[R] Wildcard for indexing?

[Johannes Radinger]

-------- Original-Nachricht --------
> Datum: Tue, 14 Feb 2012 10:18:33 -0500
> Von: Sarah Goslee <sarah.goslee at gmail.com>
> An: Johannes Radinger <JRadinger at gmx.at>
> CC: R-help at r-project.org
> Betreff: Re: [R] Wildcard for indexing?

> Hi,
> 
> You should probably do a bit of reading about regular expressions, but
> here's one way:
> 
> On Tue, Feb 14, 2012 at 10:10 AM, Johannes Radinger <JRadinger at gmx.at>
> wrote:
> > Hi,
> >
> > -------- Original-Nachricht --------
> >> Datum: Tue, 14 Feb 2012 09:59:39 -0500
> >> Von: "R. Michael Weylandt" <michael.weylandt at gmail.com>
> >> An: Johannes Radinger <JRadinger at gmx.at>
> >> CC: R-help at r-project.org
> >> Betreff: Re: [R] Wildcard for indexing?
> >
> >> I think the grep()-family (regular expressions) will be the easiest
> >> way to do this, though it sounds like you might prefer grepl() which
> >> returns a logical vector:
> >>
> >> ^[AB] # Starts with either an A or a B
> >> ^A_ # Starting with A_
> >>
> >> a <-  c("A_A","A_B","C_A","BB","A_Asd"
> >> grepl("^[AB]", a)
> >> grepl("^A_")
> >
> > Yes grepl() is what I am looking for.
> > is there also something like an OR statement e.g. if I want to
> > select for elements that start with "as" OR "df"?
> 
> > a <- c("as1", "bb", "as2", "cc", "df", "aa", "dd", "sdf")
> > grepl("^as|^df", a)
> [1]  TRUE FALSE  TRUE FALSE  TRUE FALSE FALSE FALSE
> 
> 
> The square brackets match any of those characters, so are good
> for single characters. For more complex patterns, | is the or symbol.
> ^ marks the beginning.

Thank you so much Sarah! I tried that | symbol intuitively, there was just a problem with the quotation marks :(

Now everything is solved...

/johannes

> 
> Sarah
> 
> -- 
> Sarah Goslee
> http://www.functionaldiversity.org

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