Re: [R] as.character and a formula

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Wed 17 Aug 2005 - 05:44:12 EST

Gavin Simpson <gavin.simpson@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] == "~"

-- 
   O__  ---- Peter Dalgaard             ุster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

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Received on Wed Aug 17 05:53:44 2005

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