# compute the mean of the columns and the rows of a matrix library(foreach) # generate the input matrix x <- matrix(rnorm(100 * 100), 100) # compute the mean of each column of x cmeans <- foreach(i=1:ncol(x), .combine=c) %do% mean(x[,i]) # check the results expected <- colMeans(x) print(all.equal(cmeans, expected)) # compute the mean of each row of x rmeans <- foreach(i=1:nrow(x), .combine=c) %do% mean(x[i,]) # check the results expected <- rowMeans(x) print(all.equal(rmeans, expected))