how to use pivot_longer() in R?

In data analysis, it’s common to encounter datasets that need reshaping to make them suitable for analysis or visualization. The tidyr package in R provides convenient functions for transforming your data. One such function is pivot_longer(), which is used to convert data from wide format to long format.

what is wide and long format?

Wide format:

| ID | Jan | Feb | Mar |
|----|-----|-----|-----|
| 1  | 10  | 20  | 30  |
| 2  | 15  | 25  | 35  |

Long format:

| ID | Month | Value |
|----|-------|-------|
| 1  | Jan   | 10    |
| 1  | Feb   | 20    |
| 1  | Mar   | 30    |
| 2  | Jan   | 15    |
| 2  | Feb   | 25    |
| 2  | Mar   | 35    |

using pivot_longer()

Let’s use the following example data frame in wide format:

library(tidyverse)

data <- data.frame(ID = c(1, 2),
                   Jan = c(10, 15),
                   Feb = c(20, 25),
                   Mar = c(30, 35))

print(data)

  ID Jan Feb Mar
1  1  10  20  30
2  2  15  25  35

Use pivot_longer() to transform the data. The function has several parameters, but the most crucial ones are:

• cols: specifies the columns to pivot into longer format.
• names_to: The name of the new key column.
• values_to: The name of the new value column.

long_data <- data %>% 
  pivot_longer(cols = Jan:Mar,
               names_to = "month",
               values_to = "value")

print(long_data)

# A tibble: 6 × 3
     ID month value
  <dbl> <chr> <dbl>
1     1 Jan      10
2     1 Feb      20
3     1 Mar      30
4     2 Jan      15
5     2 Feb      25
6     2 Mar      35