Thanks for helping me see why R doesn't have the "obvious"! -Bob > -----Original Message----- > From: Thomas Lumley [mailto:[EMAIL PROTECTED] > Sent: Monday, August 27, 2007 2:12 PM > To: Muenchen, Robert A (Bob) > Subject: RE: [R] subset using noncontiguous variables by name (not > index) > > On Mon, 27 Aug 2007, Muenchen, Robert A (Bob) wrote: > > > Thomas, that's a good point. I was thinking of anscombe[x1::y1] > making > > it clear which one, but you would then want just x1::y1 to have > > unambiguous meaning on its own, which is impossible. > > > > As for x1:xN, it's unambiguous on its own. > > > It actually isn't. We already have a meaning. Consider > x1<-4 > xN<-6 > x1:xN > It also breaks R's argument passing rules by treating x1 as string > rather than a name. > > What would be unambiguous at the moment is "x1":"x4", provided there > was a sufficiently precise set of rules on what was allowed. Consider > "x1":"x-1" (negative?) > "x1":"x3.14" (non-integer?) > "x3.12":"x3.14" (is the prefix x or x3.?) > "x1":"X4" (the prefix changes) > "01":"14" (is the prefix empty or 0?) > "x09":"xA2" (is this illegal decimal or legal hexadecimal?) > "IL23R1":"IL23R4" (what is the prefix?) > "x1a":"x4a" (infix numbering?) > > > > -thomas > > Thomas Lumley Assoc. Professor, Biostatistics > [EMAIL PROTECTED] University of Washington, Seattle >
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