[R-sig-Geo] GRID based calculations

[Fatih Kara]

Hi,

We are developing a grid based database which provides several types of data. One of the layers in this database will be land cover data with 30 land cover types. Our grids will cover almost 90 pixels and our purpose is that if someone click on the grid, percentage of land cover types should be seen automatically like 20% forest, 30% water, and 50% grass.
 
What should we do? Is there any related code samples? 

Thanks
-- 
Fatih Kara