In one of my research projects we have a set of points on a two dimensional plane that when given a single point from that set we want to be able to know who its "neighbors" are. For our work we have the mesonet stations spread across the state of Okalhoma and we want to be able to select the neighboring stations. There are a couple of methods that are intuitive but require setting a parameter, something I'm not fond of. Also we have the concept of multiple levels of neighbors, so my first neighbors, my second neighbors and so on.