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st: RE: adding count variables


From   "Fitzmaurice, Ann E." <a.e.fitzmaurice@abdn.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: adding count variables
Date   Wed, 4 Jul 2007 21:40:58 +0100

thsnks nick
 
will play with this, sorry re terminology, normally do data manip in spss, but in this instance need parallel 'syntax' in both spss and stata (have managed the first three syntax files, and the counting variables are the final ) before analysis
 
just a quick question
in spss can stack two data sets with an identid-ier 1 and 2, have a count variable on some events but only in the  the section of the file (coded 1) and after the procedure (in this case poisson regression) , the coefficients are assigned to the other section of the data set, is this possible in stata, or do you run againgst data set a and then use the predict against dataset 2 (as two seperate data sets)
 
if you do not feel that it is appropriate to answer please ignore and i will test this out tomorrow
 
thanks again 
 
ann
 
 
Ann E Fitzmaurice

Medical Statistician
Immpact ,University of Aberdeen
Health Sciences Building
Foresterhill
Aberdeen, AB25 2ZD
Scotland

Tel: +44 (0)1224 553876 

 Fax: +44 (0)1224 555704

Email:  <mailto:a.e.fitzmaurice@abdn.ac.uk <mailto:a.e.fitzmaurice@abdn.ac.uk> > a.e.fitzmaurice@abdn.ac.uk



________________________________

From: owner-statalist@hsphsun2.harvard.edu on behalf of Nick Cox
Sent: Wed 04/07/2007 20:36
To: statalist@hsphsun2.harvard.edu
Subject: st: RE: adding count variables



Whether or not this is quite your problem, this may help.

-collapse- and -contract- are not advisable here, as they
lead to reduced datasets. I guess that you want these characteristics
stored with the individual-level observations.

Suppose you have

familyid    personid  alive (1: alive, 0: dead)

1               1       0
1               2       0
1               3       0
1               4       1
1               5       1
1               6       1
2               7       0
2               8       0 
2               9       1
2              10       1
2              11       1
3              12       1
3              13       1
3              14       1
3              15       1

The number of dead people in each family is

egen n_dead = total(alive == 0), by(familyid)

The number of alive people in each family is

egen n_alive = total(alive == 1), by(familyid)

In addition, use of Stata terminology is advisable
on Statalist. "case" means "observation" in Stata.

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

Ann E Fitzmaurice

> Have a data set with approx 22500 cases from n families, i
> want to create a
> variable wuich is the number of family members in each
> family, variable
> identification is caseid. The data set includes a second
> variable denoting
> the status of the person  , either alive or dead
>
> What I want to do is to put a variable in the file which
> denotes the number
> within a family for the dead people, for example if there are
> six siblings,
> and 3 are dead , then the first variable will gave a 6 next
> to each member
> and a 3 against each member denoting the number dead within a family
>
> From her it is straight forward to calculate the number of
> siblings within a
> family still alive and then make an adjustment to the number
> of women alive
> to reflect that there has been a death in the family
>
> Can anyone suggest how this might be done
>
> I have looked at collapse , and calculated the total within
> the family using
> _N

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