R help - Jun 2005 - How to convert "c:\a\b" to "c:/a/b"

I couldn't resist adding a more literal answer

unback <- function(x) {
  chars <- unlist(strsplit(deparse(x),""))
  chars <- chars[-c(1,length(chars))]
  paste(gsub("\\\\","/",chars),collapse="")
}

unback("\n")


| David Duffy (MBBS PhD)                                         ,-_|\
| email: davidD at qimr.edu.au  ph: INT+61+7+3362-0217 fax: -0101  /     *
| Epidemiology Unit, Queensland Institute of Medical Research   \_,-._/
| 300 Herston Rd, Brisbane, Queensland 4029, Australia  GPG 4D0B994A v

Close, but does not work generally with RGui 2.1.1 patched, Windows XP:

 > unback(x="n\o")
[1] "no"

	  I'm also unable to parse "echo", suggested by Ten Harding and
Henrik
Bengtsson:

 > echo D:/spencerg/statmtds/R/Rnews> tmp.txt
Error: syntax error
 > echo cat(gsub("\\\\", "/",
readLines("tmp.txt"))) | R --slave
Error: syntax error

	  Earlier today, Sundar Dorai-Raj helped me with the following:

 > (File0 <- file.choose())
[1]
"D:\\spencerg\\dataPOWER\\stats\\Tukey\\Boxplot_missing_Tukey2.txt"
 > strsplit(File0, "\\\\")
[[1]]
[1] "D:"                         "spencerg"
[3] "dataPOWER"                  "stats"
[5] "Tukey"                     
"Boxplot_missing_Tukey2.txt"

 > fp. <- strsplit(File0, "\\\\")[[1]]
 > (path <- paste(fp.[-length(fp.)], collapse="/"))
[1] "D:/spencerg/dataPOWER/stats/Tukey"
 > setwd(path)
 > getwd()
[1] "D:/spencerg/dataPOWER/stats/Tukey"
 > File <- fp.[length(fp.)]
 > File
[1] "Boxplot_missing_Tukey2.txt"

	  Thanks to everyone who has contributed (or even read) this thread. 
I'm confident that a better method exists.

	  Best Wishes,
	  Spencer Graves
	
David Duffy wrote:
> I couldn't resist adding a more literal answer
> 
> unback <- function(x) {
>   chars <- unlist(strsplit(deparse(x),""))
>   chars <- chars[-c(1,length(chars))]
>   paste(gsub("\\\\","/",chars),collapse="")
> }
> 
> unback("\n")
> 
> 
> | David Duffy (MBBS PhD)                                         ,-_|\
> | email: davidD at qimr.edu.au  ph: INT+61+7+3362-0217 fax: -0101  /     *
> | Epidemiology Unit, Queensland Institute of Medical Research   \_,-._/
> | 300 Herston Rd, Brisbane, Queensland 4029, Australia  GPG 4D0B994A v
> 
> ______________________________________________
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-- 
Spencer Graves, PhD
Senior Development Engineer
PDF Solutions, Inc.
333 West San Carlos Street Suite 700
San Jose, CA 95110, USA

spencer.graves at pdf.com
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Fax: 408-280-7915

On Wed, 29 Jun 2005, David Duffy wrote:
> I couldn't resist adding a more literal answer
This can only work for escapes which are preserved.  The parser maps
\n to a character (LF) and the deparser maps it back to \n.
This happens to be true of \a \b \f \n \r \t \v \\ but no others.

For example, \s is mapped to s, and there is no difference between \s and
s in the parsed input.
>
> unback <- function(x) {
>  chars <- unlist(strsplit(deparse(x),""))
>  chars <- chars[-c(1,length(chars))]
>  paste(gsub("\\\\","/",chars),collapse="")
> }
>
> unback("\n")
> unback("\s")
[1] "s"

Spencer Graves keeps on insisting there is a better way, but all the
solutions are to avoid sending the string to the parser, and hence
avoiding having the string directly in an R script.  This is common in 
shell scripts, which use 'here' documents to avoid 'quoting
hell'.

We can do that in R too. Here are two variants I have not seen in the 
thread

test1.R:
scan("", "", allowEscapes=FALSE, n=1, quiet=TRUE)
D:\spencerg\dataPOWER\stats\Tukey\Boxplot_missing_Tukey2.txt
catIx, "\n", sep="")

R --slave --vanilla < test1.R
D:\spencerg\dataPOWER\stats\Tukey\Boxplot_missing_Tukey2.txt

(This one does not allow quoted strings.)

test2.R:
x <- readLines(stdin(), n=1)
"D:\spencerg\dataPOWER\stats\Tukey\Boxplot_missing_Tukey2.txt"
x <- gsub('^"(.*)"$', "\\1", x)
cat(x, "\n")

R --slave --vanilla < test2.R
D:\spencerg\dataPOWER\stats\Tukey\Boxplot_missing_Tukey2.txt

(This one allows surrounding quotes or not.)

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595