I have two datasets, big and small. s_date<-c(2005-12-02, 2005-12-01, 2004-11-02,2002-10-05,2000-12-15) s_id<-c(a,a,b,c,d)
b_date<- c(2005-12-31, 2005-12-31, 2004-12-31,2002-10-05,2001-10-31,1999-12-31) b_id<-c(a,b,c,d,e,c) small<-data.frame(date_=as.Date(s_date),id=s_id) big<-data.frame(date_=as.Date(b_date),id=b_id) For each row in big, I want to look for a match in small where two conditions are met: a. big$id=small$id b. big$date_>=small$date If match is found, I wish to return the value of the date. If no match is found, I want NA. If more than 1 match is found, I wish to return the match where small$date is greatest. Im thinking I might be able to do this using the match function, and by sorting the small dataset by date_ in descending order. However, I do not know how to make the match conditional on big$date_>=small$date_. Any help is appreciated. ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
