On Tue, 28 Aug 2007, in microsoft.public.excel.charting,
Nevet said:
I'm looking to create a Venn diagram that depicts not only relationships
among entities but also their relative size. For example, Group A is of size
60, Group B, size 30, is a subset of A; Group C, size 20, is also a subset of
A, and includes an overlap of 15 with group B. In other words, B & C are
partially overlapping, and both fully included in A. I would like the
circles' areas and the overlapping portion to be proportionate to their
sizes.

Since you say B and C are entirely inside A, your problem boils down to
getting just two circles to overlap. I once used trigonometry in a BASIC
program, to work out where two such circles should be, although I don't
have the equation to hand anymore. You can get the proportionality of
the circles easily enough using a Bubble Chart type, but Excel bubble
charts don't preserve the relationship between bubble radius and XY
scale properly, so trigonometry wouldn't work there. If you wanted to
use Excel for the calculation and graph drawing, you'd have to draw
circular lines instead, using XY series.

To be honest, I doubt the value to your audience of
meticulously-calculated circles would be worth the effort, especially as
you have only one graph to draw. Have you considered just using a
drawing program and doing it freehand, estimating the proportions by
eye? Or maybe you could use the spreadsheet to create a rectangular
version, setting the cells to squares and coloring them in? This would
have the advantage that the readers could count the squares exactly.

--
Del Cotter
NB Personal replies to this post will send email to ,
which goes to a spam folder-- please send your email to del3 instead.