JFreeChart XYAreaChart make areas start at smallest y-axis instead of 0

Question

I am trying to create an XYarea chart; but instead of the areas revolving around the 0 y-axis, I would like them to start from the bottom the smallest y-axis (-10 here). Here is the original graph from the JFreeChart example.

My desired results are something like this:

I have tried both XYarea and SstackedXYArea charts.