Grammar of Graphics concept in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this ggplot2 code?

Consider the following R code using ggplot2. What will be the output when this code runs?

R Programming

library(ggplot2)
data <- data.frame(x = 1:3, y = c(3, 2, 1))
ggplot(data, aes(x = x, y = y)) + geom_point() + geom_line()

A A histogram of y values

B A bar chart showing counts of x values

C A scatter plot with points connected by lines in order of x values

D A boxplot of y grouped by x

💡 Hint

Think about what geom_point() and geom_line() do in ggplot2.

The code creates a scatter plot with points at (1,3), (2,2), and (3,1). The geom_line() connects these points in order of x, forming a line.

🧠 Conceptual

intermediate

Which component of Grammar of Graphics defines how data variables map to visual properties?

In the Grammar of Graphics, which component describes the mapping of data variables to visual aesthetics like color, size, or position?

A Aesthetics

B Statistics

C Geoms

D Facets

💡 Hint

Think about what controls the look of points or lines based on data.

Aesthetics define how data variables are mapped to visual properties such as color, size, shape, or position.

🔧 Debug

advanced

What error does this ggplot2 code produce?

Examine the code below. What error will it raise when run?

R Programming

library(ggplot2)
data <- data.frame(x = 1:5, y = c(2, 4, 6, 8, 10))
ggplot(data, aes(x = x, y = y)) + geom_point() + geom_line(aes(color = z))

A No error, plot displays with default color

B Error: geom_line() requires a numeric y aesthetic

C Error: geom_point() missing required aesthetics

D Error: object 'z' not found

💡 Hint

Check if all variables used in aes() exist in the data frame.

The variable 'z' is not defined in the data frame, so ggplot2 throws an error that object 'z' is not found.

📝 Syntax

advanced

Which option correctly adds a title to a ggplot?

Which of the following R code snippets correctly adds the title 'My Plot' to a ggplot object named p?

A p + ggtitle('My Plot')

B p + title('My Plot')

C p + labs(title = 'My Plot')

D p + set_title('My Plot')

💡 Hint

ggplot2 uses specific functions to add titles and labels.

The function ggtitle() adds a title to a ggplot. labs() can also add titles but requires the argument name 'title'.

🚀 Application

expert

How many layers does this ggplot have?

Given the code below, how many layers are added to the ggplot object?

R Programming

library(ggplot2)
data <- data.frame(x = 1:4, y = c(4, 3, 2, 1))
p <- ggplot(data, aes(x, y)) + geom_point() + geom_smooth(method = 'lm') + facet_wrap(~x)

A 3

B 2

C 4

D 1

💡 Hint

Count only the layers that add visual elements, not facets.

geom_point() and geom_smooth() each add one layer. facet_wrap() adds facets but does not add a layer. So total layers = 2.