of the level of the factor and the level of a second factor.
My matrix looks like this: x<-matrix(c(1,1,1,2,2,3,3,1,1,7,7,7,4,4,2,2,7,7,1,1,1,1,1,1,2,5,5),9,3) I want to sum according to the levels in the first column and save the sum with the information of the level in the first and the second column in a new matrix. That is, I want output in the matrix of form: 1 7 3 2 4 2 3 2 3 1 7 10 The important thing is, that a factor level such as "1" in the example can re-occur many times. There are no regularities on the number of re-occurences etc. How could I do this efficiently (the matrix is large:>10^6 rows)? Many thanks!! -Ralph _________________________________________________________________ [[elided Hotmail spam]] ______________________________________________ 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.
