R Console and script files in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the R Console used for?

The R Console is where you type and run R commands one at a time. It shows results immediately, like a chat with the computer.

beginner

What is an R script file?

An R script file is a text file that holds many R commands saved together. You can run the whole file to do tasks step-by-step.

beginner

How do you run an R script file in RStudio?

You can run an R script by clicking the 'Run' button or pressing Ctrl+Enter to run the current line or selection.

beginner

Why use script files instead of typing commands only in the console?

Script files save your work so you can reuse or fix it later. The console forgets commands after you close it.

beginner

How can you save your R script file?

You save an R script file by clicking 'File' > 'Save' or pressing Ctrl+S, then choosing a name with '.R' extension.

What happens when you type a command in the R Console and press Enter?

A The console closes.

B The command runs immediately and shows the result.

C The command opens a new script file.

D The command is saved but not run.

Typing a command in the R Console and pressing Enter runs it right away and shows the output.

Which file extension is used for R script files?

A .R

B .rscript

C .txt

D .rs

R script files use the '.R' extension to identify them as R code files.

How can you run a single line of code from an R script in RStudio?

A Press Ctrl+Enter or click 'Run'.

B Press Ctrl+S.

C Close the script file.

D Type it again in the console.

Ctrl+Enter or the 'Run' button runs the current line or selected code from the script.

Why is it better to use script files instead of only the console?

A Script files cannot be edited.

B Console commands are faster.

C Console commands are saved automatically.

D Script files save your commands for later use.

Script files keep your commands saved so you can reuse or fix them anytime.

What does pressing Ctrl+S do in an R script window?

A Runs the script.

B Closes the script.

C Saves the script file.

D Clears the console.

Ctrl+S saves the current script file to your computer.

Explain the difference between using the R Console and an R script file.

Think about how you work with quick commands versus saving your work.

Describe the steps to create, run, and save an R script file in RStudio.

Imagine writing a recipe, testing it, and saving it for later.

Practice

1. What is the main purpose of the R Console?

easy

A. To type and run commands one at a time

B. To save many commands in a file

C. To create graphical plots only

D. To install R packages automatically

Solution

1. Step 1: Understand the R Console function

   The R Console allows users to type commands and see results immediately, one command at a time.

2. Step 2: Compare with script files

   Script files are used to save many commands to run later, not the console's main role.

3. Final Answer:

   To type and run commands one at a time -> Option A

4. Quick Check:

   R Console = run commands one by one [OK]

Hint: Console runs commands instantly, scripts save commands [OK]

Common Mistakes:

• Confusing console with script file
• Thinking console saves commands permanently
• Assuming console only creates plots

2. Which of the following is the correct way to run a script file named analysis.R in R?

easy

A. execute("analysis.R")

B. run("analysis.R")

C. source("analysis.R")

D. load("analysis.R")

Solution

1. Step 1: Recall R function to run scripts

   In R, the function source() is used to run commands saved in a script file.

2. Step 2: Check other options

   Functions like run(), execute(), and load() do not run script files; load() loads saved data, not scripts.

3. Final Answer:

   source("analysis.R") -> Option C

4. Quick Check:

   Run script = source() [OK]

Hint: Use source() to run saved R scripts [OK]

Common Mistakes:

• Using load() to run scripts
• Trying run() or execute() which don't exist
• Forgetting to use quotes around filename

3. What will be the output when you run the following commands in the R Console?

x <- 5
y <- 3
z <- x + y
print(z)

medium

A. NULL

B. 53

C. Error: object 'z' not found

D. 8

Solution

1. Step 1: Calculate the sum of x and y

   x is assigned 5, y is assigned 3, so z = 5 + 3 = 8.

2. Step 2: Print the value of z

   The print(z) command outputs the value stored in z, which is 8.

3. Final Answer:

   8 -> Option D

4. Quick Check:

   5 + 3 = 8 [OK]

Hint: Add variables then print result [OK]

Common Mistakes:

• Concatenating numbers as strings (53)
• Forgetting to assign z before print
• Expecting NULL output

4. You wrote this script file calc.R:

result <- a + b
print(result)

When you run source("calc.R") in the console, you get an error. What is the problem?

medium

A. Variables a and b are not defined before use

B. The print() function is misspelled

C. source() cannot run script files

D. The assignment operator <- is incorrect

Solution

1. Step 1: Check variable definitions

   The script uses variables a and b without assigning values first, causing an error.

2. Step 2: Verify other parts

   print() is correct, source() runs scripts, and <- is valid assignment in R.

3. Final Answer:

   Variables a and b are not defined before use -> Option A

4. Quick Check:

   Undefined variables cause errors [OK]

Hint: Define variables before using them in scripts [OK]

Common Mistakes:

• Assuming print() is wrong
• Thinking source() can't run scripts
• Confusing assignment operator syntax

5. You want to organize your R work by saving commands in a script file and running them all at once. Which approach is best?

hard

A. Use load() to run commands saved in a script

B. Write commands in a script file and use source() to run them

C. Save commands in a text file and open it in a text editor only

D. Type all commands directly in the console one by one

Solution

1. Step 1: Understand script file usage

   Script files save many commands so you can run them together later.

2. Step 2: Use source() to run scripts

   The source() function runs all commands in the script file at once.

3. Step 3: Evaluate other options

   Typing in console is manual and slow; text files alone don't run commands; load() loads data, not scripts.

4. Final Answer:

   Write commands in a script file and use source() to run them -> Option B

5. Quick Check:

   Scripts + source() = organized runs [OK]

Hint: Save commands in script, run with source() [OK]

Common Mistakes:

• Running scripts by typing manually
• Using load() instead of source()
• Not saving commands in R script format