Scatter plots (geom_point) in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a scatter plot using ggplot2.

R Programming

ggplot(data = mtcars, aes(x = wt, y = mpg)) + geom_[1]()

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

Apoints

Bpoint

Cgeom_point

Dgeom_points

Attempts:

3 left

💡 Hint

Common Mistakes

Writing the full function name 'geom_point' inside the blank causes syntax error.

Using 'points' or 'geom_points' which are not valid ggplot2 functions.

The correct function to add points in ggplot2 is geom_point(). You only write point inside geom_ to complete the function name.

2fill in blank

medium

Complete the code to map the color aesthetic to the 'cyl' variable.

R Programming

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

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

Acyl

Bmpg

Cwt

Dgear

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'mpg' or 'wt' which are mapped to x and y axes, not color.

Using 'gear' which is unrelated to this color mapping.

To color points by the number of cylinders, use the variable cyl inside the aes() function.

3fill in blank

hard

Fix the error in the code by completing the function name correctly.

R Programming

ggplot(mtcars, aes(x = wt, y = mpg)) + geom_[1]()

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

Ageom_point

Bpoints

Cgeom_points

Dpoint

Attempts:

3 left

💡 Hint

Common Mistakes

Including 'geom_' inside the blank causes syntax errors.

Using plural forms like 'points' or 'geom_points' which are invalid.

The correct function to add points is geom_point(). You only fill in 'point' after 'geom_'.

4fill in blank

hard

Fill both blanks to create a scatter plot with size mapped to 'hp' and shape mapped to 'cyl'.

R Programming

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

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

Ahp

Bmpg

Ccyl

Dwt

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up variables or using x/y variables for size or shape.

Using variables not present in mtcars.

To map size to horsepower, use hp. To map shape to cylinders, use cyl.

5fill in blank

hard

Fill all three blanks to create a scatter plot with color mapped to 'gear', size to 'hp', and shape to 'cyl'.

R Programming

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

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

Acyl

Bhp

Cgear

Dmpg

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same variable for multiple aesthetics.

Using variables not in the mtcars dataset.

Color is mapped to 'gear', size to 'hp', and shape to 'cyl' to create a detailed scatter plot.

Practice

1. What does the geom_point() function do in ggplot2?

easy

A. It adds a line connecting data points.

B. It creates a bar chart with grouped bars.

C. It creates a scatter plot showing points for data pairs.

D. It summarizes data with a boxplot.

Solution

1. Step 1: Understand the purpose of geom_point()

   The function geom_point() is used in ggplot2 to add points to a plot, which is the basis of a scatter plot.

2. Step 2: Identify the plot type created

   Scatter plots show the relationship between two numeric variables using dots, which matches what geom_point() does.

3. Final Answer:

   It creates a scatter plot showing points for data pairs. -> Option C

4. Quick Check:

   geom_point() = scatter plot points [OK]

Hint: Remember: geom_point() means dots on a scatter plot [OK]

Common Mistakes:

• Confusing geom_point() with geom_line()
• Thinking geom_point() creates bar charts
• Mixing up scatter plots with boxplots

2. Which of the following is the correct syntax to create a scatter plot with height on the x-axis and weight on the y-axis using ggplot2?

easy

A. ggplot(data) + geom_point(height, weight)

B. ggplot(data) + geom_point(aes(x = weight, y = height))

C. ggplot(data) + geom_point(x = height, y = weight)

D. ggplot(data) + geom_point(aes(x = height, y = weight))

Solution

1. Step 1: Check the correct use of aes() inside geom_point()

   The aesthetics mapping aes() must specify which variables go on x and y axes inside geom_point().

2. Step 2: Verify the order of variables

   The question asks for height on x-axis and weight on y-axis, so aes(x = height, y = weight) is correct.

3. Final Answer:

   ggplot(data) + geom_point(aes(x = height, y = weight)) -> Option D

4. Quick Check:

   Correct aes() syntax = ggplot(data) + geom_point(aes(x = height, y = weight)) [OK]

Hint: Always put aes(x=, y=) inside geom_point() [OK]

Common Mistakes:

• Swapping x and y variables
• Passing variables directly to geom_point() without aes()
• Omitting aes() entirely

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

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

medium

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

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

C. An error because aes() is missing.

D. A bar chart showing counts of x.

Solution

1. Step 1: Understand the data and mapping

   The data frame has x values 1, 2, 3 and y values 4, 5, 6. The aes() maps x to x-axis and y to y-axis.

2. Step 2: Identify the plot type from geom_point()

   geom_point() creates a scatter plot with points at the specified coordinates.

3. Final Answer:

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

4. Quick Check:

   geom_point() plots points at (x,y) pairs [OK]

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

Common Mistakes:

• Expecting a line plot instead of points
• Thinking aes() is missing causes error here
• Confusing bar chart with scatter plot

4. Identify the error in this code snippet:

ggplot(data) + geom_point(x = height, y = weight)

medium

A. Using ggplot() without data argument.

B. Missing aes() around x and y inside geom_point().

C. geom_point() cannot plot numeric data.

D. x and y should be swapped.

Solution

1. Step 1: Check how aesthetics are passed to geom_point()

   In ggplot2, x and y mappings must be inside aes() to link variables to axes.

2. Step 2: Identify the missing aes() call

   The code passes x and y directly to geom_point(), which is incorrect syntax.

3. Final Answer:

   Missing aes() around x and y inside geom_point(). -> Option B

4. Quick Check:

   Always use aes(x=, y=) inside geom_point() [OK]

Hint: Always wrap x and y in aes() inside geom_point() [OK]

Common Mistakes:

• Passing x and y directly without aes()
• Forgetting to provide data to ggplot()
• Swapping x and y unnecessarily

5. You want to create a scatter plot of mpg vs hp from the built-in mtcars dataset, but only for cars with cyl equal to 6. Which code correctly does this?

hard

A. ggplot(subset(mtcars, cyl == 6)) + geom_point(aes(x = hp, y = mpg))

B. ggplot(mtcars) + geom_point(aes(x = hp, y = mpg), subset = cyl == 6)

C. ggplot(mtcars) + geom_point(aes(x = hp, y = mpg)) + filter(cyl == 6)

D. ggplot(mtcars) + geom_point(aes(x = hp, y = mpg)) + subset(cyl == 6)

Solution

1. Step 1: Filter data before plotting

   To plot only cars with 6 cylinders, filter the data frame using subset(mtcars, cyl == 6).

2. Step 2: Use filtered data in ggplot()

   Pass the filtered data to ggplot(), then add geom_point() with correct aesthetics.

3. Final Answer:

   ggplot(subset(mtcars, cyl == 6)) + geom_point(aes(x = hp, y = mpg)) -> Option A

4. Quick Check:

   Filter data first, then plot with geom_point() [OK]

Hint: Filter data before ggplot() to plot subsets [OK]

Common Mistakes:

• Trying to filter inside geom_point() which is invalid
• Using filter() without dplyr or outside ggplot()
• Passing subset as argument to geom_point()