I am trying to solve something that for me is a problem since a few days.

Here an example of my data.frame, which I hope will work with my real one.

```
df <- read.table(text = 'ID    Day Count
    33012   9526    4
    35004   9526    4
    37006   9526    4
    37008   9526    4
    21009   1913    3
    24005   1913    3
    25009   1913    3
    22317   2286    2
    37612   2286    2
    25009   14329   1
    48007   9525    0
    88662   9524    0
    1845    9524    0
    8872    2285    0
    49002   1912    0
    1664    1911    0', header = TRUE)

```

I need to add a new column (`new_col`) to my data.frame which contains values from 1 to 4. These `new_col` values have to include, each one, day (x) day (x -1) and day (x -2), where x = 9526, 1913, 2286, 14329 (column `Day`).

My output should be the following:

```
   ID    Day Count  new_col
33012   9526    4     1
35004   9526    4     1
37006   9526    4     1
37008   9526    4     1
21009   1913    3     2
24005   1913    3     2
25009   1913    3     2
22317   2286    2     3
37612   2286    2     3
25009   14329   1     4
48007   9525    0     1
88662   9524    0     1
1845    9524    0     1
8872    2285    0     3
49002   1912    0     2
1664    1911    0     2

```

The data.frame ordered by `new_col` will be then:

```
   ID    Day Count  new_col
33012   9526    4     1
35004   9526    4     1
37006   9526    4     1
37008   9526    4     1
48007   9525    0     1
88662   9524    0     1
1845    9524    0     1
21009   1913    3     2
24005   1913    3     2
25009   1913    3     2
49002   1912    0     2
1664    1911    0     2
22317   2286    2     3
37612   2286    2     3
8872    2285    0     3
25009   14329   1     4

```

My real data.frame is more complex than the example (i.e. more columns and more values in the `Count` column, therefore be patient if I will update the question.

Any suggestion will be really helpful.