12 · Communicating with graphics

Thursday, Oct 1, 2026

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

Objectives

By the end of this session you can:

  • Build a ggplot from data-to-aesthetic mappings.
  • Test a pooled pattern by disaggregating and replotting.
  • Facet, theme, label, and export a figure to an exact spec.
  • Critique a figure cold.

What we cover

  • ggplot2 from grammar to publication grade: aesthetics, geoms, scales.
  • cor() and lm() at one-line depth: a correlation you can quote, a fitted line on a scatter — sessions 19 and 20 lean on both.
  • Disaggregate-and-replot — does the pooled pattern survive?
  • Facets, themes, labels, exact-size export — and when to export pixels (PNG) versus resolution-free vectors (PDF), which journals ask about.
  • One geom is a map: the course’s air-quality monitors on a California outline — the first map of the semester, ten weeks before the spatial sessions.
  • Instruments are the plots you make for yourself; this is the other half — figures made for readers.

Verification habit. Does the figure survive without you in the room to explain it?