Chapter 9 — Practice Demo Lab: Reference Solution

Lab: Build a chart that tells a story

Note

Reference solution for the Chapter 9 Practice Demo Lab (Tasks 1–7 of Lab: Build a chart that tells a story). The graded Canvas lab has its own private answer key.

Task 1 — Pick a question

Worked example: “Did BC harvest area decline after 2010?” (any of the three suggested questions works).

Task 2 — Choose the right geom

The question is about change over time, so a line chart (geom_line) makes the trend visible. (A bar chart also works; scatter, histogram, and boxplot do not answer a “trend over time” question well.)

Tasks 3–4 — Build and polish the plot

bc <- read_excel(here("data","bc_disturbance_reforestation.xlsx"), sheet="Data")

p <- ggplot(bc, aes(Fiscal_Year, Harvested_ha)) +
  geom_line(linewidth = 1, colour = "#2D6A4F") +
  geom_vline(xintercept = 2010, linetype = "dashed", colour = "grey50") +
  scale_y_continuous(labels = label_comma()) +
  labs(title = "BC harvested area declined and flattened after 2010",
       x = "Fiscal year", y = "Harvested area (ha)",
       caption = "Source: Environmental Reporting BC, Trends in Silviculture in B.C.") +
  theme_minimal(base_size = 12)
p

Line chart of BC harvested area in hectares by fiscal year from 1987 to 2023, with a dashed vertical line at 2010; harvest is broadly lower and flatter after 2010 than in the 1990s. — BC area harvested (ha) by fiscal year, 1987–2023, with 2010 marked.

Task 5 — Save (with the plot checklist)

Checklist: geom fits the question (line, ✔); x/y are fiscal year vs harvested area (✔); axis labels include the unit ha (✔); title, subtitle, and a source caption are present (✔); and it saves into outputs/:

ggsave(here("outputs", "bc_harvest_trend.png"), p, width = 7, height = 4, dpi = 300)

Task 6 — Caption it

This chart shows BC harvested area by fiscal year. The main pattern is a decline and flattening after about 2010 relative to the 1990s peak, measured in hectares.

Task 7 — Submit

Submit the saved PNG, the plot code (Tasks 3–4), and the caption — with all group members’ names. (Graded lab: follow Canvas.)