[R] : regular expressions: escaping a dot

[Tobias Verbeke]

Wolfram Fischer wrote:

> What's really the problem with:
> 
>> regexpr( '\.odt$', "xxxxYodt", perl=TRUE )
> 	Warning: '\.' is an unrecognized escape in a character string
> 	Warning: unrecognized escape removed from "\.odt$"
> 	[1] 5
> 	attr(,"match.length")
> 	[1] 4
> 
> I know that I could use:
>> regexpr( '[.]odt$', "xxxxYodt", perl=TRUE )
> 
> But it seems to me that the first expression is also
> an accepted regular expression in accordance with perl.

In R you have to escape the "\".

 From the help page of regexpr:

## Double all 'a' or 'b's;  "\" must be escaped, i.e., 'doubled'
gsub("([ab])", "\\1_\\1_", "abc and ABC")

HTH,
Tobias

-- 

Tobias Verbeke - Consultant
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