title: Sankey plot with bands/links that can change width in R?
body: <p>Is it possible to make a sankey plot that looks like this in <code>R</code>?
  <a href="https://i.stack.imgur.com/jtvGP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jtvGP.png" alt="Example of required functionality"></a></p>
  
  <p>I've played around with the <code>networkD3</code> package, which works great if the sum of input = sum of output for each node, but I need a solution which supports bands/links that change in size between time periods. </p>
  
  <p>As far as I can work out, <code>networkD3</code> does not allow me to do this because you must specify the links with a single value (links have a fixed width/value).</p>
  
  <p>Is there anything out there, preferably for <code>R</code>, that can do this?</p>