R-help,
Sorry if this is more of a regex question than an R question. However,
help would be appreciated on my use of the regexpr function.
In the first example below, I ask for all characters (a-z) in 'abc123';
regexpr returns a 3-character match beginning at the first character.
> regexpr("[[:alpha:]]*", "abc123")
[1] 1
attr(,"match.length")
[1] 3
However, when the text is flipped regexpr, and I ask for a match of all
characters in '123abc', regexpr returns a zero-character match beginning
at the first character. Can someone explain what a zero length match
means (i.e. why not return -1), and why the result isn't 4,
match.length=3?
> regexpr("[[:alpha:]]*", "123abc")
[1] 1
attr(,"match.length")
[1] 0
Thanks, Robert
> R.version
_
platform x86_64-apple-darwin9.8.0
arch x86_64
os darwin9.8.0
system x86_64, darwin9.8.0
status Patched
major 2
minor 11.0
year 2010
month 05
day 11
svn rev 51984
language R
version.string R version 2.11.0 Patched (2010-05-11 r51984)
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
