[R] Backquote in R syntax

[Peter Dalgaard]

(Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> writes:

> Hi Folks,
> Can someone satisfy my curiosity (well, at least about
> the following query!)
> 
> Reading the draft proofs of an article I've been asked
> to look through, I find the typesetter has set what
> would normally be entered as
> 
>   source("xyz.R")   or   source('xyz.R')
> 
> as
> 
>   source(`xyz.R')
> 
> i.e. it has come out with an opening backquote, then
> xyz.R, then a closing forward quote. I suspect the
> intervention of "intelligent" software (à la Word's
> "clever quotes").
> 
> Well, the cure is clear and I'm not asking about that.
> But I got curious about what role the backquote might
> play in R syntax (if any). As a start I tried typing
> that in as it stands:
> 
>    source(`xyz.R')
> ## and then you get the "continuation +" as if it were
> ##   incomplete, so I tried a closing parenthesis:
> + )
> Error: unprotect_ptr: pointer not found
> 
> So it wasn't a mere syntax error (which would have caused
> an error message saying just that) -- using the backquote
> caused R to try to do something.
> 
> So now I'm wondering what the effect of "`" is, in R.
> 
> Statutory Declaration: I have performed an R Site Search
> for "backquote" obtaining 9 hits none of which seems to
> address this question.

?Quotes should put you straight. (And help.search("`") gets you there,
as does help.search("backtick"), although not help.search("back
quote"))

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