On Fri, May 22, 2020 at 9:55 PM David Winsemius <dwinsem...@comcast.net> wrote:
> The premise in the first few lines of your preamble is at odds (in the > logical sense) with my understanding of primitive function behavior. Try: > > data.frame(x=1:2,y=letters[1:2])[j=2, i=1] > > David > I had never seen naming indexes of the [] operator. The documentation of [] indicates that it does argument matching in a non-standard way, recommends against doing it, and states the [.data.frame behavior used in this example is 'undocumented'. In the example above a warning is thrown as well. Here is the [] documentation: Argument matching > Note that these operations do not match their index arguments in the > standard way: argument names are ignored and positional matching only is > used. So m[j = 2, i = 1] is equivalent to m[2, 1] and not to m[1, 2]. > > This may not be true for methods defined for them; for example it is not > true for the data.frame methods described in [.data.frame which warn if i > or j is named and have undocumented behaviour in that case. > > To avoid confusion, do not name index arguments (but drop and exact must > be named). > For the data frames operator [], i and j appear to be named and used arguments, as the following causes an unused argument error for k: data.frame(x=1:2,y=letters[1:2])[j=2, k=1] The analog for round() would be indexing with something like [k=1,] alone, which causes an unused argument error error for data frames, which is what I'm suggesting round(banana=3.5) should do. (note it works for matrix as documented). Best, Shane [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel