From boundaries to choropleths.
Continue Lecture 6 from slide 28, “Choropleth Maps,” then begin Classwork 5. Join smoke data to county boundaries, choose readable color scales, and explain the comparisons each map supports.
Monday, October 12 is Fall Break—no class.
This week
Join and check
- Keep GEOID as text so county codes retain their leading zeros.
- Check keys and row counts before joining smoke estimates to geometry.
- Keep missing values distinct from zero.
Color and comparison
- Compare categorical, continuous, and binned color scales.
- Use a meaningful midpoint when choosing a diverging scale.
- Distinguish concentrations, counts, rates, and population-weighted summaries.
Explain the map
- Use common scales when comparing days in small multiples.
- State the date, units, geography, and source in each figure.
- Identify the measurement and design limits of each comparison.
Lecture slides
Classwork
Classwork 5: Map Canadian Wildfire Smoke with geom_sf()
Begin the core path—Parts 0–4 and Part 7A—to read and check the data, layer boundaries, choose a projection, join smoke estimates, compare counts and rates, and draw daily small multiples. The remaining parts provide further practice with monitors, fires, plumes, spatial joins, and population-weighted summaries.
Research and data guides
When Canadian smoke crosses the border
Use the research guide to connect a map to the question it measures and the data guide to document sources, variables, units, and missing values. The Research Kick-off Report is due Tuesday, October 20.
By the end of Week 8
Prepare the following:
- a checked join between county boundaries and smoke data, with the row count and key documented;
- continuous and binned maps of the same smoke measure, with a brief explanation of the scale choices;
- daily small multiples with a common color scale; and
- captions stating each figure’s date, units, geography, source, and one limitation.