Hi, I've been trying to learn and use R for data analysis, and so far it has be OK. It is very slow with the aov command. But, other than that things are generally OK. Anyway, todays problem is one that I have looked in quite a few places to try to solve but to know avail. I hope the list can help. I have my data organized in the appropriate way (i.e. a data point on each row and columns for each variable). I want to divide my subjects up by a median. However, I don't want the overall subject median but a subset, and then to split the entire subjects data on that subset. I don't see a way to do that at all. Any help would be appreciated. to make things clearer, here is an example of how to split subject by median ss<-split(s, ave(s$x, s$subj) > median(ave(s$x,s$subj))) what I need to do is split by subject when s is further split by a sub factor. TIA John Christie