Trivial speed example in R

speedtest.R

method.list <- list(
    slow = function(iter) {
        var <- NULL;
        for (i in 1:iter) {
            var <- c(
                var,
                sqrt(i)
                );
            }
        var
        },  
    medium = function(iter) { 
        var <- rep(NA, iter);
        for (i in 1:length(var)) {
            var[i] <- sqrt(i)
            }
        var
        },
    fast = function(iter) {
        sqrt(1:iter);
        }
    );

lapply(method.list, function(FUN, x) { system.time({ FUN(x) }) }, x = 1e5)