Package installation (install.packages) in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the install.packages() function in R?

The install.packages() function is used to download and install new packages from CRAN or other repositories so you can use additional functions in R.

beginner

How do you install the package named dplyr in R?

You run install.packages("dplyr") in the R console. This downloads and installs the dplyr package.

intermediate

Can you use install.packages() to update an already installed package?

Yes, running install.packages() again for a package will update it to the latest version if a newer one is available.

intermediate

What happens if you try to install a package that is already installed?

R will check the installed version and if it is the latest, it will not reinstall. Otherwise, it updates the package.

beginner

Why do you need to install a package only once but load it every time you start R?

Installing downloads and sets up the package on your computer. Loading with library() makes the package functions available in your current R session.

Which function do you use to install a package in R?

A require()

B install.packages()

C library()

D load.package()

The install.packages() function downloads and installs packages. library() and require() load installed packages.

What argument do you pass to install.packages() to install the package 'ggplot2'?

A "ggplot2"

B ggplot2

C install ggplot2

D package = ggplot2

You must pass the package name as a string, so use "ggplot2".

If you want to install a package from a specific CRAN mirror, which argument do you use?

A url

B mirror

C repos

D source

The repos argument lets you specify the CRAN mirror URL.

After installing a package, what function do you use to start using it in your R session?

A library()

B install.packages()

C load()

D use()

Use library() to load the package into your current R session.

What happens if you run install.packages() for a package that is already installed and up to date?

A It causes an error

B It uninstalls the package

C It installs an older version

D Nothing, it skips reinstalling

R checks the version and skips reinstalling if the package is already up to date.

Explain the difference between installing a package and loading a package in R.

Think about what happens once versus what happens every time you start R.

Describe how you would install a package from a specific CRAN mirror.

Look for the argument that controls the source location.

Practice

1. What is the main purpose of the install.packages() function in R?

easy

A. To download and install new packages on your computer

B. To load a package into the current R session

C. To update all installed packages automatically

D. To remove a package from your computer

Solution

1. Step 1: Understand the role of install.packages()

   This function downloads and installs packages from CRAN or other repositories to your computer.

2. Step 2: Differentiate from library()

   library() loads a package into the current R session but does not install it.

3. Final Answer:

   To download and install new packages on your computer -> Option A

4. Quick Check:

   install.packages() installs packages [OK]

Hint: Remember: install once, load many times [OK]

Common Mistakes:

• Confusing install.packages() with library()
• Thinking install.packages() loads packages immediately
• Assuming install.packages() updates packages

2. Which of the following is the correct syntax to install the package named "ggplot2" in R?

easy

A. install.packages("ggplot2")

B. install.packages<"ggplot2">

C. install.packages{'ggplot2'}

D. install.packages["ggplot2"]

Solution

1. Step 1: Recall correct function syntax

   The function install.packages() requires the package name as a string inside parentheses.

2. Step 2: Identify correct string notation

   In R, strings are enclosed in double or single quotes inside parentheses, so install.packages("ggplot2") is correct.

3. Final Answer:

   install.packages("ggplot2") -> Option A

4. Quick Check:

   Correct function call uses parentheses and quotes [OK]

Hint: Use parentheses and quotes for package names [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Using curly braces instead of parentheses
• Using angle brackets which are invalid

3. What will happen if you run the following code in R?

install.packages("dplyr")
library(dplyr)
print(class(dplyr))

medium

A. It installs dplyr, loads it, and prints "package"

B. It installs dplyr, loads it, and prints an error

C. It installs dplyr, loads it, and prints "character"

D. It installs dplyr, loads it, and prints "function"

Solution

1. Step 1: Understand the code sequence

   The code installs the package "dplyr", then loads it with library(), then checks the class of the object named dplyr.

2. Step 2: Analyze the object dplyr

   After loading, dplyr is not bound to any object in the environment; library() only attaches the namespace to the search path. So class(dplyr) produces an error: object 'dplyr' not found.

3. Final Answer:

   It installs dplyr, loads it, and prints an error -> Option B

4. Quick Check:

   class(dplyr) errors after library() [OK]

Hint: library() doesn't create a variable named after the package [OK]

Common Mistakes:

• Assuming dplyr is a package object after loading
• Expecting class to print "package"
• Confusing package loading with object creation

4. You tried to install a package using install.packages("tidyverse") but got an error saying "package 'tidyverse' is not available". What is the most likely cause?

medium

A. You need to restart R before installing

B. You forgot to load the package with library()

C. You misspelled the package name or it is not on CRAN

D. You must install packages using library() instead

Solution

1. Step 1: Understand the error message

   The error "package is not available" means R cannot find the package on the default repository.

2. Step 2: Identify common causes

   This usually happens if the package name is misspelled or the package is not on CRAN (the default repository).

3. Final Answer:

   You misspelled the package name or it is not on CRAN -> Option C

4. Quick Check:

   Package not found = misspelling or missing on CRAN [OK]

Hint: Check spelling and CRAN availability first [OK]

Common Mistakes:

• Confusing install.packages() with library()
• Restarting R unnecessarily
• Trying to install with library()

5. You want to install multiple packages at once: "ggplot2", "dplyr", and "tidyr". Which of the following commands correctly installs all three packages in one line?

hard

A. install.packages({"ggplot2", "dplyr", "tidyr"})

B. install.packages("ggplot2", "dplyr", "tidyr")

C. install.packages(["ggplot2", "dplyr", "tidyr"])

D. install.packages(c("ggplot2", "dplyr", "tidyr"))

Solution

1. Step 1: Recall how to pass multiple packages

   The install.packages() function accepts a vector of package names as a character vector.

2. Step 2: Identify correct vector syntax

   In R, a vector of strings is created with c(), so install.packages(c("ggplot2", "dplyr", "tidyr")) is correct.

3. Final Answer:

   install.packages(c("ggplot2", "dplyr", "tidyr")) -> Option D

4. Quick Check:

   Use c() to install multiple packages [OK]

Hint: Use c() to group package names in install.packages() [OK]

Common Mistakes:

• Passing multiple strings without c()
• Using square or curly brackets instead of c()
• Trying to install packages separately in one call