Lab 4 [GIS6005]: Choropleth Mapping



For this map, I created a customized version of intervals after starting out with an Equal Intervals classification. I used 9 classes to capture one class for negligible changes (±0-0.01%) and four classes on either side of this. I selected two bin ranges for small population changes (±0-2.5% and ±2.5-5%), one bin size for medium population changes (±5-10%), and one bin size for large population changes (±10-20%). The selection of four classes on either side of negligible changes was done to more clearly represent the larger range of values for growth (versus shrinkage) in population trends.

I used a divergent color scheme from ColorBrewer for the legend. I used a neutral gray color for the negligible change category and then selected 4 shades of green for positive change and 4 shades of red for negative change. The colors are shaded similarly for similarly-sized histogram bins on both sides of the range, and the darkest colors in both ranges are used to indicate the highest values. Finally, in order to provide more context for the viewer on the scope of the ranges, I included a count value with each item to indicate the number of counties in each bin range.

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