R dplyr cumulative difftime with condition

Question

lets say I have dataframe like this:

dt <-
  data.frame(
    date = as.Date(
      c("2022-01-01", "2022-01-03", "2022-01-05", "2022-01-06", "2022-01-07", "2022-02-01", "2022-02-01"))
  )

I would like to calculate sequence of dates, where difftime between first in sequence and last is less or equal 2 days. Once sequence reaches its last possible day, I would like to create seqeuences from all upcoming ones.

In other words: Dataset and even sequence starts with 2022-01-01 so it will be marked by 0 - 2022-01-03 will be marked by 1 because it is part of sequence that started on 2022-01-01.

2022-01-05 can't be marked by 0 because difftime between 2022-01-01 and 2022-01-05 is greater than 2 days, this date is begining of new sequence and all upcoming dates where difftime is lower or equeal than 2 days (2022-01-06 and 2022-01-07) will be marked by 0.

Simiarly with 2022-02-01 (please note than there could be same dates in dataset).

I prefer dplyr solution, but if you can create another one, help I really appreciate your help.

result <-
  data.frame(
    date = as.Date(
      c("2022-01-01", "2022-01-03", "2022-01-05", "2022-01-06", "2022-01-07", "2022-02-01", "2022-02-01")),
    flag = c(0, 1, 1, 0, 0, 1, 0)
  )

Answer 1

We may use diff to get the difference between adjacent 'date' and convert it to logical vector ( > ) and coerce the logical to binary with + or as.integer

library(dplyr)
dt <- dt %>% 
   mutate(flag = +(c(0, diff(date) >  1)))

-output

dt
       date flag
1 2022-01-01   0
2 2022-01-03   1
3 2022-01-05   1
4 2022-01-06   0
5 2022-01-07   0
6 2022-02-01   1
7 2022-02-01   0

---

Or with lag and difftime

dt %>% 
 mutate(flag = +(difftime(date, lag(date, default = first(date)),
      units = "day") > 1))
        date flag
1 2022-01-01    0
2 2022-01-03    1
3 2022-01-05    1
4 2022-01-06    0
5 2022-01-07    0
6 2022-02-01    1
7 2022-02-01    0