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RE: st: how to graph pie 3d-solid?


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: how to graph pie 3d-solid?
Date   Sat, 16 Oct 2010 18:59:01 +0100 (BST)

--- On Sat, 16/10/10, Grace Jessie wrote:
> thank you for your explanation, though I do not quiet
> understand,especially "...distort the angles...".
> The graph is very common,isn't it?

Yes, it is common (in certain areas) and it is also very wrong.

Look at a pie chart: how does it convey information? Large proportions
get slices with large angles at the point at the center of the pie, and
small proportions get slices with small angels at the point at the center
of the pie. Now think about what happens when we create a the 
illusion of 3D. We do that by distorting angles. Think of how we display 
a cube, we know all the angels are 90 degrees, but when we draw a cube, 
they certainly are not 90 degrees when create the illusion of 3D. This is
distortion of angels is necesary when we want to create the illustion of
3D, and that is why a 3D pie chart is such a bad graph, it distorts the
very information we are trying to convey.

> By the way, whether Stata can only draw plane graphs?

There some possibilties of doing things in 3D in Stata, but not many.

Hope this helps,
Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
--------------------------


      

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