# File name: loop_apply.r my.loop <- 20 m.dim <- list(nrow = 200000, ncol = 10) m <- matrix(1, nrow = m.dim$nrow, ncol = m.dim$ncol) ret <- 0 start <- Sys.time() for(k in 1 : my.loop){ ret <- ret + sum(apply(m, 1, sum)) } Sys.time() - start