I have a detailed map matrix in R (x,y,z co-ords), and am wishing to calculate the physical gradient at a number of points on the map wrt different axes and averaged over a number of distances (i.e. slope in N-S direction averaged over 10m, 50m, 100m respectively). Is there any function within R which will allow for this? Thanks, Laura Laura Quinn Institute of Atmospheric Science School of Earth and Environment University of Leeds Leeds LS2 9JT tel: +44 113 343 1596 fax: +44 113 343 6716 mail: laura at env.leeds.ac.uk