Daniel, If you want to search for each term at the beginning of a sting, using the regular expression construct '^', you might use the following
> search.terms <- c("Emil", "Meryl") > names <- c("Emil Jannings", + "Charles Chaplin", + "Katherine Hepburn", + "Meryl Streep") > for(term in search.terms) { + print(grep(paste("^",term,sep=""),names)) + } [1] 1 [1] 4 -Matt On Tue, 2010-08-03 at 00:05 -0400, Daniel Malter 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 > > > > -- Matthew S. Shotwell Graduate Student Division of Biostatistics and Epidemiology Medical University of South Carolina ______________________________________________ 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.