Hi,Yiannakoulias You may use proc sql.

proc sql noprint; create table result as select * from t group by id having max(valuen)=valuen; quit;

Regards,William

"N Yiannakoulias" <nwy@srv.ualberta.ca> wrote in message news:aghjt9$9q4$1@pulp.srv.ualberta.ca... > Hi all, > > I have a large data set which represents a 2 dimensional > grid over a geographic area. I've built an adjacency > file of this grid that looks like this: > > ID NID ValueN > 1 2 65 > 1 6 26 > 2 1 26 > 2 3 30 > 2 7 2 > 3 2 65 > 3 4 34 > 3 8 88 > and so on... > > ID is an identifier for each grid > NID is a neighbour's ID > ValueN is a value associated with a neighbour > > Now, I want to group adjacent records such that starting > with area 1 (represented by ID=1) the adjacent area with > the largest ValueN is grouped with this area (ID=1). > Once a neighbour is grouped, it can no longer be a part > of any other group. _This is where I get stuck_. For > example, NID=2 meets the condition for area 1. As a > result, records with NID=2 AND ID=2 should be removed > from the dataset as I proceed with grouping. I haven't > been able to do this successfully. Can anyone offer > any advice? It seems pretty trivial, but maybe it isn't? > > N >