Faceting for subplots in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a scatter plot with facets by the variable 'cyl'.

R Programming

library(ggplot2)
ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point() + facet_[1](~ cyl)

Drag options to blanks, or click blank then click option'

Afacet

Bgrid

Cwrap

Dplot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'facet_grid' instead of 'facet_wrap' when only one variable is used.

Misspelling the function name.

The facet_wrap function creates subplots (facets) wrapped by the variable specified.

2fill in blank

medium

Complete the code to facet the plot by 'cyl' and 'gear' using a grid layout.

R Programming

ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point() + facet_grid([1] ~ [2])

Drag options to blanks, or click blank then click option'

Acyl

Bgear

Cmpg

Dwt

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of variables.

Using variables not in the dataset.

facet_grid takes two variables separated by ~ to create a grid of subplots by rows and columns.

3fill in blank

hard

Fix the error in the code to facet by 'cyl' using facet_wrap.

R Programming

ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point() + facet_wrap(~ [1])

Drag options to blanks, or click blank then click option'

Agear

Bcyl

Ccyls

Dwt

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that does not exist in the dataset.

Adding extra characters to the variable name.

The variable name must exactly match the dataset column. 'cyl' is correct; 'cyls' is not a column.

4fill in blank

hard

Fill both blanks to facet the plot by 'cyl' in rows and 'am' in columns.

R Programming

ggplot(mtcars, aes(x = hp, y = mpg)) + geom_point() + facet_grid([1] ~ [2])

Drag options to blanks, or click blank then click option'

Acyl

Bam

Cgear

Dwt

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the variables in the wrong order.

Using variables not present in the dataset.

facet_grid uses the first variable for rows and the second for columns. Here, 'cyl' is rows and 'am' is columns.

5fill in blank

hard

Fill all three blanks to create a faceted plot with 'cyl' wrapped, color by 'gear', and size by 'hp'.

R Programming

ggplot(mtcars, aes(x = wt, y = mpg, color = [1], size = [2])) + geom_point() + facet_wrap(~ [3])

Drag options to blanks, or click blank then click option'

Agear

Bhp

Ccyl

Dam

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the variables for color and size.

Using the wrong variable for faceting.

The color aesthetic is set to 'gear', size to 'hp', and faceting is done by 'cyl' using facet_wrap.

Practice

1. What is the main purpose of faceting in R plotting with ggplot2?

easy

A. To save the plot as an image file

B. To change the color of points in a plot

C. To add titles to the plot

D. To split one plot into multiple smaller plots based on categories

Solution

1. Step 1: Understand faceting concept

   Faceting divides a single plot into multiple smaller plots based on categories in the data.

2. Step 2: Identify purpose in ggplot2

   In ggplot2, faceting helps compare groups by creating subplots for each category.

3. Final Answer:

   To split one plot into multiple smaller plots based on categories -> Option D

4. Quick Check:

   Faceting = split plot by category [OK]

Hint: Faceting means splitting plots by groups [OK]

Common Mistakes:

• Confusing faceting with coloring points
• Thinking faceting adds titles
• Believing faceting saves files

2. Which of the following is the correct syntax to create subplots by one variable using facet_wrap in ggplot2?

easy

A. ggplot(data) + geom_point() + facet_wrap(~ variable)

B. ggplot(data) + geom_point() + facet_grid(variable)

C. ggplot(data) + geom_point() + facet_wrap(variable)

D. ggplot(data) + geom_point() + facet_grid(~ variable)

Solution

1. Step 1: Recall syntax for facet_wrap

   facet_wrap requires a formula with tilde (~) and the variable name, like ~ variable.

2. Step 2: Check options

   ggplot(data) + geom_point() + facet_wrap(~ variable) uses facet_wrap(~ variable), which is correct syntax for faceting by one variable.

3. Final Answer:

   ggplot(data) + geom_point() + facet_wrap(~ variable) -> Option A

4. Quick Check:

   facet_wrap syntax = ~ variable [OK]

Hint: Use ~ before variable in facet_wrap() [OK]

Common Mistakes:

• Omitting the tilde (~) before variable
• Using facet_grid without formula
• Confusing facet_wrap and facet_grid syntax

3. What will be the result of this code?

library(ggplot2)
data <- data.frame(x=1:6, y=6:1, group=c('A','A','B','B','C','C'))
ggplot(data, aes(x, y)) + geom_point() + facet_wrap(~ group)

medium

A. A single plot with all points colored by group

B. Three separate plots, one for each group A, B, and C

C. An error because facet_wrap needs two variables

D. A plot with points connected by lines

Solution

1. Step 1: Understand data and faceting

   Data has groups A, B, and C. facet_wrap(~ group) creates one subplot per group.

2. Step 2: Predict output

   The code will produce three separate plots, each showing points for groups A, B, and C respectively.

3. Final Answer:

   Three separate plots, one for each group A, B, and C -> Option B

4. Quick Check:

   facet_wrap splits plot by group [OK]

Hint: facet_wrap(~ group) makes one plot per group [OK]

Common Mistakes:

• Expecting one combined plot with colors
• Thinking facet_wrap requires two variables
• Assuming points connect with lines

4. Identify the error in this code snippet:

ggplot(data, aes(x, y)) + geom_point() + facet_grid(group)

medium

A. facet_grid requires a formula with ~, like facet_grid(~ group)

B. geom_point() should come after facet_grid()

C. aes() must include color=group for faceting

D. facet_grid cannot be used with geom_point()

Solution

1. Step 1: Check facet_grid syntax

   facet_grid requires a formula input with tilde (~), e.g., facet_grid(~ group).

2. Step 2: Identify error in code

   The code uses facet_grid(group) without ~, causing a syntax error.

3. Final Answer:

   facet_grid requires a formula with ~, like facet_grid(~ group) -> Option A

4. Quick Check:

   facet_grid needs ~ before variable [OK]

Hint: Always use ~ in facet_grid() formula [OK]

Common Mistakes:

• Omitting ~ in facet_grid()
• Changing order of geom_point and facet_grid
• Adding unnecessary color aesthetic for faceting

5. You want to create a grid of plots faceted by two variables: gender (rows) and age_group (columns). Which code correctly does this in ggplot2?

hard

A. ggplot(data) + geom_point() + facet_wrap(~ gender + age_group)

B. ggplot(data) + geom_point() + facet_grid(~ gender + age_group)

C. ggplot(data) + geom_point() + facet_grid(gender ~ age_group)

D. ggplot(data) + geom_point() + facet_wrap(gender ~ age_group)

Solution

1. Step 1: Understand faceting by two variables

   facet_grid(rows ~ columns) creates a grid with rows and columns faceted by variables.

2. Step 2: Match variables to rows and columns

   gender should be rows, age_group columns, so syntax is facet_grid(gender ~ age_group).

3. Final Answer:

   ggplot(data) + geom_point() + facet_grid(gender ~ age_group) -> Option C

4. Quick Check:

   facet_grid(rows ~ columns) = gender ~ age_group [OK]

Hint: Use facet_grid(row ~ column) for two variables [OK]

Common Mistakes:

• Using facet_wrap for two variables as grid
• Swapping rows and columns in formula
• Omitting ~ or using wrong formula syntax