Before you start

In this chapter we learn the spatial interactions of two spatial objects. We first look at the topological relations of two spatial objects (how they are spatially related with each other): specifically, st_intersects() and st_is_within_distance(). st_intersects() is particularly important as it is by far the most common topological relation economists will use and also because it is the default topological relation that sf uses for spatial subsetting and spatial joining.

We then follow with spatial subsetting: filtering spatial data by the geographic features of another spatial data. Finally, we will learn spatial joining. Spatial joining is the act of assigning attribute values from one spatial data to another spatial data based on how the two spatial datasets are spatially related (topological relation). This is the most important spatial operation for economists who want to use spatial variables in their econometric analysis. For those who have used the sp package, these operations are akin to sp::over().

Direction for replication

Datasets

All the datasets that you need to import are available here. In this chapter, the path to files is set relative to my own working directory (which is hidden). To run the codes without having to mess with paths to the files, follow these steps:

• set a folder (any folder) as the working directory using setwd()
  
• create a folder called “Data” inside the folder designated as the working directory (if you have created a “Data” folder previously, skip this step)
• download the pertinent datasets from here
• place all the files in the downloaded folder in the “Data” folder

Packages

Run the following code to install or load (if already installed) the pacman package, and then install or load (if already installed) the listed package inside the pacman::p_load() function.

if (!require("pacman")) install.packages("pacman")
pacman::p_load(
  sf, # vector data operations
  dplyr, # data wrangling
  data.table, # data wrangling
  ggplot2, # for map creation
  tmap # for map creation
)