On Thu, Jul 15, 2010 at 4:21 PM, Dennis Murphy <djmu...@gmail.com> wrote: > Hi: > > Tal was on the right track, but the function in package zoo that applies > here is rollapply(): > > library(zoo) > m<-matrix(seq(1,80),ncol=20, nrow=4) > t(apply(m, 1, function(x) rollapply(zoo(x), width = 5, FUN = mean, by = 5))) > [,1] [,2] [,3] [,4] > [1,] 9 29 49 69 > [2,] 10 30 50 70 > [3,] 11 31 51 71 > [4,] 12 32 52 72 > > The width argument determines the number of values per subgroup to process, > and by determines the spacing between 'windows' of values. Since the > objective here was to summarize nonoverlapping blocks of size 5, both width > and by have to be specified with the same value. >
Just to build on Dennis' solution rollapply will act column by column so we can reduce it slightly to: out <- t(rollapply(zoo(t(m)), 5, by = 5, mean)) dimnames(out) <- NULL # optional ______________________________________________ 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.
