Sequential for loop benchmark

set.seed(107)
n <- 1000000
m <- 10000
td <- data.frame(val=rnorm(n), id=sample(m, n, replace=TRUE))

start <- proc.time()[3]
res <- rep(0, NROW(td))
for (i in unique(td$id))
  res[td$id == i] <- mean(td$val[td$id != i])
elapsed <- proc.time()[3] - start

library(digest)
cat("Sequential for loop:\n")
cat(sprintf("Elapsed time: %f, MD5 hash: %s\n", elapsed, digest(res)))