The pivot_longer() function from the tidyr package in R can be used to pivot a data frame from a wide format to a long format.
This function uses the following basic syntax:
library(tidyr)
df %>% pivot_longer(cols=c('var1', 'var2', ...),
names_to='col1_name',
values_to='col2_name')
where:
- cols: The names of the columns to pivot
- names_to: The name for the new character column
- values_to: The name for the new values column
The following example shows how to use this function in practice.
Related: Long vs. Wide Data: What’s the Difference?
Example: Use pivot_longer() in R
Suppose we have the following data frame in R that shows the number of points scored by various basketball players in different years:
#create data frame df frame(player=c('A', 'B', 'C', 'D'), year1=c(12, 15, 19, 19), year2=c(22, 29, 18, 12)) #view data frame df player year1 year2 1 A 12 22 2 B 15 29 3 C 19 18 4 D 19 12
We can use the pivot_longer() function to pivot this data frame into a long format:
library(tidyr)
#pivot the data frame into a long format
df %>% pivot_longer(cols=c('year1', 'year2'),
names_to='year',
values_to='points')
# A tibble: 8 x 3
player year points
1 A year1 12
2 A year2 22
3 B year1 15
4 B year2 29
5 C year1 19
6 C year2 18
7 D year1 19
8 D year2 12
Notice that the column names year1 and year2 are now used as values in a new column called “year” and the values from these original columns are placed into one new column called “points.”
The final result is a long data frame.
Note: You can find the complete documentation for the pivot_longer() function here.
Additional Resources
The following tutorials explain how to use other common functions in the tidyr package in R:
How to Use pivot_wider() in R
How to Use Spread Function in R
How to Use Gather Function in R
How to Use Separate Function in R
How to Use the Unite Function in R