https://twitter.com/LuigiBiagini/status/1464260125003325451

vectors-not-loops.R

y <- runif(2000)

foo_loop <- function(y) {
  m <- length(y)
  res <- matrix(nrow = m, ncol = m)
  
  for (i in 1:m) {
    for (j in 1:m) {
      res[i, j] <- all(y[i] <= y[j])
    }
  }
  
  as.data.frame(res)
}

foo_vec <- function(y) {
  as.data.frame(sapply(seq_along(y), \(i) y <= y[i]))
}

bench::mark(foo_loop(y), foo_vec(y))
#> Warning: Some expressions had a GC in every iteration; so filtering is disabled.
#> # A tibble: 2 x 6
#>   expression       min   median `itr/sec` mem_alloc `gc/sec`
#>   <bch:expr>  <bch:tm> <bch:tm>     <dbl> <bch:byt>    <dbl>
#> 1 foo_loop(y)    2.52s    2.52s     0.397    46.4MB     10.7
#> 2 foo_vec(y)  117.52ms 150.16ms     6.01     76.7MB     15.0