Proportional Venn Diagrams

[Guest]

Greetings Excel gurus,

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.

Does anybody know how this can be done? (It doesn't have to be in Excel if
someone can recommend a better tool or application for this process, ideally
in Office 2007 or a freely downloadable piece of software.)

Thanks for any suggestions or pointers.

--Nevet

 

[Del Cotter]

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.

 

[Guest]

Del, Thanks for the reply. I believe you are correct & will simply use
freehand drawing for my purpose. I was hoping that Excel or some other
charting program had this functionality, but if not, I can still make (or
even exaggerate my point visually.

--Nevet

 

[Arthur Tabachneck]

Nevet,

Since the same question has been asked on the SAS b-board recently, I
presume that a number of people are starting to show interest in the
presentation method.

I don't have an excel solution, but did find a paper that describes
how to do it, as well as a Java applet that accomplishes the task.

Possibly someone on this board can translate the logic into Excel?

The paper and applet can be found at:

http://www.cs.uvic.ca/~ruskey/Publications/VennArea/VennArea.pdf
http://www.cs.uvic.ca/~schow/DrawVenn/instructions.html

HTH,
Art

 

[Guest]

Very cool! Thanks for the pointer!