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.