Communicating GIS Lab 9

This week for the lab we practiced creating multi-variable maps. In order to do this you have to start with two sets of normalized data that you can represent together in the same area of the map. For our example we have two sets of attribute data associated with the counties in the United States. If you are using a 9-class legend for the choropleth map you should have 3 classes for each of the variables. This will allow you to combine the data into the 9 total classes for the map. The creation of the attribute that you need in the final classification is pretty in-depth into the use of attribute tables in the ArcMAP program, but the basic step is to split each variable into three quantile classes, then add the attributes from each of the variables to crate the final attribute for the classification. In our lab we used 1,2,3 for the obesity variable and A,B,C for the Inactivity variable. So a typical result for a particular county would look like "A3" in the final attribute category.

 From here the counties are labeled using a unique values based on this "final attribute" and you have your bivariate choropleth map! The hardest part of making the map is the selection of your colors to represent your classes. You also have to build the 9-class grid from scratch on ArcMAP since there is no feature to do this. In the end the result is worth the effort and it makes for an aesthetically pleasing map.