5 messages · wolfram at fischer-zim.ch, Tobias Verbeke, Peter Dalgaard +1 more
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$', "xxxxYodt", perl=TRUE )
But it seems to me that the first expression is also an accepted regular expression in accordance with perl. Regards - Wolfram
What's really the problem with:
regexpr( '\.odt$', "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 Business & Decision Benelux Rue de la r?volution 8 1000 Brussels - BELGIUM +32 499 36 33 15 tobias.verbeke at businessdecision.com
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.
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 ....
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
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...)
O__ ---- Peter Dalgaard ?ster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
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