repeating a number n times, then a different number for the remainder of the rows in R

Question

I have a dataset where each row is a monthly observation of patients, monitoring whether they tested positive to a disease (status).

I know which month (i.e. row number for each ID - TimeToDx) they were diagnosed, and what I would like to do is have a binary indicator that switches from 0 to 1, starting from the observation month indicated in TimeToDx.

Basically I need to replicate 0 by the TimeToDx - 1, then for the remainder of the rows replicate 1 for each ID.

Here is some example data - without the status indicator filled:

 ID TimeToDx    Status
10425   2   
10425   2   
10425   2   
10425   2   
10667   3   
10667   3   
10667   3   
10667   3   
10667   3   
10686   2   
10686   2   
10686   2   
10686   2   
10686   2   
17096   5   
17096   5   
17096   5   
17096   5   
17096   5   

Here is what I would like to see:

ID  TimeToDx    Status
10425   2       0
10425   2       1
10425   2       1
10425   2       1
10667   3       0
10667   3       0
10667   3       1
10667   3       1
10667   3       1
10686   2       0
10686   2       1
10686   2       1
10686   2       1
10686   2       1
17096   5       0
17096   5       0
17096   5       0
17096   5       0
17096   5       1

Any help would be much appreciated.

Answer 1

df <- structure(list(ID = c(10425L, 10425L, 10425L, 10425L, 10667L, 
                            10667L, 10667L, 10667L, 10667L, 10686L, 10686L, 10686L, 10686L, 
                            10686L, 17096L, 17096L, 17096L, 17096L, 17096L), 
                     TimeToDx = c(2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 2L, 2L,
                                  2L, 2L, 2L, 5L, 5L, 5L, 5L, 5L)),
                class = "data.frame", row.names = c(NA, -19L))

library(tidyverse)
df %>%
  group_by(ID) %>% 
  mutate(Status = +((row_number() %/% TimeToDx) != 0)) %>% 
  ungroup()
#> # A tibble: 19 x 3
#>       ID TimeToDx id_row
#>    <int>    <int>  <int>
#>  1 10425        2      0
#>  2 10425        2      1
#>  3 10425        2      1
#>  4 10425        2      1
#>  5 10667        3      0
#>  6 10667        3      0
#>  7 10667        3      1
#>  8 10667        3      1
#>  9 10667        3      1
#> 10 10686        2      0
#> 11 10686        2      1
#> 12 10686        2      1
#> 13 10686        2      1
#> 14 10686        2      1
#> 15 17096        5      0
#> 16 17096        5      0
#> 17 17096        5      0
#> 18 17096        5      0
#> 19 17096        5      1

^{Created on 2021-10-21 by the reprex package (v2.0.1)}

data.table

using @Jon Spring's solution

library(data.table)
setDT(df)[, Status := +(rowid(ID) >= TimeToDx)][]
#>        ID TimeToDx Status
#>  1: 10425        2      0
#>  2: 10425        2      1
#>  3: 10425        2      1
#>  4: 10425        2      1
#>  5: 10667        3      0
#>  6: 10667        3      0
#>  7: 10667        3      1
#>  8: 10667        3      1
#>  9: 10667        3      1
#> 10: 10686        2      0
#> 11: 10686        2      1
#> 12: 10686        2      1
#> 13: 10686        2      1
#> 14: 10686        2      1
#> 15: 17096        5      0
#> 16: 17096        5      0
#> 17: 17096        5      0
#> 18: 17096        5      0
#> 19: 17096        5      1

^{Created on 2021-10-21 by the reprex package (v2.0.1)}