In ChartDirector, a bubble chart is just a scatter chart with variable
size symbols.
In this chart, two scatter layers with variable size glass sphere
symbols are shown.
This chart is the same as the previous chart, except semi-transparent
colors are used, so you can see through the bubbles. This is useful
if the bubbles can overlap extensively.
This chart uses solid spheres as bubbles.
A bubble chart using semi-transparent circular symbols.
In ChartDirector, bubbles are not limited to spheres or circles.
Other shapes can also be used.
Furthermore, the horizontal and vertical dimensions can be scaled
independently.
ChartDirector even supports using custom images as bubbles.