ggplot() and aes() basics in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic ggplot object with the data frame 'df'.

R Programming

p <- ggplot([1])

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

Adf

Bgeom_point()

Caes

Dggplot

Attempts:

3 left

💡 Hint

Common Mistakes

Using aes or geom_point() directly inside ggplot() without specifying data.

Passing the function ggplot itself as argument.

The ggplot() function needs a data frame as its first argument to know which data to use.

2fill in blank

medium

Complete the code to map the variable 'x_var' to the x-axis inside aes().

R Programming

p <- ggplot(df, aes(x = [1]))

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

Ax_var

Bgeom_point

Cdf

Dy_var

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that is not in the data frame.

Passing the whole data frame instead of a variable name.

Inside aes(), you specify the variable names from the data frame to map to aesthetics like x or y axes.

3fill in blank

hard

Fix the error in the code by completing the aes() mapping for both x and y variables.

R Programming

p <- ggplot(df, aes(x = [1], y = [2])) + geom_point()

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

Ax_var

Bgeom_point

Cy_var

Ddf

Attempts:

3 left

💡 Hint

Common Mistakes

Using geom_point inside aes().

Using the data frame name instead of variable names.

Both x and y inside aes() must be variable names from the data frame to plot points correctly.

4fill in blank

hard

Fill both blanks to create a scatter plot mapping 'height' to x and 'weight' to y.

R Programming

p <- ggplot(data = df, aes(x = [1], y = [2])) + geom_point()

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

Aheight

Bweight

Cage

Dgender

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the variables for x and y.

Using variables not present in the data frame.

To plot height on the x-axis and weight on the y-axis, map these variable names inside aes().

5fill in blank

hard

Fill all three blanks to create a ggplot with data 'df', mapping 'age' to x, 'income' to y, and adding points.

R Programming

p <- ggplot([1], aes(x = [2], y = [3])) + geom_point()

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

Adf

Bage

Cincome

Dheight

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names outside of aes().

Mixing up the order of arguments.

The ggplot() function needs the data frame first, then inside aes() you map the variables for x and y axes.

Practice

1. What is the main purpose of the aes() function in ggplot()?

easy

A. To add titles and labels to the plot

B. To map data columns to visual properties like x and y axes

C. To create the plot background color

D. To save the plot as an image file

Solution

1. Step 1: Understand the role of aes()

   The aes() function defines how data columns are linked to visual elements like axes or colors.

2. Step 2: Compare options with aes() purpose

   Only To map data columns to visual properties like x and y axes correctly describes mapping data columns to x and y axes, which is the main use of aes().

3. Final Answer:

   To map data columns to visual properties like x and y axes -> Option B

4. Quick Check:

   Mapping data columns = A [OK]

Hint: Remember: aes() sets data to axes or colors [OK]

Common Mistakes:

• Thinking aes() adds titles or labels
• Confusing aes() with saving or styling functions
• Assuming aes() creates plot background

2. Which of the following is the correct syntax to start a scatter plot with ggplot() using data frame df and mapping x to column age and y to column height?

easy

A. ggplot(df, aes(x = age, y = height)) + geom_point()

B. ggplot(aes(x = age, y = height), df) + geom_point()

C. ggplot(df) + aes(x = age, y = height) + geom_point()

D. ggplot(df, geom_point(aes(x = age, y = height)))

Solution

1. Step 1: Recall correct ggplot() syntax

   The correct syntax is ggplot(data, aes(...)) + geom_* where data is first, then aes() inside ggplot.

2. Step 2: Check each option

   ggplot(df, aes(x = age, y = height)) + geom_point() matches the correct order and usage. The other options misuse argument order or place aes() outside ggplot().

3. Final Answer:

   ggplot(df, aes(x = age, y = height)) + geom_point() -> Option A

4. Quick Check:

   Data first, then aes() inside ggplot() = B [OK]

Hint: Put data first, then aes() inside ggplot() [OK]

Common Mistakes:

• Swapping data and aes() arguments
• Calling aes() outside ggplot()
• Putting geom_point() inside ggplot() arguments

3. What will be the output of this R code?

library(ggplot2)
df <- data.frame(x = 1:3, y = c(4, 5, 6))
ggplot(df, aes(x = x, y = y)) + geom_point()

medium

A. A scatter plot with points at (1,4), (2,5), and (3,6)

B. A bar chart showing counts of x values

C. An error because geom_point() is missing arguments

D. A line plot connecting points (1,4), (2,5), and (3,6)

Solution

1. Step 1: Understand the code components

   The code creates a data frame with x and y values, then plots points using geom_point() which draws scatter points.

2. Step 2: Identify the plot type and points

   geom_point() creates scatter points at coordinates from x and y columns: (1,4), (2,5), (3,6).

3. Final Answer:

   A scatter plot with points at (1,4), (2,5), and (3,6) -> Option A

4. Quick Check:

   geom_point() draws scatter points = D [OK]

Hint: geom_point() plots points at mapped x,y coordinates [OK]

Common Mistakes:

• Confusing geom_point() with geom_bar() or geom_line()
• Expecting a line plot instead of points
• Thinking geom_point() needs extra arguments

4. Identify the error in this code snippet:

ggplot(mtcars, aes(x = mpg, y = hp))
geom_point()

medium

A. aes() should be outside ggplot()

B. Incorrect column names mpg and hp

C. geom_point() cannot be used with mtcars dataset

D. Missing + operator between ggplot() and geom_point()

Solution

1. Step 1: Check how layers are added in ggplot2

   Layers like geom_point() must be added with a + operator after ggplot().

2. Step 2: Review the code for missing +

   The code calls ggplot() and then geom_point() on a new line without +, causing an error.

3. Final Answer:

   Missing + operator between ggplot() and geom_point() -> Option D

4. Quick Check:

   Use + to add layers in ggplot2 = C [OK]

Hint: Add + between ggplot() and geoms to avoid errors [OK]

Common Mistakes:

• Forgetting the + operator between layers
• Thinking aes() must be outside ggplot()
• Assuming dataset columns are incorrect without checking

5. You want to create a scatter plot using ggplot() with data frame df that has columns time, score, and group. You want points colored by group. Which code correctly achieves this?

hard

A. ggplot(df) + aes(x = time, y = score, color = group) + geom_point()

B. ggplot(df, aes(x = time, y = score)) + geom_point(color = group)

C. ggplot(df, aes(x = time, y = score, color = group)) + geom_point()

D. ggplot(df, geom_point(aes(x = time, y = score, color = group)))

Solution

1. Step 1: Understand how to map color by a data column

   Color mapping must be inside aes() so ggplot knows to use data values for color.

2. Step 2: Check each option for correct color mapping

   ggplot(df, aes(x = time, y = score, color = group)) + geom_point() correctly maps color inside aes() in ggplot().
   ggplot(df, aes(x = time, y = score)) + geom_point(color = group) sets color outside aes(), causing an error.
   ggplot(df) + aes(x = time, y = score, color = group) + geom_point() incorrectly treats aes() as a layer.
   ggplot(df, geom_point(aes(x = time, y = score, color = group))) incorrectly nests geom_point() inside ggplot().

3. Final Answer:

   ggplot(df, aes(x = time, y = score, color = group)) + geom_point() -> Option C

4. Quick Check:

   Map color inside aes() in ggplot() = A [OK]

Hint: Put color inside aes() to map by data column [OK]

Common Mistakes:

• Setting color outside aes() causing fixed color
• Adding aes() as a layer with +
• Putting geom_point() inside ggplot() arguments