hi @johnburnmurdoch just one notice, but since the d3@6 newest release your amazing notebook is broken . I recommend pinning d3 modules versions on your require for instance if you do d3-selection@1  makes your notebook back to work again!

Radamés Ajna

I've sent a suggestion with 
> d3 = require('d3-scale@2','d3-array@1','d3-fetch@1','d3-selection@1','d3-timer@1','d3-color@1','d3-format@1','d3-ease@1','d3-interpolate@2','d3-axis@2', 'd3-geo@1', 'd3-selection-multi@1');