> I would like to know if it?s possible to create an index for a > variable/vector that specifies the value in the n position before > the actual value. > > For example, if X <- c(letters[1:10]), x[10] is ?j?. I would like to > create an index exp3 (the third position before) such as if z <- > x[exp3], then z[10] = ?g?.
x<- letters[1:10] Then either z<- c(rep(NA,3), x) z[10] #"g" or exp3<- 1:length(x) - 3; exp3[exp3<=0] <- NA z <- x[exp3] z[10] #"g" Regards, Richie. Mathematical Sciences Unit HSL ------------------------------------------------------------------------ ATTENTION: This message contains privileged and confidential inform...{{dropped:21}} ______________________________________________ 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.