"Synchronize" two graphs data

Hey there

I was wondering if there's a way to "synchronize" data from two different graphs to achieve the following:
The idea is that each circle corresponds to the vertically aligned month.

If I can't do this, I was thinking about drawing the bottom line with the circles independently of the graph data. But for that I would need to know the space the y axis labels take on the left (if that's acceptable, I can PR adding that value to the API). This way, I can compute the width of each tick easily.