Bill -

Unfortunately, you cannot change the transparency of the bubbles in the
bubble chart. However, you can still get this effect by using custom
markers for the bubble chart. Draw come circles in the worksheet (any
size, they will scale to the size of the bubbles). Color them
appropriately and assign a transparency value; old Excel versions allow
only Yes (50%??) or No to transparency, while Excel 2003 offers any
value between 0 and 100%. Copy a circle, select the chart series, then
the point, then use Ctrl-V to paste the circle as the custom marker for
that bubble. Repeat for the other colors.

In a bubble chart, Excel has a default maximum size for a bubble, which
it uses for the largest bubble value in the chart. The default is about
25% of the smaller of the height or width of the plot area of the chart.
So there is no direct correlation with the axis scales. If you change
the default percentage (Excel accepts 0 to 300%), you merely tell Excel
how large to make the largest bubble.

More about bubble charts and custom chart markers:

http://peltiertech.com/Excel/ChartsH...wToBubble.html
http://peltiertech.com/Excel/Charts/...bbleSizes.html
http://peltiertech.com/Excel/ChartsH...omMarkers.html

- Jon
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Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
Tutorials and Custom Solutions
http://PeltierTech.com/
_______


Bill Hall wrote:

I am using three points to create a Venn Diagram with the Excel Bubble Chart.

At the moment, the bubbles have no FILL; if I use a different colour FILL in
each circle, how can I use the TRANSPARANCY so that I might be able to see
the common, and triple overlapping area?

Is there any relationship between the scale of the grid numbers (x,y), and
the radius number (r)? (There doesn't appear to be!)

What does the "scale the bubble size nnn% to the default" mean?

Thanks in anticipation

Bill Hall