table() is your friend:
> X <- factor(scan(what="")) 1: A B B C A C B A C C 11: Read 10 items > Y <- factor(scan(what="")) 1: B B C C C A A A B B 11: Read 10 items > table(X) X A B C 3 3 4 > table(X, Y) Y X A B C A 1 1 1 B 1 1 1 C 1 2 1 Andy > From: zhihua li > > hi netters > > Suppose I have a factor X, with 10 elements and 3 levels: A B > B C A C B A C > C . > > It is easy to count the number of elements for each level: > tapply(X,X,length). > > Now I have another factor Y, which formed a matrix with X: > > X| A B B C A C B A C C > Y| B B C C C A A A B B > > I wanna count the number of elements for each of these > conditions: when X=A > and Y=A; when X=A and Y=B; when X=A and Y=C; when X=B and > Y=A; when X=B and > Y=B; when X=B and Y=C; when X=C and Y=A; when X=C and Y=B; > when X=C and > Y=C. > > The code I have written for this task is too complicated, > involving a lot > of for loops and if conditions. I believe there's some nice > code that can > do it far more efficiently. Can anyone give me a hint? > > Thanks a lot! > > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
