title: ggmap package plot filled polygon on map
body: <p>For days i'm searching on the web the most simple way to plot a shaded polygone above a map generated  with the get_map command. For the polygone I have a few (latitudes, longitudes) points.</p>
  
  <p>I know how to do this with *.shp files must it's too much time consuming for simple applications.</p>
  
  <p>If someone has a good tip to do this with in a simple way with R 3.0.2 ;-)</p>