Jan Dennison

d3.js Directional Force Map

Interactive train map using d3.js Force

July 2015

GitHub Repo Live Demo

Design, HTML, CSS, d3.js

Remote Island Train Map

d3 Directional-Force Map


  • I had previously worked with d3 for simple plot graphs, pie charts, bar charts
  • Had never worked with more advanced d3 implementations, including force charts
  • Had not worked with SVG markers, defs, or hover effects


  • Was familiar with how d3 uses data to generate coordinates, so basic line-node graph was completed within 2-3 hours
  • Refactored provided data into array of cities and a way to populate nodes and reference links for much cleaner and easier to read code
  • Spent about 4 hours learning and attempting arrowhead markers on lines, and associating labels with them
    • Eventually refactored code to first generate svg groups that hold line and marker so that the fill/stroke colors could match
  • Spent (mumble) hours on attempting shortest path implementation, reading about Dijkstra's algorithm, and experimenting with online d3 dijkstra examples
    • Was unable to get shortest paths working

Lessons Learned

d3 Force


  • SVG markers do not inherit line color. Refactored code generating connection lines as groups holding the line and marker to manipulate highlight color effect.
  • Leveraged these groups to add line titles as hover tooltips showing distances
  • Some resources used include:

Shortest Path

  • Spent most of my time down a rabbit hole reading source code and attempting this stretch goal
  • Was unable to crack Dijkstra's algorithm or get various examples online working with my implementation
  • Some references used:

Background image via unsplash