title: Persistent rectangle selector
body: <p>I am trying to develop a pipeline to process astronomical data. At some point, I need to draw a rectangle over an image to select an area. I am doing that using matplotlib.widgets.RectangleSelector. It is very convenient for me to use it since it is very easy to use. The only "problem" that I have is that the rectangle that I draw on the axis disappears after I release the mouse button. Is there any way to make it persistent? I mean, is there any way that I can make it stay there even once I release the button?</p>
  
  <p>I am using Matplotlib's examples as reference.
  <a href="http://matplotlib.org/examples/widgets/rectangle_selector.html" rel="nofollow">http://matplotlib.org/examples/widgets/rectangle_selector.html</a></p>