RE: [R] Adding a legend to a symbol plot

From: Berton Gunter <>
Date: Fri 03 Jun 2005 - 05:07:04 EST

Not an answer, but a note. Encoding the mean temperature as the circle radius is a bad idea: the eye perceives the area and so the radius^2, thus the perceived effect is the square of the actual temperature effect (Howard Wainer once referrred to this as "goosing up the effect by squaring the eyeball.") . You should encode the sqrt of the temperature as the radius so that the area is proportional to temperature. Details matter in graphical perception.

"The business of the statistician is to catalyze the scientific learning process." - George E. P. Box    

> -----Original Message-----
> From:
> [] On Behalf Of
> Sent: Thursday, June 02, 2005 11:57 AM
> To:
> Subject: [R] Adding a legend to a symbol plot
> I have created a symbol plot with circles that represent the
> mean temperature
> at lat/lon locations over the United States. The radius of the circle
> corresponds to the mean temperature. I would like to add a legend that
> identifies a range of temperatures (e.g. 0-10, 10-20, etc)
> with circles of the
> appropriate radii next to them. I've read the manual on how
> to add a legend,
> and I'm fine with adding one to the plot. However, I cannot
> get circles of
> different sizes to come up next to the ranges in my legend.
> All that is coming
> up are circles of all the same radius. In looking at the R
> manual, it appears
> that in order to get the right radius for the circles, I have
> to use the "pch"
> parameter in the "legend" command, but I'm unclear on how I
> should define this
> parameter. Can anyone help?
> thanks,
> Jennifer Morin
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> mailing list PLEASE do read the posting guide! Received on Fri Jun 03 05:17:39 2005

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