<p>consider this a piecewise function(yes i know it doesn’t pass vert. line test)</p>
<p>[URL=<a href=“http://imageshack.us%5D%5BIMG%5Dhttp://img90.imageshack.us/img90/2084/circlethings1ap.png%5B/IMG%5D%5B/URL”>http://imageshack.us]
http://img90.imageshack.us/img90/2084/circlethings1ap.png
[/URL</a>]</p>
<p>I just mean the circles that indicate whether a point is included or excluded</p>