Re: st: Fixing the value in egen command

[Michael Hanson <mshanson@mac.com>]

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/
> > -----------------------------------------
> >
> >
> >
> > *
> > *   For searches and help try:
> > *   http://www.stata.com/help.cgi?search
> > *   http://www.stata.com/support/statalist/faq
> > *   http://www.ats.ucla.edu/stat/stata/
>
>
> --
> 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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> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/

*
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