You may also have a look here:

http://flowingdata.com/2010/11/23/how-to-make-bubble-charts/

Note the "Circles incorrectly sized by radius instead of area. Large values appear much bigger."

Similar point made here:
https://stat.ethz.ch/pipermail/r-help/2011-January/265475.html



Message: 44
Date: Mon, 22 Oct 2012 08:05:24 -0700 (PDT)
From: swertie <v_coudrain@voila.fr>
To: r-help@r-project.org
Subject: Re: [R] Represent point size according to frequency
Message-ID: <1350918324783-4647022.post@n4.nabble.com>
Content-Type: text/plain; charset=us-ascii

Thank you very much. I managed to do it with a similar approach and it looks
like what I expected.

--
Henrik Pärn
Centre for Conservation Biology
Department of Biology
Norwegian University of Science and Technology
NO-7491 Trondheim
NORWAY

Office: +47 735 96084
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