title: Can I link actions between two d3 charts?
body: <p>Very casual javscript user here. Hopefully this makes sense.</p>
  
  <p>I am tracking 20 different series on a stacked area chart with nvd3.js. These series fluctuate between positive and negative values, some on a huge base and some on a small base. The result is that - when one of the really big series is below the x axis - it pushes everything else underneath too, and the positive series won't appear above the x axis until you filter out the bigger players using the key.</p>
  
  <p>The technically inelegant but good looking solution I have come up with is to split all of my negative values into one array, and all of my positives into another. The top half of the page is a positive values graph, the bottom half is negative values and they line up pretty nicely.</p>
  
  <p>The weakness with this approach is when you go to interact with it as an end user. If I filter out a series (by unchecking it in the key) or change the graph mode (with the type selector) or zoom in on a series (by clicking it so the graph refocuses to that series only) then it will only affect whichever graph you clicked on. I would like to adjust these three click events (and any others I've missed?) so that your action is synchronised across both graphs.</p>
  
  <p>Is this achievable? Any reading material I can dig through where somebody has done something similar? I imagine linking two representations of one data set (e.g a pie and column graph) is vaguely analogous.</p>