# Re: st: Fixing the value in egen command

 From Michael Hanson 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

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

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```
```
*
*   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/
```