I found Plotly’s capability to be a bit lacking, so I spend another couple hours updating the map. Since creating the original data set, more alums have chimed in, so they’ve been included.
I have a new version written in Leaflet for R. This package is just as easy to use as Plotly, but with more options.
Peter Lee (2013) pointed me to CartoDB and I got my first proptype working there in 5 minutes, but it didn’t have enough control. It looks like the underlying Leaflet package drives CartoDB.
Ideally, there would be a slider for years. For now, each year is in its own group.continue / comment