Greetings,
The following question has come up in an off-list discussion.
Is it possible to construct a regular expression 'rex' out of
two given regular expressions 'rex1' and 'rex2', such that a
character string X matches 'rex' if and only if X matches 'rex1'
AND X does not match 'rex2'?
The
I think you have missed grepl(), e.g.
X[grepl(rex1, X) !grepl(rex2, X)]
grepl is a fairly recent addition (2.9.0) that is used extensively in
R's own text-processing operations (e.g. help files, utilities such as
'R CMD check').
On Sat, 12 Jun 2010, ted.hard...@manchester.ac.uk wrote:
Thanks, Brian. I had indeed overlooked grepl() (too busy delving
into the syntax summary)! That is certainly a useful shortcut of
the construction I had used.
Your Not in general implies that using grep() twice (in this example;
more times in more complex combinations) is inevitable -- which of
On Sat, Jun 12, 2010 at 5:38 AM, Ted Harding
ted.hard...@manchester.ac.uk wrote:
Greetings,
The following question has come up in an off-list discussion.
Is it possible to construct a regular expression 'rex' out of
two given regular expressions 'rex1' and 'rex2', such that a
character string
Thanks, Gabor, for the initiation to perly regexps! I've only
been used to extended ones till now. A pity, perhaps, that
perl=TRUE is not an option for the likes of browseEnv(),
help.search(), list.files() and ls() (which take extended regexps),
but one can always assign the output and then
5 matches
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