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Re: st: Selecting within a subset of observations


From   Maarten Buis <maartenlbuis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Selecting within a subset of observations
Date   Thu, 13 Jun 2013 11:16:59 +0200

On Thu, Jun 13, 2013 at 10:52 AM, Ada Keding wrote:
> I am trying to use min/max or similar within a subset of observations.
>
> For example, I have one or more event dates for different identifiers:
<snip>
> Now I would like to create a variable that displays the latest event
> date within each identifier.

Here is how I would do this:

*------------------ begin example ------------------
// copy your example dataset
clear
input ID    str10 EventDate
1      "01/03/2011"
2      "31/01/2011"
2      "05/09/2011"
3      "12/03/2011"
end

// transform the datestring to Stata dates
gen date = date(EventDate,"DMY")
format date %td

// find the most recent event per ID
bys ID : egen last = max(date)

// format it, so it also looks like a date
format last %td

// admire the results
list
*------------------- end example -------------------
* (For more on examples I sent to the Statalist see:
* http://www.maartenbuis.nl/example_faq )

Hope this helps,
Maarten


---------------------------------
Maarten L. Buis
WZB
Reichpietschufer 50
10785 Berlin
Germany

http://www.maartenbuis.nl
---------------------------------
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