How to align the x-axis of synchronized R dygraphs with single and double y-axis?

Say I have a dygraph with double y-axis, and another dygraph with a single y-axis. What I need here is that when user mouse over the first dygraph, the mouse is also displayed on the second dygraph on the same time-axis. Is that possible? Can we have some examples?

I see other posting some answer on this, but it is in JavaScript.