Here are the grisly details about calculating adjusted defensive impact by court location that nobody has been waiting for. I’ve partially explained the methods before here, but some things have changed and that explanation was not comprehensive. So buckle in and get ready for a lot of really dry prose, a couple of kinda cool graphs, and some code that should help you understand the algorithm I’m using to select shots.
Thanks everyone for the really great response to my previous blog on twitter. Some people asked good questions and I want to clarify a few things and talk about some improvements that could (maybe should) be made to this. This post will be kinda methods-y but may include some non-technical tidbits.
This is just a catch-all post about methods that I will reference in the future when I post a graph or a regression or whatever. My plan is to update this every time I add something new that I think requires further explanation. So without further ado…
From here on out, the way I do the shot-chart visualizations should be fairly stable. There are really only a couple of things that need explanation here. Data is usually current as of the date of the blog post but does not update automatically, so backdate appropriately. All shots taken against a team or by a player or whatever it is are grouped into 1ft x 1ft squares that cover the court. 2 and 3 point shots are not mixed in this process. Basically if a square’s center is inside the arc, it should contain only 2pt shots, and if the square’s center is outside the arc it should contain only 3pt shots.