On Thu, Nov 29, 2018 at 10:51 AM S Ellison <s.elli...@lgcgroup.com> wrote: > > > When trying out some variations with `[.data.frame` I noticed some (to me) > > odd behaviour, > > Not just in 'myfun' ... > > plot(x=1:10, y=) > plot(x=1:10, y=, 10:1) > > In both cases, 'y=' is ignored. In the first, the plot is for y=NULL (so not > 'missing' y) > In the second case, 10:1 is positionally matched to y despite the intervening > 'missing' 'y=' > > So it isn't just 'missing'; it's 'not there at all'
What exactly is the difference between "missing" and "not there at all"? --Ista > > Steve E > > > -----Original Message----- > > From: R-devel [mailto:r-devel-boun...@r-project.org] On Behalf Of Emil > > Bode > > Sent: 29 November 2018 10:09 > > To: r-devel@r-project.org > > Subject: [Rd] Unexpected argument-matching when some are missing > > > > 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 > > > > ******************************************************************* > This email and any attachments are confidential. Any u...{{dropped:11}} ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
