[R] Wildcard for indexing?

[Johannes Radinger]

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"?

/johannes

> 
> Michael
> 
> On Tue, Feb 14, 2012 at 9:54 AM, Johannes Radinger <JRadinger at gmx.at>
> wrote:
> > Hi,
> >
> > I'd like to know if it is possible to use wildcards * for indexing...
> > E.g. I have a vector of strings. Now I'd like to select all elements
> > which start with A_*? I'd also need to combine that with logical
> operators:
> >
> > "Select all elements of a vector that start with A (A*) OR that start
> with B (B*)"
> >
> > Probably that is quite easy. I looked into grep() which I think might
> perform such tasks, but probably there is a more straigth forward solution.
> >
> > a <- c("A_A","A_B","C_A","BB","A_Asd")
> > a[a=="A_A"| a=="A_B"] # here I'd like an index but with wildcard
> >
> > /johannes
> > --
> >
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