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# st: RE: how to calculate cumulative number of organizations for stcox?

 From Nick Cox To "'statalist@hsphsun2.harvard.edu'" Subject st: RE: how to calculate cumulative number of organizations for stcox? Date Wed, 15 Jun 2011 22:55:03 +0100

```Have a look at

FAQ     . . . . . . . . . . . . . .  Calculating the number of distinct values
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
9/06    How do I calculate the number of distinct
values seen so far?
http://www.stata.com/support/faqs/data/distinctvalues.html

Nick
n.j.cox@durham.ac.uk

Caleb Southworth

My data include a continuous date and organizations. How can I
calculate the cumulative number of organizations in existence at time
t?

I could do this by year. My strategy at present it to calculate the
survival interval for h(t_i-t). I would like to calculate the number
of organizations in existence at the beginning of that interval.
Thanks!--Caleb

. stset date, id(id) fail(found==0)

id:  id
failure event:  found == 0
obs. time interval:  (date[_n-1], date]
exit on or before:  failure

------------------------------------------------------------------------------
621  total obs.
565  obs. end on or before enter()
------------------------------------------------------------------------------
56  obs. remaining, representing
56  subjects
18  failures in single failure-per-subject data
212648  total analysis time at risk, at risk from t =         0
earliest observed entry t =         0
last observed exit t =      8294

.
end of do-file

. stdes

failure _d:  found == 0
analysis time _t:  date
id:  id

|-------------- per subject --------------|
Category                   total        mean         min     median        max
------------------------------------------------------------------------------
no. of subjects               56
no. of records                56           1           1          1          1

(first) entry time                         0           0          0          0
(final) exit time                   3797.286           1       3925       8294

subjects with gap              0
time on gap if gap             0           .           .          .          .
time at risk              212648    3797.286           1       3925       8294

failures                      18    .3214286           0          0          1
------------------------------------------------------------------------------

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```

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