I have added the "sum" calculation (find the updated source code
in CVS).
One thing it is missing is "n" for number of sites in the sample.
You don't get very far trying to do any follow on stats without n ..
The man page claims it does, but I don't see the option..
I guess the user could do sum/mean if they had to.
"s.cellstats calculates univariate statistics of sites lists for each
cluster of input sites falling within each cell of the current region.
This includes the number of sites, ..."
cheers,
Hamish