[R-sig-Geo] Optimized search routine

[dooher1 at llnl.gov]

I am looking at different population density routines, running 
cumulative populations within a certain radial distance (as well as 
other type functions).  Is there a way to optimize the search, ie, 
setting up something like ESRI's SDE (which is basically a database 
that relates nearby grids to one another to optimize search routines 
and other queries?
Brendan