The saddest part of all this is that the author of the overfitted example is clearly a bright, bright guy as based on his Stack Overflow profile - top 12%, better than me certainly but there's no obvious way to contact him and no comments on his blog so, sigh…
My next stopping point on this d3 quest was Greg Park's Adding a Live D3 Visualization to Rails. This is a lot more complex than Overfitted but all the bits are there and there's a full repo. So the first step was a quick fork so I could remove the postgres dependency. An install showed that everything worked in Rails 4. The moment of truth was to try it in Rails 5 – and it worked brilliantly! Thank you Greg!
- take my rails 5 exmaple
- make a branch
- update gemfile and add d3-rails
- bundle install
- try the app and see if the graphs display