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
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. -- Bert Gunter Genentech Non-Clinical Statistics South San Francisco, CA "The business of the statistician is to catalyze the scientific learning process." - George E. P. Box> -----Original Message----- > From: r-help-bounces at stat.math.ethz.ch > [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of > Jennifer.Morin at colorado.edu > Sent: Thursday, June 02, 2005 11:57 AM > To: r-help at stat.math.ethz.ch > 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 > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html >
The symbol sizes, themselves, already encode the mean temperatures, so I'm not exactly sure what you want to put in a legend. Perhaps the circles and values for a few selected quantiles of the distribution to anchor the eye? If so, legend() with pch and pt.cex does not appear capable of doing what you want. However, it is simple to do by hand using symbols() and text()to place the circles and values in the plot. If you want them outside the plot region, set xpd to TRUE (in both symbols() and text()). -- Bert Gunter Genentech Non-Clinical Statistics South San Francisco, CA "The business of the statistician is to catalyze the scientific learning process." - George E. P. Box> -----Original Message----- > From: r-help-bounces at stat.math.ethz.ch > [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of > Jennifer.Morin at colorado.edu > Sent: Thursday, June 02, 2005 11:57 AM > To: r-help at stat.math.ethz.ch > 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 > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html >