filter data use different group

[Han Jin]

----------------------- copy starting from the next line -----------------------

* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id month change)
1  1 .
1  2 .
1  3 .
1  4 .
1  5 .
1  6 6
1  7 .
1  8 .
1  9 .
1 10 .
1 11 .
1 12 .
2  1 .
2  2 .
2  3 .
2  4 .
2  5 .
2  6 .
2  7 7
2  8 .
2  9 .
2 10 .
2 11 .
2 12 .
end

------------------ copy up to and including the previous line ------------------

I want to keep data in every id when month > change, for example id 1 , change is 6 , then I want to result output month in ID 1 : 7 8 910 11 12


so many thanks

[William Lisowski]

Perhaps this will start you in a useful direction.

. bysort id (month): egen tokeep = min(change+1)

. drop if month<tokeep
(13 observations deleted)

. list, noobs sepby(id)

  +------------------------------+
  | id   month   change   tokeep |
  |------------------------------|
  |  1       7        .        7 |
  |  1       8        .        7 |
  |  1       9        .        7 |
  |  1      10        .        7 |
  |  1      11        .        7 |
  |  1      12        .        7 |
  |------------------------------|
  |  2       8        .        8 |
  |  2       9        .        8 |
  |  2      10        .        8 |
  |  2      11        .        8 |
  |  2      12        .        8 |
  +------------------------------+

[Han Jin]

Perhaps this will start you in a useful direction.

. bysort id (month): egen tokeep = min(change+1)

. drop if month<tokeep
(13 observations deleted)

. list, noobs sepby(id)

+------------------------------+
| id month change tokeep |
|------------------------------|
| 1 7 . 7 |
| 1 8 . 7 |
| 1 9 . 7 |
| 1 10 . 7 |
| 1 11 . 7 |
| 1 12 . 7 |
|------------------------------|
| 2 8 . 8 |
| 2 9 . 8 |
| 2 10 . 8 |
| 2 11 . 8 |
| 2 12 . 8 |
+------------------------------+

Thank you so much William!