Inline R code in R Programming - Mini Project: Build & Apply

Using Inline R Code in R Markdown

📖 Scenario: You are preparing a simple R Markdown report to show some basic calculations inline with your text. This helps make your report dynamic and clear.

🎯 Goal: Create an R Markdown snippet that uses inline R code to display the result of a calculation inside a sentence.

📋 What You'll Learn

Create a numeric variable called num_apples with the value 5

Create a numeric variable called num_oranges with the value 3

Create a variable called total_fruits that sums num_apples and num_oranges

Write an R Markdown sentence that uses inline R code to show the value of total_fruits

💡 Why This Matters

🌍 Real World

Inline R code is used in R Markdown reports to show dynamic results inside text, making reports clear and automatically updated.

💼 Career

Data analysts and scientists use inline R code to create professional reports that update calculations automatically when data changes.

1

Create variables for fruit counts

Create a numeric variable called num_apples and set it to 5. Also create a numeric variable called num_oranges and set it to 3.

R Programming

# Create variables num_apples and num_oranges
# Your code here

Hint

Use the assignment operator <- to assign values to variables.

2

Calculate total fruits

Create a variable called total_fruits that adds num_apples and num_oranges.

R Programming

num_apples <- 5
num_oranges <- 3
# Calculate total_fruits by adding num_apples and num_oranges
# Your code here

Hint

Use the + operator to add the two variables.

3

Write an R Markdown sentence with inline code

Write a character string variable called sentence that contains the text: "I have a total of `r total_fruits` fruits." Use backticks and r to include total_fruits inline as in R Markdown.

R Programming

num_apples <- 5
num_oranges <- 3
total_fruits <- num_apples + num_oranges
# Create sentence with inline R code for total_fruits
# Your code here

Hint

Use double quotes for the string and include `r total_fruits` exactly inside.

4

Print the sentence

Use print(sentence) to display the sentence with inline R code.

R Programming

num_apples <- 5
num_oranges <- 3
total_fruits <- num_apples + num_oranges
sentence <- "I have a total of `r total_fruits` fruits."
# Print the sentence
# Your code here

Hint

Use the print() function to show the sentence.

Practice

1. What is the purpose of using inline R code with `r expression` in documents?

easy

A. To comment out code in R scripts

B. To insert the result of an R expression directly into the text

C. To create a new R function

D. To define a variable in R

Solution

1. Step 1: Understand inline R code usage

   Inline R code uses backticks and r to embed R expressions inside text.

2. Step 2: Identify the purpose

   This allows the result of the R expression to appear directly in the document text, making it dynamic.

3. Final Answer:

   To insert the result of an R expression directly into the text -> Option B

4. Quick Check:

   Inline R code = insert R result in text [OK]

Hint: Inline code shows R results inside text using backticks [OK]

Common Mistakes:

• Thinking inline code defines variables
• Confusing inline code with comments
• Believing inline code creates functions

2. Which of the following is the correct syntax for inline R code to show the sum of 2 and 3?

easy

A. `r 2 + 3`

B. `r sum(2 + 3`

C. `r sum 2, 3`

D. `r sum(2,3`

Solution

1. Step 1: Inline R code evaluates expressions

   Inline R code executes the R expression between the backticks and inserts its result (here, 2+3=5).

2. Step 2: Check each option's validity

   `r sum 2, 3` missing parens around args: sum 2 -> sum(2)=2, then ,3 -> 3 (wrong).
   `r sum(2 + 3` missing ) -> syntax error.
   `r 2 + 3` -> 5 (correct).
   `r sum(2,3` missing ) -> syntax error.

3. Final Answer:

   `r 2 + 3` -> Option A

4. Quick Check:

   Simple expression inside `r` is best [OK]

Hint: Use simple expressions inside `r` for inline code [OK]

Common Mistakes:

• Adding extra parentheses inside sum()
• Using incorrect commas or spaces
• Confusing function call syntax

3. What will be the output of this inline R code snippet in a document? `r paste('Hello', 'World')`

medium

A. Error

B. paste('Hello', 'World')

C. HelloWorld

D. Hello World

Solution

1. Step 1: Understand paste() function

   The paste() function joins strings with a space by default, so paste('Hello', 'World') returns "Hello World".

2. Step 2: Inline code outputs the result

   The inline R code evaluates the expression and inserts the result "Hello World" into the document.

3. Final Answer:

   Hello World -> Option D

4. Quick Check:

   paste() joins strings with space [OK]

Hint: paste() joins words with space by default [OK]

Common Mistakes:

• Expecting no space between words
• Thinking inline code shows code, not result
• Confusing paste() with paste0()

4. Identify the error in this inline R code: `r mean(c(1, 2, '3'))`

medium

A. Missing closing backtick

B. mean() cannot take vectors

C. Character '3' causes mean() to fail

D. No error, code runs fine

Solution

1. Step 1: Check vector contents

   The vector c(1, 2, '3') mixes numbers and a character, so R converts all to character.

2. Step 2: mean() expects numeric input

   mean() cannot calculate mean of characters, so it will produce an error.

3. Final Answer:

   Character '3' causes mean() to fail -> Option C

4. Quick Check:

   mean() needs numeric vector [OK]

Hint: mean() needs numeric values, no characters [OK]

Common Mistakes:

• Ignoring type conversion in vectors
• Assuming mean() works on mixed types
• Missing quotes around characters

5. You want to display the number of rows in a data frame df inline in your report. Which inline R code correctly shows this count?

hard

A. `r nrow(df)`

B. `r length(df)`

C. `r df$nrow`

D. `r count(df)`

Solution

1. Step 1: Recall function to get row count

   The function nrow() returns the number of rows in a data frame.

2. Step 2: Check each option

   `r nrow(df)` uses nrow(df) which is correct. `r length(df)` uses length(df) which returns number of columns, not rows. `r df$nrow` tries to access a non-existent column nrow. `r count(df)` uses count() which is not a base R function for this purpose.

3. Final Answer:

   `r nrow(df)` -> Option A

4. Quick Check:

   nrow() gives row count [OK]

Hint: Use nrow() to get rows count inline [OK]

Common Mistakes:

• Using length() for rows instead of columns
• Trying to access nrow as a column
• Using non-base functions without loading packages