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st: generating a moving sum


From   Alexander Tsai <act2@cwru.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: generating a moving sum
Date   Fri, 21 Nov 2003 20:19:33 -0500

Dear Statalisters,

I have a dataset of hospital admissions: admissions indexed by
"admitid", patients indexed by "ptid", hospitals indexed by "hospid".

       +-------------------------------------------+
       |   doadmit   admitid         ptid   hospid |
       |-------------------------------------------|
    1. | 21 Jun 91       160       007336        1 |
    2. | 23 Jun 91       197       007695        1 |
    3. | 28 Jun 91       419       126888        1 |
    4. | 30 Jun 91       550       046134        1 |
    5. | 02 Jul 91       696       015142        1 |
       |-------------------------------------------|
    6. | 03 Jul 91       771       035194        1 |
    7. | 05 Jul 91       906       006762        1 |
    8. | 06 Jul 91       989       114879        1 |
    9. | 07 Jul 91      1040       010445        1 |
   10. | 11 Jul 91      1328       035194        1 |
       |-------------------------------------------|
   11. | 12 Jul 91      1403       016055        1 |
   12. | 12 Jul 91      1402       001565        1 |
   13. | 15 Jul 91      1609       007721        1 |
   14. | 16 Jul 91      1694       015450        1 |
   15. | 18 Jul 91      1856       005970        1 |
       |-------------------------------------------|
	 |			etc...			   |

What I would like to do is this: for each patient-admission, calculate
the total number of admissions at that hospital in the prior 90 days.

On Sep 3 '03, Kristien Verheyen posted a message to the listserv
(subject: "Generating 'moving sum' variable") that had to do with
calculating moving sums, but my data are a little more complicated. My
first thought was to expand the data with dummy dates of admission and
generate moving sums by the prior 90 rows, but then I run into the
problem that some hospitals have multiple admissions on one day.

Does anyone have any suggestions?
Thank you.

Alex Tsai



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