The last sentence should read: Due to the 20 or so times the lines cross each other I wasn't sure how to modify the last example in ?polygon -- View this message in context: http://r.789695.n4.nabble.com/Polygon-Shading-Based-on-Relative-Line-Position-tp2132718p2132720.html Sent from the R help mailing list archive at Nabble.com.