st: date of last follow up

[Michael Eisenberg <meisenberg713@gmail.com>]

Colleagues,

I'd like some help working with dates in Stata.

I have a list of visits for several patients.  I'd like to make a
column which lists the date they were last seen.  In other words, a
date of last follow up.

I'm fairly certain I need to start with a bysort command, but I'm not
sure what should come next.

My data looks as follows.

subjectid   test      visitdate
1                r            1-3-2010
1                q            2-1-2009
1                e            6-3-2011
2                q            2-1-2006
2                e            6-3-2008
3               r              1-3-2005
4                q            2-26-2009
4                e            6-13-2011
4                r             10-23-2010
2                q            2-15-2007
1                e            6-30-2004

Thank you in advance.

Mike
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