# AW: st: AW: simple sum() question

 From "Martin Weiss" To Subject AW: st: AW: simple sum() question Date Wed, 15 Apr 2009 18:15:08 +0200

```<>
" With Martin's solution, I will need to have four observations for each
patient"

No you do not. It will count whatever you want it to count within
patients...

HTH
Martin

-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Shehzad Ali
Gesendet: Mittwoch, 15. April 2009 17:55
An: statalist@hsphsun2.harvard.edu
Betreff: Re: st: AW: simple sum() question

Hi Martin and Josiane,

Thank you for your replies. You are right that I am interested in the total
count of visits for each patient and not the running sum.

Sorry, I should have mentioned that patients who had three visits, for
instance, have three observations, and those with two visits have two
observations. Therefore, the total number of observations for 100 patients
is less than 400 (I had made up hypothetical numbers in haste to simplify
the case. Not always a good idea).

With Martin's solution, I will need to have four observations for each
patient (sorry this was my fault as I didn't provide the correct
information). With Josiane's suggestion, the dataset collapses which is not
what I want.

Can you suggest a modified solution please? Again, sorry for the unclear
email earlier.

Thank you,

On Apr 15 2009, Martin Weiss wrote:

>
><>
>
> I am betting that you want a count of visits, not a running sum, but
> correct me if I am wrong...
>
>
>*************
>clear*
>set obs 400
>egen float patient = seq(), from(1) to(400) block(4)
>egen float visit = seq(), from(1) to(4) block(1)
>
>//not strictly necessary
>xtset patient visit
>
>//less than 4 visits for some
>replace visit =. if runiform()<0.05
>
>bys patient: egen overallvisits=count(visit)
>
>l in 1/20, sepby(patient) noo
>*************
>
>
>
>HTH
>Martin
>
>
>-----Ursprüngliche Nachricht-----
>Von: owner-statalist@hsphsun2.harvard.edu
>[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Shehzad Ali
>Gesendet: Mittwoch, 15. April 2009 16:48
>An: statalist@hsphsun2.harvard.edu
>Cc: noman.paracha@gmail.com
>Betreff: st: simple sum() question
>
>Hi,
>
>I have a simple question about summing across observations. I have 100
>patients (variable: patient_id) in the dataset, each had clinic visits
>(variable: clinic) and hospital visits (variable: hospital) recorded at
>weeks 4, 8, 12 and 16. The dataset is long and hence I have 400
>observations (one observation per patient per time point).
>
> I want to sum the clinic visits for each patient (across all 4 visits)
> bearing in mind that some patients had less than 4 visits. So effectively
> I want to generate a new variable that will produce the sum of clinic
> visits for each patient.
>
>Any help would be appreciated.
>
>Thank you,
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