title: Data aggregate/list with d3.js
body: <p>I'm a new d3.js user and I struggle to make a basic data conversion.</p>
  
  <p>I would like to move from this format...</p>
  
  <pre><code>[
    ["enduser-type","supplier","A","Architecture re"],
    ["enduser-type","customer","A","Architecture re"],
    ["enduser-type","consumer","A","Architecture re"],
    ["enduser-type","supplier","B","System Co"],
    ["enduser-type","customer","B","System Co"],
    ["enduser-type","consumer","B","System Co"]
  ]
  </code></pre>
  
  <p>... to this one ...</p>
  
  <pre><code>[
    ["enduser-type",["supplier", "customer", "consumer"],"A","Architecture re"],
    ["enduser-type",["supplier", "customer", "consumer"],"B","System Co"]
  ]
  </code></pre>
  
  <p>How can I perform this conversion?</p>
  
  <p>Thank you for your help</p>