backticks
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
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-- 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 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 ?ster 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.