R help - Dec 2009 - how to replace a single backward slash with a double backward slash?

Dear R-helpers:

Hours ago, I asked how to replace a single forward slash with a double
backward slash and recieved great help. Thanks again for all the repliers.

In the meantime, I wonder how to replace a single backward slash with a
double backward slash?

e.g., I want change "c:\test" into "c:\\test"

I tried the following but does not work.
gsub("\\\","\\\\","c:\test")

Can someone help?

Thanks a lot in advance.

-Sean

	[[alternative HTML version deleted]]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Sean Zhang
> Sent: Sunday, December 13, 2009 2:11 PM
> To: r-help at r-project.org
> Subject: [R] how to replace a single backward slash with a 
> double backwardslash?
> 
> Dear R-helpers:
> 
> Hours ago, I asked how to replace a single forward slash with a double
> backward slash and recieved great help. Thanks again for all 
> the repliers.
> 
> In the meantime, I wonder how to replace a single backward 
> slash with a
> double backward slash?
> 
> e.g., I want change "c:\test" into "c:\\test"
> 
> I tried the following but does not work.
> gsub("\\\","\\\\","c:\test")
The input string "c:\test" contains no backslash
character, nor a "t" character.  It contains
   cee
   colon
   tab ("\t")
   ee
   ess
   tee
If you output the string using cat() you will see
the tab action and the missing "t".

"\t" means tab, "\n" newline, "\r" carriage
return,
"\52" octal 52 (asterisk in ASCII encoding), "\x2a"
hexadecimal 2a (also asterisk), etc.  ?Syntax may
give all the details.

If you want to change tabs to the 2-character sequences
backslash t, then do
  > gsub("\t", "\\\\t", "c:\test")
  [1] "c:\\test"
  > cat(.Last.value, "\n")
  c:\test

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 
> 
> Can someone help?
> 
> Thanks a lot in advance.
> 
> -Sean
> 
> 	[[alternative HTML version deleted]]
> 
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> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
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>

On Dec 13, 2009, at 5:11 PM, Sean Zhang wrote:
> Dear R-helpers:
>
> Hours ago, I asked how to replace a single forward slash with a double
> backward slash and recieved great help. Thanks again for all the  
> repliers.
>
> In the meantime, I wonder how to replace a single backward slash  
> with a
> double backward slash?
>
> e.g., I want change "c:\test" into "c:\\test"
>
> I tried the following but does not work.
> gsub("\\\","\\\\",)
>
> Can someone help?
Your problem may be that you think there actually is a "\" in "c:
\test". There isn't:

 > grep("\\\\", "c:\test")  # which would have found a
true "\"
integer(0)

It's an escaped "t", which is the tab character = "\t":

 > grep("\\\t", "c:\test")
[1] 1
 > cat("rr\tqq")
rr	qq

If your goal is to make file paths in Windows correctly, then you have  
two choices:

a) use doubled "\\"'s in the literal strings you type, or ...
b) use "/"'s

So maybe you should explain what you are doing? We don't request that  
background out of nosiness, but rather so we can give better answers

-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT