Dear all,

I am trying to accomplish a (I think) rather simple task but I just cannot seem to get the desired result. I will try to explain it as clear as possible, show a part of my data, and describe what my desired result is. I hope that you can share your expertise with me on how to accomplish it.

Below, I have data of board directors and in what year they sat on which committee.

Code:
input long DirectorID str38 CommitteeName int Year
1111 "Acquisitions"                          2018
2222 "Audit"                          2018
3333 "Acquisitions"                          2018
5555 "Acquisitions"                          2018
1111 "Acquisitions"                          2019
2222 "Acquisitions"                          2019
3333 "Acquisitions"                          2019
4444 "Acquisitions"                          2019
5555 "Acquisitions"                          2019
 1111 "Acquisitions"            2020
 2222 "Acquisitions"            2020
 3333 "Acquisitions"            2020
 4444 "Acquisitions"            2020
 6666 "Acquisitions"            2020
I want to have a dummy, which displays '1' if the DirectorID has been found earlier in the same committee in the data. With this, I want to indicate if the DirectorID has previous experience in a similar position/committee.

In the first sample year (2018), of course, all then should be assigned a 0 since I do not have data before this time. However, in the data example above and in the year 2019, Directors 1111, 3333, and 5555 should be assigned a '1', since they have previously been in a similar position. Note that Director 2222, although previously found in the data, should not be assigned a 1, since he/she did not sit in the same committee. Also, Director 4444 should not be assigned a '1', since there was no data on him/her in the year 2018. To try and make it clearer, in the year 2020 directors 1111, 2222, 3333, and 4444 should be assigned a '1', since they all sat on the same committee previously. Director 6666 should be assigned a 0, since we did not yet see this director in the data and similar committee.

Does anybody have an idea how to do this? If it is not clear, please let me know. I will then try to clarify this as much as possible.

Thank you for your time and efforts.

Best regards,
Marc