Dear Naomi,
At 07:47 AM 1/9/2004 -0500, Naomi B. Robbins wrote:
Apologies. I should have been more specific. There is a chapter on roses in
Wainer's "Visual Revelations." Florence Nightingale introduced these plots
in 1858. Other names for them are coxcomb plots, radial area plots,
Nightingale's pies, and wedges plots. Harris in "Information Graphics" calls
them sector graphs. While a pie chart has fixed radius and varies the angles,
these plots have fixed angles and vary the radius: the radius varies with the
square root of the data. Nightingale's example can be seen at the following
sites:
http://www.florence-nightingale.co.uk/small.htm
http://www.math.yorku.ca/SCS/Gallery/historical.html
It's clear from the latter that they can be drawn with SAS, but I don't have
or know how to use SAS.
Michael Friendly's four-fold plots (which are coxcomb-like plots for 2 x 2
contingency tables -- Wainer discusses a similar display) are implemented
in R, both in the base package and in the vcd (visualizing categorical
data) package. You might be able to adapt this code to your needs.
While we're on the subject, I'd also be interested in your comments on them.
Clearly they are of historical interest. They lack some of the weaknesses of
pies, such as comparing angles.
Actually, the areas of pie segments, as well as the angles and arc lengths,
are proportional to the quantity plotted, so this isn't an argument for
coxcombs.
Since the same category is always in the same
position, it is easier to compare multiple roses than pies.
This is a better point, I think.
I hope that this helps,
John
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John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox@mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
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