pivot_longer (wide to long) in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the pivot_longer() function do in R?

It transforms data from a wide format (many columns) into a long format (fewer columns, more rows), making it easier to analyze and visualize.

beginner

In pivot_longer(), what do the cols and names_to arguments specify?

cols selects which columns to turn from wide to long. names_to names the new column that will hold the old column names.

intermediate

Why would you use pivot_longer() instead of keeping data wide?

Long format data is easier to work with for many R functions and plotting tools because it standardizes the structure, making grouping and summarizing simpler.

beginner

What happens if you omit the values_to argument in pivot_longer()?

The new column holding the values from the original columns will be named value by default.

intermediate

How can you use pivot_longer() to reshape this data?<br>

  id  Jan  Feb  Mar
1  A   10   20   30
2  B   15   25   35

Use pivot_longer(cols = Jan:Mar, names_to = "month", values_to = "value") to get columns id, month, and value with one row per month per id.

What is the main purpose of pivot_longer() in R?

A Filter rows based on a condition

B Convert wide data to long format

C Convert long data to wide format

D Sort data by column values

pivot_longer() changes wide data (many columns) into long data (fewer columns, more rows).

Which argument in pivot_longer() specifies the new column name for the old column names?

A names_to

B cols

C values_to

D values_drop_na

names_to sets the name of the new column that holds the original column names.

If you want to keep columns id and reshape columns Q1, Q2, Q3, which cols argument would you use?

A cols = id

B cols = NULL

C cols = Q1:Q3

D cols = everything()

cols = Q1:Q3 selects columns Q1 to Q3 to pivot longer.

What default name does pivot_longer() give to the values column if values_to is not set?

A value

B values

C data

D val

The default name for the values column is value.

Which package provides the pivot_longer() function?

A data.table

B dplyr

C ggplot2

D tidyr

pivot_longer() is part of the tidyr package.

Explain in your own words what pivot_longer() does and why it is useful.

Think about changing many columns into fewer columns with more rows.

Describe how you would use pivot_longer() to reshape a dataset with monthly sales columns into a long format with one column for month and one for sales.

Focus on naming the new columns for months and sales values.