>>>>> Shane Mueller >>>>> on Sat, 23 May 2020 00:37:57 -0400 writes:
> 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 I agree with Shane. I think this is a small "wart" that we should remove, ... and I have been testing a version of your code addition, and plan to commit that (once I've added regression tests etc). Martin ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel