[R] as.character and a formula

[Gavin Simpson]

On Tue, 2005-08-16 at 21:44 +0200, Peter Dalgaard wrote:
> Gavin Simpson <gavin.simpson at ucl.ac.uk> writes:
> 
> > Dear list,
> > 
> > given this formula: 
> > 
> > > fmla <- formula(y1 ~ spp1 + spp2 + spp3 + spp5)
> > > fmla[[3]]
> > spp1 + spp2 + spp3 + spp5
> > 
> > is this the intended behaviour of as.character:
> > 
> > > as.character(fmla[[3]])
> > [1] "+"                  "spp1 + spp2 + spp3" "spp5"
> 
> Yes.

Thanks Uwe, Brian and Peter for setting me straight. Being unobservant,
forgetful and stupid, all in one day, is some going, even for me.

All the best,

Gav

> > ? Where does the extra "+" come from?
> 
> What extra "+" ? There are three of them in fmla[[3]] and three in
> as.character(....).
> 
> as.character of an object of mode call is obtained by converting it to
> a list and deparsing each term (modulo some details regarding
> backquotes). This is somewhat peculiar, but quite a bit of legacy code
> is depending on it. Things like testing for as.character(e)[1] == "~"
> 
> 
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Gavin Simpson                     [T] +44 (0)20 7679 5522
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