[R] Using GSUB to obtain a printing "\"

[William Dunlap]

gsub does this because the string "dsff\nfsd"
does not contain a backslash - the 5th character
is a newline.  The deparsed representation (used
for printing the string) of a newline is "\n" but
the string itself has not backslash.

You can feed the output of deparse into message (or
cat) so they show the backslash-n characters, but
you then have to remove the enclosing quotes that
deparse adds.

  > x<-"dsff\nfs\rd\1"
  > x
  [1] "dsff\nfs\rd\001"
  > message("x is ", deparse(x))
  x is "dsff\nfs\rd\001"
  > message("x is ", gsub("^\"|\"$", "", deparse(x)))
  x is dsff\nfs\rd\001
  > cat("x is", gsub("^\"|\"$", "", deparse(x)), "\n")
  x is dsff\nfs\rd\001 
  > cat(x) # this is with Windows Rgui.exe
  dsff
  fs
  d
> 

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com  

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Bhushan, Vipul
> Sent: Thursday, May 05, 2011 2:48 PM
> To: r-help at r-project.org
> Subject: [R] Using GSUB to obtain a printing "\"
> 
> Hello. I'd like to be able to print variable strings which 
> contain "\" as-is, without interpreting (for example) 
> "abcde\nuvxyz" as having an embedded newline (or whatever 
> other escaped instruction). 
> 
> To do this, I've tried gsub, and here's some of my output 
> (I've tried all kinds of variations to the arguments): 
> 
> > message(gsub("[\\]","\\\\","dsff\nfsd"))
> dsff
> fsd
> 
> but I would like to see:
> dsff\nfsd  
> (which is the output of message("dsff\\nfsd") )
> 
> I don't know why gsub doesn't accomplish this substitution. 
> How can I replace (for example), a "\" with "\\"? Any 
> suggestions would be greatly appreciated. (I know I can use 
> another language, or use inelegant brute force by writing a 
> new routine which cycles through each possible character that 
> could follow the single "\".) Watching the gsub echo at the R 
> prompt shows that it is gsub (and not message) not behaving 
> as I expected. 
> 
> 
> Other information which the posting guidelines say might help:
> > sessionInfo()
> R version 2.13.0 (2011-04-13)
> Platform: x86_64-apple-darwin10.7.0/x86_64 (64-bit)
> 
> locale:
> [1] C
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods 
>   base     
> 
> other attached packages:
> [1] Rd2roxygen_0.1-8 roxygen_0.1-2    digest_0.4.2    
> 
> loaded via a namespace (and not attached):
> [1] tools_2.13.0
> > Sys.getlocale()
> [1] "C"
> 
> Thanks very much!
> 
> ______________________________________________
> R-help at r-project.org 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.
>