This example show three series, there's nothing special about them. The thing that is special, that they all have what I call mouse tracking. Flotr observes the 'flotr:mouseover' event, and shows a point on the overlay canvas whenever the mouse comes near a datapoint.
You can pass the mouse tracking options as the third argument of Flotr.draw(), or you can pass
the options per series. Hereby, you can enable or disable mousetracking for certain series. As you can see,
I disabled mouse tracking for the blue line (which is series d1).
Finished? Go to the example index page or the Flotr Documentation Pages.