Dear Statalist,

Here is an example of my data, two of its variables are CaseID and Surveyyear:
CaseID Surveyyear
1 2004
1 2004
1 2004
2 1999
2 1999
2 1999
2 2000
2 2000
2 2000
3 2002
3 2002
3 2009
3 2010
3 2010
For each group of caseID that has more than 1 value of Surveyyear, I want to keep observations that have the maximum value of Surveyyear. If there is only 1 value of Surveyyear in a group, I'll keep all of the observations in that group. It means, I want to generate this following result:
CaseID Surveyyear
1 2004
1 2004
1 2004
2 2000
2 2000
2 2000
3 2010
3 2010
Could someone help me? I tried using 'collapse' and, 'keep if _n == _N', but only one observation in each group is kept, not all the observations that have the same value.
Thank you so much in advance.
Best regard,
Cameron.