Hi Rolf
I am not at all an expert in regex but
gsub("[[:alpha:]]","",x)
Works as you expected. Do not ask me why.
Cheers
Petr
> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Rolf
Turner
> Sent: Wednesday, August 23, 2017 7:46 AM
> To: r-help mailing list <r-help at r-project.org>
> Subject: [R] Flummoxed by gsub().
>
>
> I have a vector (say "x") of the form
>
> [1] "mung5" "mung10" "mung20"
"gorp5" "gorp10" "gorp20"
>
> I want to extract just the numbers (strings of digits) that appear at the
end of
> the strings in "x".
>
> My reading of ?regex led me to believe that
>
> gsub("[:alpha:]","",x)
>
> should give the result that I want. However it returns
>
> [1] "mung5" "mung10" "mung20"
"gor5" "gor10" "gor20"
>
> i.e. it chops the last letter out of the "gorp" string, but
nothing else.
>
> I am completely bewildered by this behaviour and can see no rationale for
it
> nor any way to adjust my syntax to get what I want.
>
> A bit of Googling led me to the information that
>
> gsub("\\D","",x)
>
> should work, and indeed it does, giving:
>
> [1] "5" "10" "20" "5"
"10" "20"
>
> OMMMMM! (Apparently "\D" means *not* a digit.)
>
> So I have *a* solution to my problem. However I would really like to know
why
> the <expletive deleted> the first idea I tried did not work and what
it is actually
> *doing*!
>
> Anybody?
>
> cheers,
>
> Rolf Turner
>
> --
> Technical Editor ANZJS
> Department of Statistics
> University of Auckland
> Phone: +64-9-373-7599 ext. 88276
>
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