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RE: st: multiple observations


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: multiple observations
Date   Thu, 11 Sep 2008 14:25:13 +0100

In general -egen, tag()- is not appropriate and would give incorrect
answers here. 

-egen, tag()- tags just one of a group of duplicated observations. Then
if you had a series of observations identical on x y you might want to
tag just one as otherwise a -scatter- graph file containing the same
information on x and y would be bloated to no purpose. 

In this problem you do not regard observations in a panel as duplicated.
Rather you regard the last observation as special, a quite separate
problem. 

-egen, tag()- would give you exactly the right answer if and only if
each panel occurred just once. Otherwise it makes no claims at all to
tag the _last_ observation in each panel and in fact that it is not what
it does: it tags the first in the (current) sort order (although you
should not care, as they are the same). 

Nick 

fjc fjc

Check help egen tag

On Mon, Sep 8, 2008 at 7:05 AM, Diddy Antai <diddy.antai@ki.se> wrote:


>     Could you help me with the command that creates a new
> variable "newid" that is 1 for the last observation for each
> individual and missing otherwise.
>
> I have a dataset with multiple observations (mothers), and I want to
> create a variable with each mother appearing once irrespective of the
> number of children she has.

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