> -----Original Message----- > From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Mike > Miller > Sent: Wednesday, December 24, 2014 11:31 AM > To: R-Help List > Subject: [R] ave(x, y, FUN=length) produces character output when x is > character > > R 3.0.1 on Linux 64... > > I was working with someone else's code. They were using ave() in a way > that I guess is nonstandard: Isn't FUN always supposed to be a variant > of > mean()? The idea was to count for every element of a factor vector how > many times the level of that element occurs in the factor vector. > > > gl() makes a factor: > > > gl(2,2,5) > [1] 1 1 2 2 1 > Levels: 1 2 > > > ave() applies FUN to produce the desired count, and it works: > > > ave( 1:5, gl(2,2,5), FUN=length ) > [1] 3 3 2 2 3 > > > The elements of the first vector are irrelevant because they are only > counted, so we should get the same result if it were a character > vector, > but we don't: > > > ave( as.character(1:5), gl(2,2,5), FUN=length ) > [1] "3" "3" "2" "2" "3" > > The output has character type, but it is supposed to be a collection of > vector lengths. > > > Two questions: > > (1) Is that a bug in ave()? It certainly is unexpected. > > (2) What is the best way to do this sort of thing? > > The truth is that we start with a character vector and we want to > create > an integer vector that tells us for every element of the character > vector > how many times that string occurs. Here are two vectors of length 6 > that > should give the same result: > > > intvec <- c(4,5,6,5,6,6) > > charvec <- c("A","B","C","B","C","C") > > The code was used like this with integer vectors and it seemed to work: > > > ave( intvec, intvec, FUN=length ) > [1] 1 2 3 2 3 3 > > When a character vector came along, it would fail by producing a > character > vector as output: > > > ave( charvec, charvec, FUN=length ) > [1] "1" "2" "3" "2" "3" "3" > > This seems more appropriate, and it might always work, but is it OK?: > > > ave( rep(1, length(charvec)), as.factor(charvec), FUN=sum ) > [1] 1 2 3 2 3 3 > > I suspect that ave() isn't the best choice, but what is the best way to > do > this? > > > Thanks in advance. > > Mike
For your character vector example, this will get you the counts. table(charvec)[charvec] Hope this is helpful, Dan Daniel J. Nordlund, PhD Research and Data Analysis Division Services & Enterprise Support Administration Washington State Department of Social and Health Services ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
