[R] grep with search terms defined by a variable

[Joshua Wiley]

Hi Daniel,

What about this?

#############
my.names <- c("Emil Jannings", "Charles Chaplin",
              "Katherine Hepburn", "Meryl Streep")
search.term <- c("Emil", "Meryl")

for(i in 1:length(search.term)){
    print(grep(paste("^", search.term, sep="")[i], my.names))
  }
##############

Cheers,

Josh

On Mon, Aug 2, 2010 at 9:05 PM, Daniel Malter <daniel at umd.edu> wrote:
>
> Hi, I have a good grasp of grep() and gsub() for finding and extracting
> character strings. However, I cannot figure out how to use a search term
> that is stored in a variable when the search string is more complex.
>
> #Say I have a string, and want to know whether the last name "Jannings" is
> in the string. This is done by
>
> names=c("Emil Jannings")
> grep("Emil",names)
>
> #Yet, I need to store the search terms in a variable, which works for the
> very simple example
>
> search.term="Emil"
> grep(search.term,names)
>
> #but I cannot get it to work for the more difficult example in which I want
> to do something like
>
> grep(^search.term,names)
> grep("^search.term",names)
> grep("^"search.term,names)
>
> #Implying that the search term must be the first part of the string that is
> being searched
>
> #Ultimately, I need to to loop over several strings stored in search.term,
> for example,
>
> names=c("Emil Jannings","Charles Chaplin","Katherine Hepburn","Meryl
> Streep")
> search.term=c("Emil","Meryl")
>
> for(i in 1:length(names)){
>     print(grep(^search.term[i],names))
> }
>
> So the questions I have are two. 1. How do I concatenate terms that I would
> normally quote (like "^") with variables that contain search terms and that
> normally would not be quoted? 2. How do I run this over indices of the
> variable that contains the search terms?
>
> I greatly appreciate any help,
> Daniel
>
>
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/grep-with-search-terms-defined-by-a-variable-tp2311294p2311294.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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.
>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/