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

Recall & Review

beginner

What does the pivot_wider() function do in R?

pivot_wider() transforms data from a long format to a wide format by spreading key-value pairs across multiple columns.

beginner

Which package in R provides the pivot_wider() function?

The pivot_wider() function is part of the tidyr package, which helps tidy and reshape data.

beginner

In pivot_wider(), what do the names_from and values_from arguments specify?

names_from specifies the column whose values will become new column names.<br>values_from specifies the column whose values will fill the new columns.

intermediate

Given this long data frame:<br>

df <- data.frame(
  id = c(1,1,2,2),
  key = c('A','B','A','B'),
  value = c(10,20,30,40)
)

<br>What will pivot_wider(df, names_from = key, values_from = value) produce?

  id  A   B
1  1 10  20
2  2 30  40

This spreads the key values A and B into columns, filling with value.

intermediate

How does pivot_wider() handle multiple values for the same id and name combination?

By default, it will give an error if multiple values exist for the same combination.<br>You can use the values_fn argument to specify how to combine them, like list or sum.

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

A Convert data from long to wide format

B Convert data from wide to long format

C Filter rows based on conditions

D Sort data by column values

pivot_wider() changes data from long format to wide format by spreading key-value pairs into columns.

Which argument in pivot_wider() defines the new column names?

A values_from

B id_cols

C cols

D names_from

names_from specifies the column whose values become the new column names.

If you have multiple values for the same id and name in pivot_wider(), what argument helps you handle them?

A values_fill

B values_fn

C names_prefix

D id_cols

values_fn lets you specify a function to combine multiple values, like sum or list.

Which R package must you load to use pivot_wider()?

A tidyr

B ggplot2

C dplyr

D data.table

pivot_wider() is part of the tidyr package.

What will pivot_wider() do if some combinations have missing values?

A Throw an error

B Remove those rows

C Fill with NA by default

D Fill with zero automatically

By default, missing combinations are filled with NA. You can change this with values_fill.

Explain how pivot_wider() transforms a long data frame into a wide one. Include the roles of names_from and values_from.

Think about spreading key-value pairs into columns.

Describe how to handle multiple values for the same id and name combination when using pivot_wider().

Consider what happens if one cell would have many values.