[R-sig-Geo] Lightning density map

[Bogdan Antonescu]

Hi ,

I am trying to plot a cloud-to-ground lightning density map for Romania. 
The data set contains: date(year/month/dat), time(hh/mm/ss), latitude, 
and longitude for each lightning flash. The density maps were based on 
dividing the study area into a grid cells (e.g., 20-km to correspond 
with the audible range of thunder). I have used ArcGIS to calculate a 
density value for each cell by counting the number of lightning flashes 
within the cell and dividing by the cell area. The density value 
(flashes km−2) is then assigned to each cell.

Can someone help me on how to do this in R?

Thank you very much,

Bogdan