Hi all,
I think there's an unnecessary line in [.Date which has a considerable
impact on performance when subsetting large dates:
x <- Sys.Date() + 1:1e6
microbenchmark::microbenchmark(x[1])
#> Unit: microseconds
#> expr min lq mean median uq max neval
#> x[1] 920.651 1039.346 3624.833 2294.404 3786.881 41176.38 100
`[.Date` <- function(x, ..., drop = TRUE) {
cl <- oldClass(x)
# class(x) <- NULL
val <- NextMethod("[")
class(val) <- cl
val
}
microbenchmark::microbenchmark(x[1])
#> Unit: microseconds
#> expr min lq mean median uq max neval
#> x[1] 2.738 3.0225 28.40893 3.269 3.513 2470.068 100
Setting the class of x to NULL is problematic because it forces a
copy, and I'm pretty sure it's unnecessary as NextMethod() does not
consult the class of x, but instead uses .Class.
Hadley
--
http://hadley.nz
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