Note that ?transform.data.frame says arguments need to be named, so you
are testing unspecified behaviour. I guess this falls in a similar
category as the note
If some of the values are not vectors of the appropriate length,
you deserve whatever you get!
Experiments for a related Problem Report
(<https://bugs.r-project.org/show_bug.cgi?id=17890>) showed that
packages bravely ignore the caveats mentioned on the help page,
including to assume recycling the rows of the input data frame. I didn't
yet see any uses of unnamed arguments, though.
That said, I agree that transform.data.frame() should be improved. Maybe
unnamed arguments should always be ignored with a warning. My feeling is
that these would more often be usage errors than intentional, e.g.:
> data.frame(a = 1) |> transform(b = 2, a + 2) # "forgetting" a=
a b X3
1 1 2 3
I also think the implicit check.names=TRUE behaviour should be disabled. In
> list2DF(list(`A-1` = 1)) |> transform(B = 2)
A.1 B
1 1 2
transforming B should not touch the other columns.
I'm less sure about some other forms of undocumented behaviour as
described in Comment 6 of the linked PR.
Sebastian Meyer
Am 02.03.23 um 18:49 schrieb Antoine Fabri:
Dear r-devel,
See below:
transform(data.frame(a = 1), 2, 3)
#> a
#> 1 1
transform(data.frame(a = 1), b=2, 3)
#> a b X3
#> 1 1 2 3
We need a small modification to make it work consistently, see below:
transform.data.frame <- function (`_data`, ...) {
e <- eval(substitute(list(...)), `_data`, parent.frame())
tags <- names(e)
## NEW LINE -----------------------------------------------
if (is.null(tags)) tags <- character(length(e))
inx <- match(tags, names(`_data`))
matched <- !is.na(inx)
if (any(matched)) {
`_data`[inx[matched]] <- e[matched]
`_data` <- data.frame(`_data`)
}
if (!all(matched))
do.call("data.frame", c(list(`_data`), e[!matched]))
else `_data`
}
transform(data.frame(a = 1), 2, 3)
#> a X2 X3
#> 1 1 2 3
transform(data.frame(a = 1), b=2, 3)
#> a b X3
#> 1 1 2 3
Thanks,
Antoine
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