How to add a column that identifies groups of consecutive days

In a data.frame, I would like to add a column that identifies groups of consecutive days.

I think I need to start by converting my strings to date format…

Here’s my example :

mydf <- data.frame(
  var_name = c(rep("toto",6),rep("titi",5)),
  date_collection = c("09/12/2022","10/12/2022","13/12/2022","16/12/2022","16/12/2022","17/12/2022",
                      "01/12/2022","03/11/2022","04/11/2022","05/11/2022","08/11/2022")
)

Expected output :

>Solution :

Convert to Date class and do the adjacent diff to create a a logical vector and take the cumulative sum

library(dplyr)
library(lubridate)
mydf %>%
    mutate(id = cumsum(c(0, abs(diff(dmy(date_collection)))) > 1)+1)