I have been spending some time learning d3.js (Data-Driven Documents), a data visualisation library for javascript. I used d3 to create a bubble chart of all programming languages I have used throughout my public GitHub repositories, using data from the GitHub API.


I added a function to my site’s custom build plugin to output the language statistics to a json file. It uses octokit to interact with GitHub and the JEKYLL_GITHUB_TOKEN I had previously configured for the github-metadata plugin.

    def _get_repo_languages(site)
        client = Octokit::Client.new({:auto_paginate => true, :access_token => ENV['JEKYLL_GITHUB_TOKEN']})

        language_totals = Hash.new
        client.list_repos.each do |repo|
            languages = client.languages(repo['full_name'])
            language_totals.merge!(languages.to_h) {|k, new, old| new + old}

        # Write json file in the format: {"language_name": total_bytes, "C": 4567, ...}
        File.open('data/language-totals.json', 'w') do |f|

This approach does of course mean that I have to manually perform a rebuild of my site locally to update the data. I also made the data update an optional part of the build process to avoid hitting the GitHub API and slowing down the build each time a rebuild is triggered.


I used d3’s circle packing algorithm (d3.packSiblings), which packs circles based on their radii. To calculate the radii corresponding to each language I used the following formula:

This is to prevent individual bubbles from becoming too large or small.

The bubbles are then displayed in an SVG using the following:

d3.json("/data/language-totals.json", function (error, data) {
    if (error) throw error;

    // Add groups for each bubble
    var nodes = svg.selectAll('.bubble')
        .attr('class', 'bubble')
        .attr('transform', function (d){
            return "translate(" + d.x  + "," + d.y + ")"; 

    // Add the circle elements
        .attr("r", function (d) { return d.r; })
        .style("fill", function (d) { return d.color })
        .style("stroke", "white")
        .style("stroke-width", 2);

    // Add the circle text
        .attr("dy", ".3em")
        .style("text-anchor", "middle")
        .text(function (d) { return d.name + " " + d.percentage.toPrecision(3) + "%"; })
        // Hide text for small bubbles to avoid overlaps
        .classed("hide", function (d) { return (this.getBBox().width > (2.5 * d.r)); });

The full source is available in this site’s repository.

Languages Used in my Public Repos

View Standalone.

Note: Mouse hovering doesn’t currently work correctly in IE due to this bug.