arrange() for sorting in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the arrange() function do in R?

The arrange() function sorts rows of a data frame or tibble by one or more columns in ascending order by default.

beginner

How do you sort a data frame by a column descending using arrange()?

Use the desc() function inside arrange() like this: arrange(data, desc(column_name)).

beginner

What package do you need to use arrange()?

You need the dplyr package, which is part of the tidyverse collection.

intermediate

How can you sort by multiple columns using arrange()?

List the columns in order inside arrange(), like arrange(data, col1, col2). It sorts by col1 first, then col2 to break ties.

advanced

What happens if you use arrange() on a grouped tibble?

arrange() sorts the entire data frame ignoring groups unless you use group_by() with arrange() carefully or use slice_min() or slice_max() for group-wise sorting.

What is the default sorting order of arrange() in R?

A No sorting

B Descending

C Ascending

D Random

arrange() sorts data in ascending order by default.

Which package provides the arrange() function?

A dplyr

B ggplot2

C base

D tidyr

arrange() is part of the dplyr package.

How do you sort a data frame by column age in descending order?

A sort(data$age, decreasing = TRUE)

B arrange(data, age)

C arrange(data, -age)

D arrange(data, desc(age))

Use desc() inside arrange() to sort descending.

What happens if you use arrange() with multiple columns?

A Sorts by the first column, then second to break ties

B Sorts only by the last column

C Sorts randomly

D Throws an error

arrange() sorts by columns in the order listed.

Which function is used inside arrange() to sort descending?

A reverse()

B desc()

C decreasing()

D order()

desc() tells arrange() to sort descending.

Explain how to use arrange() to sort a data frame by one or more columns in R.

Think about how you tell R which columns to sort by and how to change the order.

Describe what package you need and how arrange() behaves with grouped data.

Remember tidyverse and grouping concepts.

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()