I guess this is trivial, I apologize, I couldn't find how to do it. I am trying to abstain from a loop, so I am trying to vectorize the process: I need to do something like grep, but where the pattern is a vector. Another option is a match, where the value is not only the first location. For example data (which is not how the real data is, otherswise I would exploit it structure): COUNTRIES=c("Austria","Belgium","Denmark","France","Germany", "Ireland","Italy","Luxembourg","Netherlands", "Portugal","Sweden","Spain","Finland","United Kingdom") COUNTRIES_Target=rep(COUNTRIES,times=4066) COUNTRIES_Origin=rep(COUNTRIES,each=4066) Now, currently I got a loop that: var_pointer=list() for (i in 1:length(COUNTRIES_Origin)) { var_pointer[[i]]=which(COUNTRIES_Origin[i]==COUNTRS_Target) } The problem with match is that match(x=COUNTRIES_Origin,table=COUNTRIES_Target) returns a vector of the same length as COUNTRIES_Origin and the value is the first match, while I need all of them. The issue with grep is that grep(pattern=COUNTRIES_Origin,x=COUNTRIES_Target) is the given warning: Warning message: In grep(pattern = COUNTRIES_Origin, x = COUNTRIES_Target) : argument 'pattern' has length > 1 and only the first element will be used Any suggestions?