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 grep(
On Sat, Jun 12, 2010 at 5:38 AM, Ted Harding
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 X matches 'rex' if and
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
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:
Gr
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