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 <[email protected]> wrote: > Hi, > > -------- Original-Nachricht -------- >> Datum: Tue, 14 Feb 2012 09:59:39 -0500 >> Von: "R. Michael Weylandt" <[email protected]> >> An: Johannes Radinger <[email protected]> >> CC: [email protected] >> 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. Sarah -- Sarah Goslee http://www.functionaldiversity.org ______________________________________________ [email protected] 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.
