[R] grep with "|" character

[Prof Brian Ripley]

Easier is

grep("|", stringvector, extended = FALSE)

The only reason for having basic regexps in R is to avoid some of the 
escaping needed.

On Tue, 23 Oct 2007, Duncan Murdoch wrote:

> On 23/10/2007 6:34 AM, Daniel Brewer wrote:
>> Hi,
>>
>> I am having a problem searching for the "|" character in a string.
>>
>>> grep("|",stringvector)
>> Gives all the strings in a vector but when I try to escape it
>>> grep("\|",stringvector)
>> It comes up with the error
>> Warning messages:
>> 1: '\|' is an unrecognized escape in a character string
>> 2: unrecognized escape removed from "\|"
>>
>>
>> Anyone know how to solve this?
>
> Grep needs to see the escape character, so you need to escape that too,
> i.e. use
>
>
> grep("\\|",stringvector)
>
> The \\ is the way to enter a single backslash in an R string.  The
> vertical bar isn't special to R, so it doesn't need escaping at that level.
>
> Duncan Murdoch
>
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>

-- 
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)
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