[Rd] row names and identical

[miguel manese]

I mean, starting 2.4 not all row names are stored as characters, some
are stored as integers.

On 7/16/07, miguel manese <jjonphl at gmail.com> wrote:
> I was bit by this before. row.names are supposed to be characters, and
> they are until around 2.3 iirc. Then at 2.4, they started storing it
> as integers presumably to save space (and probably because ints are
> more low-maintenance data types than strings). So to the user (e.g.
> through row.names() ) they are still characters, but internally they
> are not. I don't know what c(NA, 4L) stands for though (I see that it
> has 4 elems...), or why the other is c(NA, -4L). However, in my code I
> access them as a vector of integers,
>
> rownames = getAttrib(df, R_RowNamesSymbol);
> if (IS_INTEGER(rownames)) {
>     for (int i = 0; i < LENGTH(rownames); i++) foo(INTEGER(rownames)[i] ...);
> }
>
> Cheers,
> M. Manese
>
> On 7/15/07, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> > Below x1, x2 and x3 all have the same data and all have the same value
> > for row.names(x); however, the internal values of their row.names differ.
> > The internal value of row.names is c(NA, -4L) for x1, c(NA, 4L) for x2 and
> > c("1", "2", "3", "4") for x3; nevertheless, identical regards x1 and x2 as
> > identical while x3 is not identical to either of x1 or x2.
> >
> > Is this intended?
> > Desirable?
> > Why do we need different internal representations for row.names
> > for x1 and x2?
> >
> >
> > > x1 <- x2 <- x3 <- data.frame(x = 11:14)
> > > row.names(x2) <- 1:4
> > > row.names(x3) <- as.character(1:4)
> > >
> > > # they all have the same value for row.names()
> > > row.names(x1)
> > [1] "1" "2" "3" "4"
> > > row.names(x2)
> > [1] "1" "2" "3" "4"
> > > row.names(x3)
> > [1] "1" "2" "3" "4"
> > >
> > > # but internally they are all different
> > > dput(x1)
> > structure(list(x = 11:14), .Names = "x", row.names = c(NA, -4L
> > ), class = "data.frame")
> > > dput(x2)
> > structure(list(x = 11:14), .Names = "x", row.names = c(NA, 4L
> > ), class = "data.frame")
> > > dput(x3)
> > structure(list(x = 11:14), .Names = "x", row.names = c("1", "2",
> > "3", "4"), class = "data.frame")
> > >
> > > # identical regards x1 and x2 as the same while x3 differs
> > > identical(x1, x2)
> > [1] TRUE
> > > identical(x1, x3)
> > [1] FALSE
> > > identical(x2, x3)
> > [1] FALSE
> > >
> > > R.version.string # XP
> > [1] "R version 2.5.1 (2007-06-27)"
> >
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> >
>