Data Analysis

In-Class Exercise 7

Yu-You Liou

Shih Chien University

2026-08-03

Question 1

Load the patchwork package. Create three plots from mpg and save them as objects p1, p2, p3: a scatterplot of displ vs hwy, a boxplot of hwy by drv, and a bar chart of class. Compose them with patchwork operators:

• p1 | p2 (side by side)
• p1 / p2 (stacked)
• (p1 | p2) / p3 (two on top, one below)

Write one sentence explaining what | and / each do.

Question 2

Make two scatterplots from mpg that share the same colour mapping (colour = drv): displ vs hwy and displ vs cty. Place them side by side, first with a plain p1 | p2, then with

(p1 | p2) + plot_layout(guides = "collect")

Write one sentence describing what guides = "collect" changed and why the collected version is better when the two legends are identical.

Question 3

Take your composition from Question 2 and add an overall title and panel tags with plot_annotation():

(p1 | p2) +
  plot_layout(guides = "collect") +
  plot_annotation(title = "Fuel economy and engine size",
                  tag_levels = "a")

Write one sentence on why panel tags such as “(a)” and “(b)” are standard practice in academic figures.

Submission

Complete your answers in the official template from the Problem sets page (author = your student ID only; keep the UUID chunk). Knit to PDF, name it ex7-[StudentID].pdf, and upload it to the course pCloud folder before midnight of the following week.