Interactive maps

We present examples of how to construct interactive maps in Stata, using only built-in commands available even in secure environments. One can also use built-in commands to smooth geographic data as a pre-processing step. Smoothing can be done using methods from twoway contour, or predictions from a GMM model as described in Drukker , Prucha, and Raciborski (2013; SJ 13-2 pp.287-301). The basic approach to creating a map in Stata is twoway area, with the options nodropbase cmiss(no) yscale(off) xscale(off), with a polygon “shape file” dataset (often created by the user-written shp2dta by Kevin Crow, possible with a change of projection using programs by Robert Picard), and multiple calls to area with if qualifiers to build a choropleth or scatter to superimpose point data. This approach is automated by several user-written commands, and works well for static images, but is less effective for web content where a Javascript entity is desirable. However, it is straightforward to write out the requisite information using the file command, and to use open-source map tools to create interactive maps for the web. We present two useful examples.