[ml_thoughts]

A problem that I was surprised to not be solved well is the study of paths (not represented as graphs). It seems that for example trying to cluster trajectories over time through real coordinates has a bit of prior work (there’s a bit of an unintuitive and costly metric called the Frechet distance that can be used) but is not the solved problem I would have expected for this type of fundamental problem (that would seem to come up a lot for human movement applications). Like answering the question of “what are the most commonly used paths to get to work” without resorting to discretizing steps into nodes on a graph seems tricky as far as I can tell.