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RE: st: on balancing a panel data


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: on balancing a panel data
Date   Mon, 13 Sep 2010 12:37:46 +0200

<>

The first two lines in Chris` code could be easily telescoped: 

***********
use http://www.stata-press.com/data/r11/nlswork.dta, clear
qui xtset
gen ones=1
bysort `r(panelvar)': egen numobs=sum(ones)

qui xtset
bysort `r(panelvar)': gen numobs2=_N

compare numobs numobs2
***********


HTH
Martin

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Chris Parker
Sent: Montag, 13. September 2010 11:59
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: on balancing a panel data

Sorry if this gets sent twice.  I wasn't sending text only before.

gen ones=1
bysort country: egen numobs=sum(ones)
su numobs, meanonly
drop if numobs<r(max)
drop ones numobs

Should do what you want.

Chris Parker

________________________________

PhD Candidate | Management Science & Operations
London Business School | Regent's Park | London NW1 4SA | United Kingdom
Direct line +44 (0)20 7000 8816 | Email cparker.phd2007@london.edu

On Mon, Sep 13, 2010 at 3:20 PM, <rado645-bg@yahoo.de> wrote:
>
> to avoid misunderstanding i need to correct a sentence in my post:please
read
> "i.e. to keep only those
>
> countries for which data is available for each year and exclude the rest"
as
> "i.e. to keep only those countries that appear each year and exclude the
rest".
>
> In the example I have given, this would be then countries 1 and 2.
>
>
>
> ----- Ursprüngliche Mail ----
> Von: "rado645-bg@yahoo.de" <rado645-bg@yahoo.de>
> An: statalist@hsphsun2.harvard.edu
> Gesendet: Montag, den 13. September 2010, 11:31:36 Uhr
> Betreff: st: on balancing a panel data
>
> Dear all,
>
> I have a panel data set of observations for countries over several years.
The
> number of countries varies: the minimum number  is 52 per year and the
maximum
> number is 73. For certain reasons (graphs),  I would like to make the
panel
> dataset a kind of balanced and I need to have the same countries in each
year
> across the sample period even if I would need to exclude some of them.
>
> Could you help me on how one can make this in Stata, i.e. to keep only
those
> countries for which data is available for each year and exclude the rest.
Below
> is a simplified description of the dataset:
>
> year      country    var1
> 1990     1              ...
> 1990      2             ...
> 1990      3
> 1991     1
> 1991     2
> 1992     1
> 1992     2
> 1992    3
> 1992    4
> 1992    5
> 1993    1
> 1993    2
> 1993    5
> ...
>
>
>
>
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>
>
>
>
> *
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>
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