First R program in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the simplest way to print text in R?

Use the print() function with the text inside quotes, like print("Hello, world!").

beginner

What does the following R code do?

print("Hello, world!")

It shows the text "Hello, world!" on the screen.

beginner

How do you write a comment in R?

Start the line with #. Anything after # is ignored by R.

beginner

What is the purpose of the print() function in R?

It shows information or results on the screen so you can see them.

beginner

Can you run R code directly in the console?

Yes! You can type R commands in the console and press Enter to see results immediately.

Which function prints text in R?

A echo()

B display()

C show()

D print()

The print() function is used to display text or values in R.

What will this code output?

print("Hi there!")

A Error

B Hi there!

C print("Hi there!")

D "Hi there!"

The print() function shows the text without quotes around it.

How do you write a comment in R?

A # comment

B // comment

C <!-- comment -->

D /* comment */

In R, comments start with #.

What happens if you run print(123) in R?

A It prints the number 123

B It prints "123" as text

C It causes an error

D It prints nothing

Numbers can be printed directly using print().

Where can you type R commands to run them immediately?

A In a text editor

B In a web browser

C In the R console

D In a spreadsheet

The R console lets you type and run commands instantly.

Explain how to write and run your first R program that prints a message.

Think about how you tell R to show words on the screen.

Describe how comments work in R and why they are useful.

Comments are notes for people, not for the computer.

Practice

1. What does the print() function do in R?

easy

A. It saves the text to a file.

B. It displays the text or value inside the parentheses on the screen.

C. It creates a new variable.

D. It deletes existing data.

Solution

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

   The print() function is used to show output on the screen in R.

2. Step 2: Compare options

   Only It displays the text or value inside the parentheses on the screen. correctly describes that print() displays text or values.

3. Final Answer:

   It displays the text or value inside the parentheses on the screen. -> Option B

4. Quick Check:

   print() shows output = It displays the text or value inside the parentheses on the screen. [OK]

Hint: Remember: print() shows output on screen [OK]

Common Mistakes:

• Thinking print() saves to a file
• Confusing print() with variable creation
• Assuming print() deletes data

2. Which of the following is the correct syntax to print the message "Hello, R!" in R?

easy

A. print("Hello, R!")

B. print(Hello, R!)

C. print('Hello, R!)

D. print["Hello, R!"]

Solution

1. Step 1: Check the use of quotes

   Text messages must be inside matching quotes. print("Hello, R!") uses double quotes correctly.

2. Step 2: Verify function syntax

   print() requires parentheses, not square brackets. print("Hello, R!") uses parentheses correctly.

3. Final Answer:

   print("Hello, R!") -> Option A

4. Quick Check:

   Quotes + parentheses correct = print("Hello, R!") [OK]

Hint: Use matching quotes inside print() parentheses [OK]

Common Mistakes:

• Missing quotes around text
• Mismatched or missing closing quotes
• Using square brackets instead of parentheses

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

print("Welcome to R programming")

medium

A. [1] "Welcome to R programming"

B. Welcome to R programming

C. Error: unexpected string

D. NULL

Solution

1. Step 1: Understand print() output format in R

   R prints output with an index [1] before the text when printing a character string.

2. Step 2: Match output with options

   [1] "Welcome to R programming" shows the correct R output format including the index.

3. Final Answer:

   [1] "Welcome to R programming" -> Option A

4. Quick Check:

   print() output includes [1] index = [1] "Welcome to R programming" [OK]

Hint: R shows [1] before printed strings [OK]

Common Mistakes:

• Ignoring the [1] index in output
• Expecting plain text without index
• Confusing output with error messages

4. Identify the error in this R code:

print('Hello R)

medium

A. Missing closing parenthesis

B. print() cannot print text

C. Mismatched quotes around text

D. Missing comma inside print

Solution

1. Step 1: Check quotes in the code

   The code starts with a single quote but does not close it properly, causing mismatched quotes.

2. Step 2: Verify parentheses

   The closing parenthesis is present, so the error is not missing parenthesis.

3. Final Answer:

   Mismatched quotes around text -> Option C

4. Quick Check:

   Quotes must match exactly = Mismatched quotes around text [OK]

Hint: Always close quotes properly inside print() [OK]

Common Mistakes:

• Ignoring missing quote errors
• Assuming parentheses are missing
• Thinking print() needs commas inside

5. You want to write a first R program that prints your name and age on separate lines. Which code will do this correctly?

hard

A. print("Name: Alice\nAge: 25")

B. print("Name: Alice")\nprint("Age: 25")

C. print("Name: Alice", "Age: 25")

D. print("Name: Alice")
print("Age: 25")

Solution

1. Step 1: Understand how to print multiple lines in R

   Using two separate print() calls prints on separate lines. The newline character \n inside a single print() prints \n literally, not a new line.

2. Step 2: Check code correctness

   print("Name: Alice") print("Age: 25") correctly uses two print() calls on separate lines with proper syntax.

3. Final Answer:

   print("Name: Alice") print("Age: 25") -> Option D

4. Quick Check:

   Separate print() calls for separate lines = print("Name: Alice") print("Age: 25") [OK]

Hint: Use separate print() calls for multiple lines [OK]

Common Mistakes:

• Using \n inside print() without escape
• Writing \n outside quotes causing syntax error
• Trying to print multiple lines in one print() without proper escape