title: Pyplot: vertical gradient fill under curve?
body: <p>I'm wondering if there's a way to fill under a pyplot curve with a vertical gradient, like in this quick mockup:</p>
  
  <p><img src="https://i.imgur.com/ZoWCwRb.png" alt="image"></p>
  
  <p>I found this hack on StackOverflow, and I don't mind the polygons if I could figure out how to make the color map vertical: <a href="https://stackoverflow.com/questions/18215276/how-to-fill-rainbow-color-under-a-curve-in-python-matplotlib">How to fill rainbow color under a curve in Python matplotlib</a></p>