Code chunks and output in R Programming - Mini Project: Build & Apply

Code chunks and output

📖 Scenario: You are learning how to write and run code chunks in R. This is useful when you want to organize your code and see the results step by step.

🎯 Goal: You will create a simple R script with code chunks that assign values, perform calculations, and print the results.

📋 What You'll Learn

Create a variable with a specific value

Create a helper variable for calculation

Use a code chunk to perform a calculation

Print the final result

💡 Why This Matters

🌍 Real World

Organizing code into chunks helps you write clear and easy-to-follow scripts for data analysis or reports.

💼 Career

Many data jobs require writing clean R code that shows intermediate results clearly for collaboration and debugging.

1

Create a variable called number and assign it the value 10

Write a line of R code to create a variable called number and set it equal to 10.

R Programming

# Create a variable called number and assign 10
# Your code here

Hint

Use the assignment operator <- to assign the value.

2

Create a variable called multiplier and assign it the value 5

Write a line of R code to create a variable called multiplier and set it equal to 5.

R Programming

number <- 10
# Create a variable called multiplier and assign 5
# Your code here

Hint

Use the assignment operator <- again to assign the value.

3

Create a variable called result that multiplies number by multiplier

Write a line of R code to create a variable called result and set it equal to number multiplied by multiplier.

R Programming

number <- 10
multiplier <- 5
# Create a variable called result that multiplies number by multiplier
# Your code here

Hint

Use the * operator to multiply the two variables.

4

Print the value of result

Write a line of R code to print the value of the variable result.

R Programming

number <- 10
multiplier <- 5
result <- number * multiplier
# Print the value of result
# Your code here

Hint

Use the print() function to display the value.

Practice

1. What is the purpose of an R code chunk in an R Markdown document?

easy

A. To run R code and show its output inline with text

B. To write plain text without any code

C. To create a table of contents automatically

D. To add images to the document

Solution

1. Step 1: Understand R Markdown structure

   R Markdown uses code chunks to embed R code inside text documents.

2. Step 2: Purpose of code chunks

   Code chunks run R code and display results inline, mixing code and output.

3. Final Answer:

   To run R code and show its output inline with text -> Option A

4. Quick Check:

   Code chunk = run code + show output [OK]

Hint: Code chunks run code and show output together [OK]

Common Mistakes:

• Thinking code chunks only hold text
• Confusing code chunks with document sections
• Assuming code chunks add images automatically

2. Which of the following is the correct way to start an R code chunk in R Markdown?

easy

A. {r}```

B. ```r

C. ```{r}

D. {r}

Solution

1. Step 1: Recall R Markdown chunk syntax

   R code chunks start with three backticks followed by {r} exactly.

2. Step 2: Check each option

   Only ```{r} correctly starts a chunk; others are invalid syntax.

3. Final Answer:

   ```{r} -> Option C

4. Quick Check:

   Chunk start = ```{r} [OK]

Hint: Start chunks with three backticks and {r} [OK]

Common Mistakes:

• Omitting curly braces around r
• Using only two backticks
• Confusing HTML tags with chunk syntax

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

```{r}
x <- 5
x * 2
```

medium

A. [1] 10

B. 10

C. x * 2

D. Error: object 'x' not found

Solution

1. Step 1: Understand the code execution

   Variable x is assigned 5, then multiplied by 2, resulting in 10.

2. Step 2: R output format

   R prints numeric output with index [1] before the value.

3. Final Answer:

   [1] 10 -> Option A

4. Quick Check:

   5 * 2 = 10 with [1] prefix [OK]

Hint: R prints numeric output with [1] prefix [OK]

Common Mistakes:

• Ignoring the [1] prefix in output
• Expecting just '10' without index
• Thinking code prints the expression itself

4. Identify the error in this R code chunk:

```{r}
print("Hello)
```

medium

A. Missing closing curly brace for chunk

B. Missing closing quote in the string

C. Incorrect function name 'print'

D. No error, code runs fine

Solution

1. Step 1: Check the string syntax

   The string starts with a double quote but lacks the closing double quote.

2. Step 2: Consequence of missing quote

   This causes a syntax error because the string is not properly closed.

3. Final Answer:

   Missing closing quote in the string -> Option B

4. Quick Check:

   Unclosed string causes syntax error [OK]

Hint: Check all quotes are closed in strings [OK]

Common Mistakes:

• Assuming chunk braces cause error
• Thinking print is misspelled
• Ignoring missing quote errors

5. You want to run an R code chunk but hide the code and only show the output. Which chunk option should you use?

hard

A. ```{r, include=FALSE}

B. ```{r, eval=FALSE}

C. ```{r, message=FALSE}

D. ```{r, echo=FALSE}

Solution

1. Step 1: Understand chunk options

   echo=FALSE hides the code but runs it, showing output only.

2. Step 2: Compare other options

   eval=FALSE skips running code, include=FALSE hides both code and output, message=FALSE hides messages only.

3. Final Answer:

   ```{r, echo=FALSE} -> Option D

4. Quick Check:

   echo=FALSE hides code, shows output [OK]

Hint: Use echo=FALSE to hide code but show output [OK]

Common Mistakes:

• Using eval=FALSE hides output too
• Using include=FALSE hides everything
• Confusing message=FALSE with code hiding