PostgreSQL, PostGIS, pgRouting & QGIS
PostgreSQL is a powerful, open source object-relational database system. PostGIS and pgRouting are spatial database extensions for PostgreSQL that add support for geographic objects and geospatial routing. QGIS is a free and open source geographic information system.
These free and open source applications were used to query and process data in SQL, including spatial functions, and provide finished data for final visualization in R and RStudio.