Hi,
I would like to discuss whether the following behaviour in lists is
indeed intended:
###################################################
> sessionInfo()
R version 2.10.0 Under development (unstable) (2009-07-21 r48968)
i386-pc-mingw32
locale:
[1] LC_COLLATE=German_Germany.1252 LC_CTYPE=German_Germany.1252 [3]
LC_MONETARY=German_Germany.1252 LC_NUMERIC=C [5]
LC_TIME=German_Germany.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
###################################################
# case 1
x1 <- list(1, 2)
names(x1)[2]
# returns NULL
# case 2
x2 <- list(foo=1, 2)
names(x2)[2]
# returns ""
# case 3
x3 <- list(1, 2)
names(x3)[1] <- "foo"
names(x3)[2]
# returns NA
###################################################
Although I don't find it particularly good that 1) and 2) behave
differently, I can very well understand what happens and accept this.
I may also understand (on a technical level) what happens in 3), but I
find it very disturbing that these lines
x2 <- list(foo=1, 2)
x3 <- list(1, 2)
names(x3)[1] <- "foo"
produce different results.
?names says
" The name |""| is special: it is used to indicate that there is
no name
associated with an element of a (atomic or generic) vector. Subscripting
by |""| will match nothing (not even elements which have no name).
A name can be character |NA|, but such a name will never be matched and
is likely to lead to confusion."
If it "likely leads to confusion" why does the implementation use it?
Regards,
Bernd Bischl
