I have an interesting question:
Is there a dataset by which I can use to test whether two countries are adjacent? For example, if inputs are Mexico and U.S., they are adjacent; if inputs are England and Russia, they are not. Is it easy to produce an adjacency matrix for all the countries?
Edited: This question might be extended as, if we get a political boundary map, is there any ways to produce an adjacency matrix for all the political entities (e.g. Given a map of Florida, can a counties matrix be built to indicate the adjacency of all the counties)