Hi, there: I have a syntax question. I have a dataset x with 100 variables. I did not set the column name so I used x$V1...x$V100. For my case, I need to put the number (e.g. 20) into another variable, like index so that I can refer to x$V20 by using something like x$V(index) but I don't know how to do that in R. thanks, Ed