title: How can I get the length of a single unit on an axis in matplotlib, in pixels?
body: <p>I want to make <a href="http://matplotlib.sourceforge.net/api/artist_api.html#matplotlib.lines.Line2D.set_markersize"><code>markersize</code></a> equal to a single unit in height.  It seems that <code>markersize</code> is in pixels.  How can I get at how large "1 unit" (along a given axis) is, in pixels?</p>