In this gist, I mentioned the addition of a yield curve that interacts with a hover event from the small multiple charts. Ideally, a reference line would track left to right to indicate date on the small multiples similar to this example. The appropriate yield curve for the data hovered would darken or change if selected.
Modified http://d3js.org/d3.v3.min.js to a secure url
https://d3js.org/d3.v3.min.js