From Martin Maechler <maechler@stat.math.ethz.ch>  Fri Jan 16 18:12:32 1998
From: Martin Maechler <maechler@stat.math.ethz.ch> (Martin Maechler)
Date: Fri, 16 Jan 1998 19:12:32 +0100
Subject: data.frame(...) not constructing "1:n" row.names [diff.  S <--> R]
Message-ID: <199801161812.TAA09746@sophie.ethz.ch>

	[I think Doug Bates has already alluded to this, somewhere..]

In R, 	data.frame( ... )

does not construct row.names whereas in S, it does:

R:

> data.frame(x=1:2,y=3:4)
     x y
[1,] 1 3
[2,] 2 4
> row.names(data.frame(x=1:2,y=3:4))
NULL


S-plus:

> data.frame(x=1:2,y=3:4)
  x y 
1 1 3
2 2 4
> row.names(data.frame(x=1:2,y=3:4))
[1] "1" "2"

---------------------------------------------------------------------------

R core: Is there a good reason for this?

Well (as a member of R-core, I give my answer):

	Memory efficiency can be a good reason, actually...
	together with ``cleanness'' :  
		``1:n'' are the IMPLICIT DEFAULT row.names

We could stay at the current way `internally',
but make sure that all functions working on data.frames `d.f'
automatically work as if

	 row.names(d.f)   *was indeed* ==  paste(1:nrow(d.f)

Some of them maybe even are, (lm, glm, and their methods  ??)
but not 'print.data.frame' (a <primitive>)
nor  row.names(.) or dimnames(.) (also <primitive>).
(and if dimnames is fixed, rownames(.) [the one without "."] will also work].

It may well be that it is sufficient to upgrade

	print.data.frame
	dimnames
and	row.names  (which is trivial to fix).

On the other hand,

	attr(d.f, "row.names")    [yet another <primitive> !]

would also have to be fixed for `complete' S compatibility
which is less "clean".


Martin Maechler <maechler@stat.math.ethz.ch>			<><
Seminar fuer Statistik, ETH-Zentrum SOL G1;	Sonneggstr.33
ETH (Federal Inst. Technology)	8092 Zurich	SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1086
http://www.stat.math.ethz.ch/~maechler/
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data.frame(...) not constructing "1:n" row.names [diff. S <--> R]
Martin Maechler