When trying out some variations with `[.data.frame` I noticed some (to me) odd
behaviour, which I found out has nothing to do with `[.data.frame`, but rather
with the way arguments are matched, when mixing named/unnamed and
missing/non-missing arguments. Consider the following example:
myfun <- function(x,y,z) {
print(match.call())
cat('x=',if(missing(x)) 'missing' else x, '\n')
cat('y=',if(missing(y)) 'missing' else y, '\n')
cat('z=',if(missing(z)) 'missing' else z, '\n')
}
myfun(x=, y=, "z's value")
gives:
# myfun(x = "z's value")
# x= z's value
# y= missing
# z= missing
This seems very counterintuitive to me, I expect the arguments x and y to be
missing, and z to get “z’s value”.
When I call myfun(,y=,"z's value"), x is missing, and y gets “z’s value”.
Are my expectations wrong or is this a bug? And if my expectations are wrong,
where can I find more information on argument-matching?
My gut-feeling says to call this a bug, but then I’m surprised no-one else has
encountered it before.
And I don’t have multiple installations to work from, so could somebody else
confirm this (if it’s not my expectations that are wrong) for R-devel/other
R-versions/other platforms?
My setup: R 3.5.1, MacOS 10.13.6, both Rstudio 1.1.453 and R --vanilla from Bash
Best regards,
Emil Bode
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