24 · Spatial I: vector

Tuesday, Nov 17, 2026

Materials for this session are not published yet. They appear here before class.

Objectives

By the end of this session you can:

• Load and inspect vector data with sf.
• Verify a coordinate reference system and choose a projection deliberately.
• Run spatial joins with row-count discipline.
• Draw a choropleth, and validate a computed area against a published value.

What we cover

• What geography has measured: borders, catchments, access — and redlining’s long shadow.
• Geometries and attributes; the CRS, verified and never assumed.
• Spatial joins, with the same row-count discipline as session 5.
• Choropleths; the honest area lesson — st_area() against the Census’s published ALAND, and why they differ.

Verification habit. Overlay on a basemap you know; reconcile one area with the published value.