Here is a way to do it by reading in 60 lines at a time and computing the means:
# create some test data n <- 360 x <- matrix(runif(360*16800), nrow=16800) cat(x, file="/tempxx.txt") # now process the data 60 lines at a time, averaging each 60x60 block result <- matrix(0, nrow=6, ncol=280) nextLine <- 1 # next output in the result # create a list of indices to use to partition the input matrix colIndex <- split(seq(16800), (seq(16800) - 1) %/% 60) input <- file("/tempxx.txt", "r") while (TRUE){ # use 'scan' to read in 60 lines at a time block <- scan(input, what=0, n=60*16800) if (length(block) != 60 * 16800) break # exit if done # convert to a matrix block <- matrix(block, nrow=60, byrow=TRUE) # compute the mean and store it result[nextLine,] <- sapply(colIndex, function(.blk){ mean(block[, .blk]) }) nextLine <- nextLine + 1 } On Sun, Sep 7, 2008 at 4:46 PM, Steve Murray <[EMAIL PROTECTED]> wrote: > > Gabor - thanks for your suggestion... I had checked the previous post, but I > found (as a new user of R) this approach to be too complicated and I had > problems gaining the correct output values. If there is a simpler way of > doing this, then please feel free to let me know. > > Dylan - thanks, your approach is a good start. In answer to your questions, > my data are 43200 columns and 16800 rows as a data frame - I will probably > have to read the dataset in segments though, as it won't fit into the memory! > I've been able to follow your example - how would I be able to apply this > technique for finding the average of each 60 x 60 block? > > Any other suggestions are of course welcome! > > Many thanks again, > > Steve > > _________________________________________________________________ > Discover Bird's Eye View now with Multimap from Live Search > > ______________________________________________ > 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. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? ______________________________________________ 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.