Labels and titles in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this plot title code?

Consider the following R code that creates a simple plot with a title and axis labels. What will be the title of the plot when this code runs?

R Programming

plot(1:5, 1:5, main = "My Plot Title", xlab = "X Axis", ylab = "Y Axis")
title(main = "Overridden Title")

A Overridden Title

B X Axis

C Y Axis

D My Plot Title

💡 Hint

The title() function can override the main title set in plot().

The plot() function sets the initial main title to "My Plot Title". The subsequent title() call with main = "Overridden Title" replaces the main title on the plot.

❓ Predict Output

intermediate

What label appears on the x-axis?

What label will appear on the x-axis after running this R code?

R Programming

barplot(1:3, names.arg = c("A", "B", "C"), xlab = "Category")

A A, B, C

B Category

C 1, 2, 3

D No label

💡 Hint

xlab sets the label for the x-axis, names.arg sets the names for bars.

The xlab argument sets the label for the x-axis, so "Category" will appear as the x-axis label. The names.arg argument labels each bar but does not change the axis label.

🔧 Debug

advanced

Why does this plot title not appear?

This R code is intended to add a title to the plot, but no title appears. What is the cause?

R Programming

plot(1:10, 1:10)
title(main = "My Title", sub = "Subtitle")
title(xlab = "X Label")

A The xlab argument in title() does not set the x-axis label; it must be set in plot().

B The title() function cannot add subtitles; sub is ignored.

C The plot() function must include main argument to show any title.

D The title() function calls overwrite each other, so only the last call works.

💡 Hint

Check which arguments title() accepts and which must be set in plot().

The title() function accepts main, sub, and line arguments but does not accept xlab or ylab. Axis labels must be set in the plot() function or with separate axis labeling functions.

🧠 Conceptual

advanced

How to add multiple lines in a plot title?

Which option correctly adds a multi-line main title to a plot in R?

A plot(1:5, main = "Line 1\nLine 2")

B plot(1:5, main = c("Line 1", "Line 2"))

C plot(1:5); title(main = "Line 1\nLine 2")

D plot(1:5); title(main = c("Line 1", "Line 2"))

💡 Hint

Use newline characters in strings or multiple calls to title().

The newline character \n inside a string works in title() to create multi-line titles. The main argument in plot() does not interpret \n properly for multi-line titles, so using title() after plot() is the correct approach.

❓ Predict Output

expert

What is the output of this label and title code?

What will be the main title and axis labels of the plot after running this R code?

R Programming

plot(1:3, 1:3, main = "First Title", xlab = "X1", ylab = "Y1")
title(main = "Second Title", xlab = "X2")
title(ylab = "Y2")

A Main title: Second Title; X-axis label: X1; Y-axis label: Y1

B Main title: First Title; X-axis label: X1; Y-axis label: Y1

C Main title: First Title; X-axis label: X2; Y-axis label: Y2

D Main title: Second Title; X-axis label: X2; Y-axis label: Y2

💡 Hint

title() can override main and sub titles but not axis labels; check which labels are updated.

The first title() call overrides the main title. However, title() does not accept xlab or ylab arguments, so axis labels remain as set in plot(). The second title() call with ylab is ignored. So the final labels are main = "Second Title", xlab = "X1", ylab = "Y1".