In my blog post on improving the responsiveness of Shiny applications I mentioned a recent project I was involved with as part of a collaboration with Utah Tech University. Part of that project involved the construction of interactive Sankey (or to be extra-precise “alluvial”) diagrams using the d3 JavaScript library. One of the requirements was that the user could hover over a link or node in the diagram and see all the connections to or from that link or node highlighted.