R help - Jun 2009 - negation in grep

Does anybody know how to negate a string in a grep command, i.e., 
what I need is to return only strings that do NOT contain a second 
string anywhere in the entire string.


for

txt <-
c("boo","goo","doob","foo","boofoo")

I need a grep command that returns strings with "oo" except when
"b"
is present anywhere. I know that

grep("[^b]oo" would work to exclude "boo" and
"boofoo" but not "doob"

So, what I need is

grep("oo + some syntax", txt)

should return

goo doo foo

I have tried

  grep("oo!boo",txt)

but it returns character(0).

any suggestions are much appreciated!

S.
-- 
Steven Orzack

You can try somthing about like this:

setdiff(txt, grep("(oob|boo|\\w[^oo]\\w)", txt, value = TRUE))


On Mon, Jun 22, 2009 at 6:45 PM, orzack <orzack@freshpond.org> wrote:
> Does anybody know how to negate a string in a grep command, i.e., what I
> need is to return only strings that do NOT contain a second string anywhere
> in the entire string.
>
>
> for
>
> txt <-
c("boo","goo","doob","foo","boofoo")
>
> I need a grep command that returns strings with "oo" except when
"b" is
> present anywhere. I know that
>
> grep("[^b]oo" would work to exclude "boo" and
"boofoo" but not "doob"
>
> So, what I need is
>
> grep("oo + some syntax", txt)
>
> should return
>
> goo doo foo
>
> I have tried
>
>  grep("oo!boo",txt)
>
> but it returns character(0).
>
> any suggestions are much appreciated!
>
> S.
> --
> Steven Orzack
>
> ______________________________________________
> 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.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

	[[alternative HTML version deleted]]

Try

  txt[- grepl(pattern, txt)]

  txt[! grepl(pattern, txt)]


On Mon, Jun 22, 2009 at 5:45 PM, orzack<orzack at freshpond.org>
wrote:
> Does anybody know how to negate a string in a grep command, i.e., what I
> need is to return only strings that do NOT contain a second string anywhere
> in the entire string.
>
>
> for
>
> txt <-
c("boo","goo","doob","foo","boofoo")
>
> I need a grep command that returns strings with "oo" except when
"b" is
> present anywhere. I know that
>
> grep("[^b]oo" would work to exclude "boo" and
"boofoo" but not "doob"
>
> So, what I need is
>
> grep("oo + some syntax", txt)
>
> should return
>
> goo doo foo
>
> I have tried
>
> ?grep("oo!boo",txt)
>
> but it returns character(0).
>
> any suggestions are much appreciated!
>
> S.
> --
> Steven Orzack
>
> ______________________________________________
> R-help at 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.
>