Creating choropleth maps
Choropleth maps are pretty standard in diverse types of media. Usually, they display established geographical entities, such as countries and provinces, using polygons. Following this, we can indicate the value of a variable for a region using the color inside its polygon. Usually, we will use the color or hue to identify the values of a categorical variable. For qualitative and ordinal variables, we use color luminance and saturation instead.
We can read the polygons that are needed to create choropleth maps from a vector file in one Geographic Information System (GIS) file format. The Julia language ecosystem offers the pure Julia Shapefile and GeoJSON packages to read files in the homonymous GIS formats. To read other GIS formats, both vector and raster images, you can use the GDAL or ArchGDAL packages. These last packages are wrappers to the Geospatial Data Abstraction Library (GDAL), which can read and write multiple GIS formats.
The Shapefile and...
