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Re: st: Fixing the value in egen command


From   Michael Hanson <mshanson@mac.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Fixing the value in egen command
Date   Tue, 23 Dec 2008 09:55:52 -0500

That's because you did not follow Maarten's instructions.  Compare:

You:     bys country (year): gen initgdp = gdp[_n==1980]
Maarten: bys country (year): gen initgdp = gdp[_n==1]

_n is a counter, not your year variable. You want the first (_n=1) observation, not the one-thousand, nine hundred and eightieth (_n=1980) -- the latter doesn't even exist in your dataset. Stata sees _n and "year" as distinct variables. Only you know that 1980 (year==1980) is the first observation within each country (_n=1). Stata can index observations by its internal counter (_n), but not your year variable values.

Hope this helps,
Mike

On Dec 23, 2008, at 9:32 AM, Choudry T Shehzad wrote:

Thanks Martin:

But it changes all values to zero.

My data in very simple form is like

            country........year...GDP...initgdp*
            Argentina... 1980...300.....300
            Argentina... 1981...310....300
            Argentina... 1982...340....300
            Argentina... 1983...380....300

            Brazil......... 1980...400....400
            Brazil...........1981...410....400
            Brazil...........1982...440....400
            Brazil........... 1983..480....400


* The variable I want to make

When I use your command

bys country (year): gen initgdp = gdp[_n==1980]
bys country (year): replace initgdp = sum(initgdp)

all values of initgdp become zeros

May be I could not explain better earlier.

Best regards,

Tanveer


Maarten buis wrote:
--- Choudry T Shehzad <C.T.Shehzad@rug.nl> wrote:

Now I want to make another variable that contains initial value of
GDP fixed (for all years) equal to e.g. value of GDP in year 1885
corresponding to each country.


bys country (year): gen initgdp = gdp[_n==1]
bys country (year): replace initgdp = sum(initgdp)

Hope this helps,
Maarten


-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room N515

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------



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--
Choudhry Tanveer Shehzad (Tanveer)
PhD Student
Department of Finance,
Faculty of Economics & Business,
University of Groningen,
Nettelbosje 2
9747 AE Groningen
The Netherlands
Mobile: 0031-644801970
Home Page: http://www.rug.nl/staff/c.t.shehzad/

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