24.6 Avoiding Input Coercion

• as.data.frame() is quite slow because it coerces each element into a data frame and then rbind()s them together
• instead, if you have a named list with vectors of equal length, you can directly transform it into a data frame

quickdf <- function(l) {
  class(l) <- "data.frame"
  attr(l, "row.names") <- .set_row_names(length(l[[1]]))
  l
}
l <- lapply(1:26, function(i) runif(1e3))
names(l) <- letters
bench::mark(
  as.data.frame = as.data.frame(l),
  quick_df      = quickdf(l)
)[c("expression", "min", "median", "itr/sec", "n_gc")]
#> # A tibble: 2 × 4
#>   expression         min   median `itr/sec`
#>   <bch:expr>    <bch:tm> <bch:tm>     <dbl>
#> 1 as.data.frame  959.5µs   1.01ms      973.
#> 2 quick_df         6.3µs   7.08µs   132966.

Caveat! This method is fast because it’s dangerous!