Hello,
In the documentation for ?rep, sections Value and Note say that
> Value
> An object of the same type as x.
> rep.int and rep_len return no attributes (except the class if
returning a factor).
> The default method of rep gives the result names (which will almost
always contain duplicates) if x had names, but retains no other
attributes.
> Note
> Function rep.int is a simple case which was provided as a separate
function partly for S compatibility and partly for speed (especially
when names can be dropped). The performance of rep has been improved
since, but rep.int is still at least twice as fast when x has names.
And this works as documented.
y <- 1:4
names(y) <- letters[1:4]
class(y) <- "new_class"
attr(y, "this") <- "that"
y
#> a b c d
#> 1 2 3 4
#> attr(,"class")
#> [1] "new_class"
#> attr(,"this")
#> [1] "that"
rep(y, 2) # keeps names only
#> a b c d a b c d
#> 1 2 3 4 1 2 3 4
rep.int(y, 2) # no names and no other attributes
#> [1] 1 2 3 4 1 2 3 4
rep_len(y, 2) # no names and no other attributes
#> [1] 1 2
But in the documentation's last example, the factor example, the names
attribute is not dropped.
## named factor
x <- factor(LETTERS[1:4]); names(x) <- letters[1:4]
x
#> a b c d
#> A B C D
#> Levels: A B C D
rep(x, 2)
#> a b c d a b c d
#> A B C D A B C D
#> Levels: A B C D
rep(x, each = 2)
#> a a b b c c d d
#> A A B B C C D D
#> Levels: A B C D
rep.int(x, 2) # no names <--- Wrong comment
#> a b c d a b c d
#> A B C D A B C D
#> Levels: A B C D
rep_len(x, 10)
#> a b c d a b c d a b
#> A B C D A B C D A B
#> Levels: A B C D
Further test with attributes()
rep.int(x, 2) |> attributes()
#> $names
#> [1] "a" "b" "c" "d" "a" "b" "c" "d"
#>
#> $class
#> [1] "factor"
#>
#> $levels
#> [1] "A" "B" "C" "D"
rep_len(x, 10) |> attributes()
#> $names
#> [1] "a" "b" "c" "d" "a" "b" "c" "d" "a" "b"
#>
#> $class
#> [1] "factor"
#>
#> $levels
#> [1] "A" "B" "C" "D"
If I'm reading the docs right, this is wrong, isn't it?
Hope this helps,
Rui Barradas
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