If you just want a list of matrices and their counts, you can use Peter's list of matrices, L, and then:
With plyr: require(plyr) count(unlist(lapply(L, toString))) Without plyr: as.data.frame(table(unlist(lapply(L, toString)))) Cheers, Jeff. On Sat, Oct 9, 2010 at 12:44 PM, Peter Ehlers <ehl...@ucalgary.ca> wrote: > On 2010-10-07 10:10, Jim Silverton wrote: >> >> Hello, >> I gave a list of 2 x 2 matrices called matlist. I have about 5000 2 x 2 >> matrices. I would like to count how many of each 2 x 2 unique matrix I >> have. >> So I am thinking that I need a list of the unique 2 x 2 matrices and their >> counts. Can anyone help. >> > > Here's one way, using the plyr package: > > require(plyr) > ## make a list of 2X2 matrices > L <- vector('list', 5000) > set.seed(4321) > for(i in 1:5000) L[[i]] <- matrix(round(runif(4), 1), 2, 2) > > ## convert each matrix to a string of 4 numbers, then > ## form dataframe > dL <- ldply(L, function(.x) toString(unlist(.x))) > > ## add an index vector > dL$ind <- seq_len(5000) > > ## count unique strings; return string, frequency, indeces > result <- ddply(dL, .(V1), summarize, > freq=length(V1), > idx=toString(ind)) > > > -Peter Ehlers > > ______________________________________________ > 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. > ______________________________________________ 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.