[R] backticks

[Gabor Grothendieck]

On 12/4/06, Peter Dalgaard <P.Dalgaard at biostat.ku.dk> wrote:
> Robin Hankin wrote:
> > Peter
> >
> > Aha!  so R backticks work just like bash backticks  (duh!)
> >
>
> Er, no. Backticks in shells have a command inside that will be evaluated
> and replaced by its output. (This is a bit confusing, but single and
> double quotes were already taken at the time...)

This shell-like behavior is also available in the gsubfn package
which allows one to process string arguments in arbitrary functions
using backticks by prefacing the function in question with fn$.
For example, by prefacing cat with fn$ we have:

   > library(gsubfn)
   > fn$cat("pi = $pi, pi/2 = `pi/2`\n")
   pi = 3.14159265358979, pi/2 = 1.57079632679490

>
> > unless they are on the LHS of an assignment.
> >
> > [We bash people now use $(...) instead]
> >
> > Could we add something to this effect to Quotes.Rd?
> >
> >
> > rksh
> >
> >
> > On 4 Dec 2006, at 14:33, Peter Dalgaard wrote:
> >
> >
> >> Robin Hankin wrote:
> >>
> > [snip]
> >
> >>> What exactly do backticks do that single or double quotes don't?
> >>>
> >>>
> >> I don't know whether we really want to be that dogmatic about it,
> >> but in
> >> a nutshell
> >>
> >> `like this` <- 2
> >> "like that" <- 3
> >> print(`like this`)
> >> print("like that")
> >>
> >> I.e. backtick'ed names work whereever ordinary names do, but quoted
> >> names work only on the LHS of assignments.
> >>
> >> The note in ?formula should probably be understood defensively: We
> >> intend backtick'ed names to work in all contexts, but  there may be
> >> programming practices where the backticks are not preserved
> >> (notably if
> >> there is a deparse-reparse step involved).
> >>
> >>
> >>> Where do I look for documentation on this?
> >>>
> >>>
> >>>
> >>>
> >>> --
> >>> Robin Hankin
> >>> Uncertainty Analyst
> >>> National Oceanography Centre, Southampton
> >>> European Way, Southampton SO14 3ZH, UK
> >>>   tel  023-8059-7743
> >>>
> >>> ______________________________________________
> >>> R-help at stat.math.ethz.ch mailing list
> >>> https://stat.ethz.ch/mailman/listinfo/r-help
> >>> PLEASE do read the posting guide http://www.R-project.org/posting-
> >>> guide.html
> >>> and provide commented, minimal, self-contained, reproducible code.
> >>>
> >>>
> >> --
> >>    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
> >>
> >
> > --
> > Robin Hankin
> > Uncertainty Analyst
> > National Oceanography Centre, Southampton
> > European Way, Southampton SO14 3ZH, UK
> >   tel  023-8059-7743
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
>
> --
>   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
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>