'A rigorous way of dealing with some messy real-world data'

摘要

I think it's like the way we make and use road maps.If you have a map you can obviously trace individual journeys on it, you can plan them or choose between them. There's also a kind of reverse process as well -you can turn a set of journeys back into a map. So, if you know about lots of journeys that people have been on, described as a list of places, you can combine those back into an overall map. It might be fairly abstract and would look like a kind of network with lots of points and arrows joining them together, but it would still be a usable map. It becomes even more usable if you know how common each journey is. In effect, you mark on your map the motorways and the side roads, then you can start to say something about which routes people are most likely to take at each junction.