I have a a bunch of polygons representing different ecological niches (combinations of soil and climate type). For each point p in the map , I want to know how much of each niche X is within 2000km (call this value a(X,p) ) and whether the niche is present or not within 100 (call this b(X,p)) . I would like to create a raster where each point's value is equal to
SUM OVER ALL X of ( a(X,p)*b(X,p) )
the idea is: if a plant is able to live in point p, how likely is it to be able to colonize other ecosystems further away?
Keep in mind that I have about 700 ecosystems so I can't do this by hand.