>When plotting an X-Y scatterplot, how can I detect if several points have
>plotted on top of each other?
>
>Is there an existing routine detect and count how many points plot in the 
>same space?

If you're referring to "physical screen X,Y locations", then I'd use 
GETCPIXEL before drawing a point to see if the location was 'background 
color' or not.

If you're referring to the "logical" X,Y location, independent of any 
scaling you're doing to display it on the screen, then you'll have to 
keep track yourself; refer to the recent Zombies discussion for ideas...

Bill