st: generating a variable that requires comparing two dates

["Ariel Linden, DrPH" <ariel.linden@gmail.com>]

Hi fellow listers,

This may be an easy task, but I am not getting it right...

I would like to generate a new variable ( by ID) that will equal 1 if there
was an alert (triggered on the surveydate, when that surveydate was the same
as the admitdate. The obvious problem is that the dates are not always
aligned so a straight "bys ID: gen test if surveydate==admitdate & alert==1"
will not always work.

In the data below, the code would need to "see" that the admitdate of
4/6/2011 has a corresponding surveydate a few lines down where the alert==1.
Similarly, the next admitdate is 4/20/2011, so it would need to lookup the
corresponding surveydate and verify that alert==1.

I would then like to run this code again (generating a new variable) where
we'd look to see if there was an alert on the surveydate the day before the
admitdate (ie., surveydate = admitdate - 1)

Thanks in advance!

Ariel

**** example data****

ID	surveydate	alert	admitdate
1	4/2/2011	1	4/6/2011
1	4/3/2011	1	4/20/2011
1	4/4/2011	0	4/20/2011
1	4/5/2011	0	4/20/2011
1	4/6/2011	1	4/20/2011
1	4/7/2011	0	4/20/2011
1	4/8/2011	0	4/20/2011
1	4/9/2011	0	4/20/2011
1	4/10/2011	0	4/20/2011
1	4/11/2011	0	4/20/2011
1	4/12/2011	0	4/20/2011
1	4/13/2011	0	4/20/2011
1	4/14/2011	0	4/20/2011
1	4/15/2011	0	4/20/2011
1	4/16/2011	0	4/20/2011
1	4/17/2011	0	4/20/2011
1	4/18/2011	0	4/20/2011
1	4/19/2011	0	4/20/2011
1	4/20/2011	1	4/20/2011
1	4/21/2011	0	4/20/2011
*************************************

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