rdataframerep

Group column by regular interval


I'm struggling to solve a seemingly simple task. In this type of data:

df <- data.frame(
  A = c(1,2,3,4,1,2,3,2,2,2,2,1,1,1,1,6,7)
)

I want to add an id variable that groups column A by a regular interval, say, of 5. An additional difficulty is that the number of rows is 17, thus not a multiple of 5:

df <- data.frame(
  A = c(1,2,3,4,1,2,3,2,2,2,2,1,1,1,1,6,7),
  id = c("a","a","a","a","a", 
         "b","b","b","b","b",
         "c","c","c","c","c",
         "d","d"))

How can this be done?


Solution

  • A possible solution:

    library(dplyr)
    
    df <- data.frame(
      A = c(1,2,3,4,1,2,3,2,2,2,2,1,1,1,1,6,7)
    )
    
    df %>% 
      mutate(id = rep(letters, each=5)[1:n()])
    
    #>    A id
    #> 1  1  a
    #> 2  2  a
    #> 3  3  a
    #> 4  4  a
    #> 5  1  a
    #> 6  2  b
    #> 7  3  b
    #> 8  2  b
    #> 9  2  b
    #> 10 2  b
    #> 11 2  c
    #> 12 1  c
    #> 13 1  c
    #> 14 1  c
    #> 15 1  c
    #> 16 6  d
    #> 17 7  d