Christian Brechbühler wrote: <snip> > >>> data.frame(val=1:3,row.names=letters[1:3])[,1] >>> >> [1] 1 2 3 >> >> but it's not obvious that the result should be named using the row.names >> and (in particular) whether or why it should differ from .....[[1]] and >> ....$val.
this might be a good argument, if not that [,1] returning a vector rather than a one-column data frame is already inconsistent (with [,1:2], for example). if [,1] were not dropping the data.frame class and were returning a data frame instead, it would be obvious the result should use row names. data.frame(val=1:3,row.names=letters[1:3])[,1,drop=FALSE] will keep the class and row names, though ?'[' says "drop: For matrices and arrays.". it doesn't mean that dropping row names (or dropping dimensions) isn't useful and handy in specific cases, but this makes it no less inconsistent. >> Given that for most purposes, extracting the relevant names would >> just be unnecessary red tape, I'd say that we can do without it. >> > > > Compare > > >> data.frame(val=1:3,row.names=letters[1:3])[,1] >> > [1] 1 2 3 > >> as.matrix(data.frame(val=1:3,row.names=letters[1:3]))[,1] >> > a b c > 1 2 3 > > X[,1] preserves row names if X is a matrix, and loses them if X is a data > frame. To me, this is ugly and inconsistent. > > One might argue that having names and dimnames at all is "red tape", and > wastes memory and computational efficiency -- after all, Fortran arrays had > no names. But R chose to drag along the names (sometimes), and it can be > very helpful to us humans. Now R should do it consistently. > i support this opinion. whether to have or not to have row names is a design decision, and both options may be reasonably argued for and against. but lack of consistency is seldom any good; r consistently lacks consistency. vQ ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
