Package installation (install.packages) in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this R code?

Consider the following R code that attempts to install a package and then check if it is installed. What will be the output?

R Programming

if (!"ggplot2" %in% installed.packages()[,"Package"]) {
  install.packages("ggplot2")
  print("Installed ggplot2")
} else {
  print("ggplot2 already installed")
}

A Warning: package ‘ggplot2’ is not available

B ggplot2 already installed

C Error: object 'ggplot2' not found

D Installed ggplot2

💡 Hint

Think about what happens if the package is not installed yet.

The code checks if 'ggplot2' is in the list of installed packages. If not, it installs it and prints 'Installed ggplot2'. Otherwise, it prints 'ggplot2 already installed'.

❓ Predict Output

intermediate

What happens when you run install.packages with a wrong package name?

What will be the output of this R code snippet?

R Programming

install.packages("nonexistentpackage123")

A Warning: package ‘nonexistentpackage123’ is not available

B Installation succeeds silently

C Error: could not find function "install.packages"

D The package is installed but cannot be loaded

💡 Hint

Try to install a package that does not exist on CRAN.

R will warn that the package is not available because it cannot find it on CRAN or other repositories.

🔧 Debug

advanced

Why does this install.packages call fail?

This R code is intended to install the 'dplyr' package but fails with an error. What is the cause?

R Programming

install.packages(dplyr)

A Network connection error

B Syntax error: missing quotes around package name

C install.packages does not accept package names as strings

D dplyr package is already installed, so it fails

💡 Hint

Check how package names should be passed to install.packages.

The package name must be a string in quotes. Without quotes, R treats dplyr as an object, causing an error.

🧠 Conceptual

advanced

What does the 'repos' argument in install.packages do?

In R, what is the purpose of the 'repos' argument in the install.packages function?

A It specifies the repository URL from which to download the package

B It sets the local folder where the package will be installed

C It defines the version of the package to install

D It lists the dependencies to install along with the package

💡 Hint

Think about where R looks to find packages.

The 'repos' argument tells R which repository URL to use to find and download the package.

❓ Predict Output

expert

How many packages are installed after running this code?

Given the following R code, how many packages will be installed after it runs?

R Programming

pkgs <- c("ggplot2", "dplyr", "tidyr")
new_pkgs <- pkgs[!(pkgs %in% installed.packages()[,"Package"])]
if(length(new_pkgs)) install.packages(new_pkgs)
length(new_pkgs)

A 0

B 3

C Depends on which packages are already installed

D 1

💡 Hint

Check how new_pkgs is calculated based on installed packages.

The code checks which packages from the list are not installed yet and installs only those. The length of new_pkgs depends on the current system state.