arrange() for sorting in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sort the data frame df by the column age in ascending order using arrange().

R Programming

library(dplyr)
sorted_df <- df %>% arrange([1])
print(sorted_df)

Drag options to blanks, or click blank then click option'

Aage

Bdesc(age)

Cage()

Dsort(age)

Attempts:

3 left

💡 Hint

Common Mistakes

Using desc(age) which sorts in descending order.

Using age() which is not a valid function here.

The arrange() function sorts the data frame by the specified column. Using age sorts it in ascending order.

2fill in blank

medium

Complete the code to sort the data frame df by the column score in descending order using arrange().

R Programming

library(dplyr)
sorted_df <- df %>% arrange([1])
print(sorted_df)

Drag options to blanks, or click blank then click option'

Ascore

Bscore()

Cdesc(score)

Dsort(score)

Attempts:

3 left

💡 Hint

Common Mistakes

Using just score which sorts ascending.

Using score() which is invalid.

To sort in descending order, wrap the column name with desc() inside arrange().

3fill in blank

hard

Fix the error in the code to correctly sort df by height in ascending order.

R Programming

library(dplyr)
sorted_df <- df %>% arrange([1])
print(sorted_df)

Drag options to blanks, or click blank then click option'

Aheight

Bheight()

Cdesc(height)

Dsort(height)

Attempts:

3 left

💡 Hint

Common Mistakes

Using height() which is not valid syntax.

Using desc(height) which sorts descending.

The correct way to sort ascending is to use the column name directly without parentheses or functions.

4fill in blank

hard

Fill both blanks to sort df first by age ascending, then by score descending.

R Programming

library(dplyr)
sorted_df <- df %>% arrange([1], [2])
print(sorted_df)

Drag options to blanks, or click blank then click option'

Aage

Bdesc(score)

Cscore

Ddesc(age)

Attempts:

3 left

💡 Hint

Common Mistakes

Using score instead of desc(score) for descending order.

Using desc(age) which reverses the first sort.

Use age for ascending sort first, then desc(score) for descending sort second.

5fill in blank

hard

Fill all three blanks to sort df by gender ascending, then age descending, then score ascending.

R Programming

library(dplyr)
sorted_df <- df %>% arrange([1], [2], [3])
print(sorted_df)

Drag options to blanks, or click blank then click option'

Agender

Bdesc(age)

Cscore

Ddesc(score)

Attempts:

3 left

💡 Hint

Common Mistakes

Using desc(score) instead of score for ascending order.

Not using desc() for age to get descending order.

Sort by gender ascending, then age descending using desc(age), then score ascending.

Practice

1. What does the arrange() function do in R's dplyr package?

easy

A. Adds new columns to a data frame

B. Filters rows based on a condition

C. Removes duplicate rows from a data frame

D. Sorts rows of a data frame by specified columns

Solution

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

   The arrange() function is used to reorder rows in a data frame based on one or more columns.

2. Step 2: Compare with other functions

   Functions like filter() select rows, mutate() adds columns, and distinct() removes duplicates, so they are different.

3. Final Answer:

   Sorts rows of a data frame by specified columns -> Option D

4. Quick Check:

   arrange() = Sort rows [OK]

Hint: arrange() always changes row order by columns [OK]

Common Mistakes:

• Confusing arrange() with filter()
• Thinking arrange() adds or removes columns
• Assuming arrange() removes duplicates

2. Which of the following is the correct syntax to sort a data frame df by column age in ascending order using arrange()?

easy

A. arrange(df, age)

B. arrange(age, df)

C. arrange(df$age)

D. arrange(df, desc(age))

Solution

1. Step 1: Recall arrange() syntax

   The correct syntax is arrange(data_frame, column_name) to sort by that column ascending.

2. Step 2: Check each option

   arrange(df, age) uses arrange(df, age) which is correct. arrange(age, df) reverses arguments, which is wrong. arrange(df$age) passes a vector, not a data frame. arrange(df, desc(age)) sorts descending, not ascending.

3. Final Answer:

   arrange(df, age) -> Option A

4. Quick Check:

   arrange(data, column) = correct syntax [OK]

Hint: First argument is data frame, second is column name [OK]

Common Mistakes:

• Swapping data frame and column arguments
• Passing column vector instead of data frame
• Using desc() for ascending sort

3. Given the data frame df <- data.frame(name = c('Anna', 'Bob', 'Cara'), score = c(88, 95, 90)), what is the output of arrange(df, desc(score))?

medium

A. Rows sorted by score ascending: Anna, Cara, Bob

B. Rows sorted by score descending: Bob, Cara, Anna

C. Rows sorted by name alphabetically: Anna, Bob, Cara

D. Error because desc() cannot be used inside arrange()

Solution

1. Step 1: Understand desc() inside arrange()

   Using desc(score) sorts the data frame by score in descending order (highest first).

2. Step 2: Apply sorting to given data

   Scores are Anna=88, Bob=95, Cara=90. Descending order is Bob (95), Cara (90), Anna (88).

3. Final Answer:

   Rows sorted by score descending: Bob, Cara, Anna -> Option B

4. Quick Check:

   desc() sorts descending = Bob first [OK]

Hint: desc() reverses sort order inside arrange() [OK]

Common Mistakes:

• Thinking desc() sorts ascending
• Confusing sorting by name vs score
• Believing desc() causes error

4. What is wrong with this code snippet?

arrange(df, desc(age))

where df has no column named age.

medium

A. It will cause an error because age column does not exist

B. It will ignore desc() and sort ascending

C. It will sort by another column automatically

D. It will sort rows by age as NA values

Solution

1. Step 1: Check column existence in arrange()

   arrange() requires the column to exist in the data frame to sort by it.

2. Step 2: Behavior when column missing

   If the column age is missing, R will throw an error indicating the column is not found.

3. Final Answer:

   It will cause an error because age column does not exist -> Option A

4. Quick Check:

   Missing column in arrange() = error [OK]

Hint: arrange() needs existing columns; missing causes error [OK]

Common Mistakes:

• Assuming arrange() ignores missing columns
• Expecting automatic fallback to other columns
• Thinking NA values are sorted without error

5. You have a data frame df with columns city and temperature. How do you sort df first by city alphabetically ascending, then by temperature descending within each city?

hard

A. arrange(df, desc(city), temperature)

B. arrange(df, desc(city), desc(temperature))

C. arrange(df, city, desc(temperature))

D. arrange(df, temperature, city)

Solution

1. Step 1: Understand multi-column sorting with arrange()

   arrange() sorts by columns in the order given. First column sorts primary, second column breaks ties.

2. Step 2: Apply sorting order to columns

   We want city ascending (default) and temperature descending, so use desc(temperature) after city.

3. Final Answer:

   arrange(df, city, desc(temperature)) -> Option C

4. Quick Check:

   Primary city asc, secondary temp desc = arrange(df, city, desc(temperature)) [OK]

Hint: List columns in order; use desc() for descending columns [OK]

Common Mistakes:

• Reversing city sorting with desc() incorrectly
• Sorting temperature ascending instead of descending
• Changing order of columns in arrange()