i have been using the fill function to highlight a region on my plot, but now i do not want it to be filled.  i have tried using alpha=0.1, but that also makes my edgecolor transparent.  is there a "box" function that does not fill a region yet still has the outline of the "box".  i tried using patch.rectangle, but it was not what i needed.

"The game of science can accurately be described as a never-ending insult to human intelligence." - Joćo Magueijo