We take a shot at that question over at Scatterplot.

The Co-Assignment Galaxy represents titles based on the extent to which they appear together on syllabi.  Each title is a dot whose size is determined by the title’s total assignment count in the collection.  This simple principle structures a very detailed map of fields, subfields, and their boundaries.  It also combines what we could call content-based and institutional ways of thinking about fields.  By content based, I mean that the layout is derived solely from similarities in the assigned contents of millions of classes, with no a priori knowledge about how those classes divide into sociology or history or physics (we added the labels later).  At the same time, we developed tools that do sort syllabi into the classificatory schemas used by universities, which reflect a more administrative and institutional view of fields. This institutional account shows up in the graph through the use of color.  A title receives a color based on its predominant field of assignment. Field boundaries and border zones are represented in the Galaxy by this interaction between spatial layout and color.