Hello Scott,

Thank you for the tips (I have posted the issue on the google group too), but there's nothing on these or other websites that gives an answer on our question.
Following the traditional used rules of making a symbol plot, the used symbols should have the same proportions, based on area, then the values have.
Unfortunately, this is not so in the plots we make with the code below (scale_area).


Yours sincerely,

Ann Frederix

----- Original Message ----- 
  From: Scott Chamberlain 
  To: Strategische Analyse CSD Hasselt 
  Sent: Monday, March 14, 2011 4:05 PM
  Subject: Re: [R] proportional symbol map ggplot


  There is a ggplot2 google groups mailing list that you may get more appropriate help from:


  http://groups.google.com/group/ggplot2?pli=1


  and the ggplot2 website is very helpful
  http://had.co.nz/ggplot2/
  On Monday, March 14, 2011 at 9:41 AM, Strategische Analyse CSD Hasselt wrote:

    Hello,

    we want to plot a proportional symbol map with ggplot. Symbols' area should 
    have the same proportions as the scaled variable.
    Hereby an example we found on 
    http://www.r-bloggers.com/bubble-chart-by-using-ggplot2/ . In this example 
    we see the proportions of the symbols' area are different from the 
    proportions of the scaled variable:

    crime <- 
    read.csv("http://datasets.flowingdata.com/crimeRatesByState2008.csv", 
    header=TRUE, sep="\t")
    p <- ggplot(crime, aes(murder,burglary,size=population, label=state))
    p <- p+geom_point(colour="red") +scale_area(to=c(1,20))+geom_text(size=3)

    Example:
    proportion population Pennsylvania/Tennessee= 2.003
    proportion symbols' area Pennsylvania/Tennessee= +/- 2.50

    proportion population California/Florida= 2.005
    proportion symbols' area California/Florida= +/-2.25

    What we would like is that the proportion of the symbols' area is also equal 
    to 2.0.

    We see the same in the legend:
    proportion population 1.6e+07 / 4.0e+06 = 4.0
    proportion symbols' area 1.6e+07 / 4.0e+06= +/-5.0


    Thanks in advance!

    Ann Frederix
    Robbie Heremans

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