Spatial grid

Ogbos Okike <ogbos.okike at gmail.com> writes:

My global lightning data is just two columns labeled latitude
and longitude. Using library(maps), I plotted the world map and plotted
latitude and latitude as points. However, the frequency of lightning
occurrence and hence the points is so high that the plot looks more or less
like a blurred image, and makes it impossible for me to compare the
lightning flash density of the regions of the earth.

Probably what you want to do is to compute a kernel smoothed density (or intensity) estimate on the sphere. The density or intensity will give you the number of strikes per unit area on the sphere, measured locally. This can be plotted as a colour image where 'hot' colours mean higher densities of lightning.  

You can do this with the function sm.sphere() in the 'sm' package, for example. 

Adrian Baddeley