[R] regex problems with the escape character

[Gabor Grothendieck]

s1 should use \\ like this:

s1<- "C:\\Rtools\\bin;C:\\Rtools\\perl\\bin;C:\\Rtools\\MinGW\\bin;C:\\Program\\MiKTeX
2.7\\miktex\bin"

Also 1. you won't need to change your path in the first place if you use
the batchfiles at http://batchfiles.googlecode.com
2. there is also a free path editor discussed there. See Q4 or Q8
in the troubleshooting faq on that same page.

On Mon, Aug 17, 2009 at 3:21 AM, ravi<rv15i at yahoo.se> wrote:
> Hi R-users and R-experts,
> I am having a hard time in figuring out how to tackle regex questions where the "backslash" character is an integral part of the string. Let me explain how I came across this problem :
> I wanted to clearly see all the components in the windows environmental path variable. This is a long string. For easy readability, I wanted to split up this string so that each component starts on a new line. But I ran smack into a problem in the very first step - in reading in the string. Look at the following code :
>
> ##### path variable has been shortened to show only the first few components
> s1<- "C:\Rtools\bin;C:\Rtools\perl\bin;C:\Rtools\MinGW\bin;C:\Program\MiKTeX 2.7\miktex\bin;"
> s2<-gsub(";",";\n",s1)
> cat(s2,"\n")
>
> I get the following warning messages after the first line :
> Warning messages:
> 1: '\R' is an unrecognized escape in a character string
> 2: '\R' is an unrecognized escape in a character string
> 3: '\p' is an unrecognized escape in a character string
> 4: '\R' is an unrecognized escape in a character string
> 5: '\M' is an unrecognized escape in a character string
> 6: '\P' is an unrecognized escape in a character string
> 7: '\M' is an unrecognized escape in a character string
> 8: '\m' is an unrecognized escape in a character string
> 9: unrecognized escapes removed from "C:\Rtools\bin;C:\Rtools\perl\bin;C:\Rtools\MinGW\bin;C:\Program\MiKTeX 2.7\miktex\bin;"
>
> I thought about attempting to escape the escape character and so on. Is that a workable option here? However, for this to work, I must first be able to read in the string correctly. The simplest solution, if it is at all possible, would be to temporarily change the escape character. To "%", for example. Is such a declaration possible? Other alternatives?
> I would appreciate help in understanding different ways of solving this problem.
> Thanking you,
> Ravi
>
>
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