[Rd] factor(x, exclude=NULL) for factor x; names in as.factor(<integer>)

[Suharto Anggono Suharto Anggono]

In R 3.3.0 (also in R 2.7.2), the documentation on 'factor', in "Details" section, has this statement.
'factor(x, exclude = NULL)' applied to a factor is a no-operation unless there are unused levels: in that case, a factor with the reduced level set is returned.

It is not true for a factor 'x' that has NA. In that case, if levels of 'x' doesn't contain NA, factor(x, exclude = NULL) adds NA as a level.
If levels of a factor 'x' doesn't contain NA, factor(x) is a no-operation if all levels are used.


In R 3.3.0 (also in R 3.1.3), for a named integer 'x', factor(x) has names and as.factor(x) doesn't. It would be better if the behavior on names were matched.

> x <- integer(1)
> names(x) <- "a"
> names(factor(x))
[1] "a"
> names(as.factor(x))
NULL
> sessionInfo()
R version 3.3.0 (2016-05-03)
Platform: i386-w64-mingw32/i386 (32-bit)
Running under: Windows XP (build 2600) Service Pack 2

locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] tools_3.3.0