[R] as.character and a formula

[Peter Dalgaard]

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.
 
> ? 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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