I have two questions related to calculating a spatial weights matrix. First, I have a basic county data set and I want to use a FIPS (5-digit state and county) as the unique identifier instead of the object ID, but the SWM tool says that the FIPS variable is not a valid unique identifier. Any suggestions about how to resolve this?
Second, ultimately I want to create a SWM among counties based on sharing watersheds. I have a contiguous watershed shapefile. So, for a given county I can find all the watersheds that it intersects and then find the counties that intersect those watersheds. But I want to do this for each county and create a SWM therefrom for the contiguous US. Any suggestions would be greatly appreciated.