How can I replace values in R data frame by their categories?

Question

Consider e.g. the following data frame:

data <- matrix(c(12, 6, 13, 15, 2, 7, 7, 14), nrow = 4)
data <- as.data.frame(data)

Variable 1	Variable 2
12	2
6	7
13	7
15	14

Suppose that the values of the Variable 2 are instances of two categories; category 1 (values < 10) and category 2 (values >= 10).

How could I replace the second column by the category of its value? The resulting data frame would be:

Variable 1	Variable 2 (Category)
12	Category 1
6	Category 1
13	Category 1
15	Category 2

Use the base function `cut`, it works with whatever number of breaks you need — camille, Feb 26 '23 at 02:12

score 1 · Answer 1 · answered Feb 25 '23 at 21:44

1

library(tidyverse) 

data %>% 
  mutate(across(V2, ~ if_else(.x >= 10, "Category 2", "Category 1")))

     V1 V2        
  <dbl> <chr>     
1    12 Category 1
2     6 Category 1
3    13 Category 1
4    15 Category 2

answered Feb 25 '23 at 21:44

Chamkrai

5,912
1
4
14

Thanks. Do you know any easy way to do that if I had more than two categories, say, 10 categories? – mathslover Feb 25 '23 at 21:46

score 0 · Answer 2 · answered Feb 26 '23 at 00:16

alternatively with data.table

library(data.table)

data <- matrix(c(12, 6, 13, 15, 2, 7, 7, 14), nrow = 4)
data <- as.data.table(data)

format_cat <- function(x){
  case_when(
  x < 10 ~ 'Category 1',
  x >=10 ~ 'Category 2'
  )
}

data[, V2 := format_cat(V2)]

^{Created on 2023-02-25 with reprex v2.0.2}

   V1         V2
1: 12 Category 1
2:  6 Category 1
3: 13 Category 1
4: 15 Category 2

How can I replace values in R data frame by their categories?

2 Answers2