st: Keeping specific observations

[Eleimon Gonis <Eleimon2.Gonis@uwe.ac.uk>]

Dear Statalisters,

I would appreciate your help with the following conundrum. Assume I have a dataset that looks like this:

Year         ID        v1
2000         1          2
2001         1          2
2002         1          3
2000         2          3
2001         2          .
2002         2          3
2000         3          .
2001         3          .
2002         3          .

What I want to achieve is to only keep those individuals that appear with any non-missing values for v1 for any of the years in the dataset.

In other words, I don't think that a command: "keep if v1<." would do, because that would also take out the 2001 observation for the second individual (ID==2), which I'd like to remain in place.

Any ideas are welcome,
Eleimon

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/