Since double-variable choropleths are very hard to understand, my goal was to create a very straightforward one. This was a big conceptual/design challenge. The main thing I did was drop any mention of numbers in the legend and instead used "low/high", based on standard deviations away from the mean.
Basically I created a hypothesis to "test", which is that the lowest-density county will have the lowest crime rate and the highest-density will have the highest crime rate ("urbanization causes a rise in crime rates"). After doing the math, I plotted the points in excel and saw that a fair number of counties were way outside this basic regression line. This very simple "model" doesn't predict urbanized counties well (I added dots to show the major cities, Charlotte, Raleigh-Durham, etc.) to show this to the viewer.
[One problem is that the dark-green counties don't have "low" crime rates- They have crimes rates much lower than *predicted* If density is 6 standard deviations above average, and crime is "only" 3 above average [which is still high in absolute numbers], the county is dark green). I'm not sure how to show this in a very simple manner.]
I probably made this needlessly hard, and wound up doing a lot of math/statistics to derive this map. I'm still not sure how logical it all is to the viewer.
1 comment:
Great Little BLog, Shame your course finished. If you still check back, have you ever thought about turning some of your maps into raised relief ones? such as these? http://www.aboveandbeyond.co.uk/Maps,+Guides,+Globes,+Gifts/3D+Relief+Maps/list/f1-f2 just a thought, could produce some interesting results.
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