[R] : regular expressions: escaping a dot

[Prof Brian Ripley]

On Thu, 28 Jun 2007, Peter Dalgaard wrote:

> Prof Brian Ripley wrote:
>>
>>
>> This is explained in ?regexp (in the See Also of ?regexpr):
>>
>>       Patterns are described here as they would be printed by 'cat': _do
>>       remember that backslashes need to be doubled when entering R
>>       character strings from the keyboard_.
>>
>> and in the R FAQ and ....
>>
>>
> Hmm, that's not actually correct, is it? Perhaps this is better
>
> "...entering R character string literals (i.e., between quote symbols.)"
>
> The counterexample would be
>
>> readLines()
> \\abc
> [1] "\\\\abc"
>
> (of course it is more important to get people to read the documentation
> at all...)

The definition of 'character string' used throughout the help is your 
'character string literal', as distinct from an element of a character 
vector.

-- 
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