[R] regular expressions : extracting numbers

[Gabor Grothendieck]

I assume if you want the "" components to be NA then you really intend
the result to be a numeric vector.  The following replaces all non-digits
with "" (thereby removing them) and then uses as.numeric to convert the
result to numeric.  Just omit the conversion if you want a character
vector result:

s <- c("lema, rb 2%", "rb 2%", "rb 3%", "rb 4%", "rb 3%", "rb 2%,mineuse",
   "rb", "rb", "rb 12", "rb", "rj 30%", "rb", "rb", "rb 25%", "rb", "rb",
   "rb", "rj, rb")

as.numeric(gsub("[^[:digit:]]+", "", s))

On 7/30/07, GOUACHE David <D.GOUACHE at arvalisinstitutduvegetal.fr> wrote:
> Hello all,
>
> I have a vector of character strings, in which I have letters, numbers, and symbols. What I wish to do is obtain a vector of the same length with just the numbers.
> A quick example -
>
> extract of the original vector :
> "lema, rb 2%" "rb 2%" "rb 3%" "rb 4%" "rb 3%" "rb 2%,mineuse" "rb" "rb" "rb 12" "rb" "rj 30%" "rb" "rb" "rb 25%" "rb" "rb" "rb" "rj, rb"
>
> and the type of thing I wish to end up with :
> "2" "2" "3" "4" "3" "2" "" "" "12" "" "30" "" "" "25" "" "" "" ""
>
> or, instead of "", NA would be acceptable (actually it would almost be better for me)
>
> Anyways, I've been battling with gsub() and things of the sort, but I'm drowning in the regular expressions, despite a few hours of looking at Perl tutorials...
> So if anyone can help me out, it would be greatly appreciated!!
>
> In advance, thanks very much.
>
> David Gouache
> Arvalis - Institut du Végétal
> Station de La Minière
> 78280 Guyancourt
> Tel: 01.30.12.96.22 / Port: 06.86.08.94.32
>
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