Dear all,

Thanks in advance for any suggestions and supports!
I am currently working on a dataset with three variables that looks like the following

group year id
1 2000 1
1 2000 2
1 2001 5
2 2007 1
2 2007 3
2 2008 4
2 2010 5
This dataset contains random records of ids in different groups at different years. I am hoping to expand the dataset to track the historical ids (of all previous years) of groups in each year.
The new data structure should ideally look like the following
group year id
1 2000 1
1 2000 2
1 2001 1
1 2001 2
1 2001 5
2 2007 1
2 2007 3
2 2008 1
2 2008 3
2 2008 4
2 2010 1
2 2010 3
2 2010 4
2 2010 5

I have tried to use suggestions from this link: https://stats.idre.ucla.edu/stata/fa...time-variable/.
However, my dataset is not exactly a panel dataset. Does anyone have suggestions for this issue? I would appreciate any advice.
This question is cross-posted in the Mata forum too.