AW: st: RE: RE: estimation with a time trend.

["Martin Weiss" <martin.weiss1@gmx.de>]

<> 

You can just subtract the mean/median from your years to center the
variable:

*************
use http://www.stata-press.com/data/r11/nlswork.dta, clear
su year, d
gen centeredyear=year-r(p50)
su centeredyear year
*************



HTH
Martin

-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von natasha agarwal
Gesendet: Montag, 5. Juli 2010 13:38
An: statalist@hsphsun2.harvard.edu
Betreff: Re: st: RE: RE: estimation with a time trend.

On Mon, Jul 5, 2010 at 11:03 AM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> As -egen, group()- maps to 1 ... whatever regardless of gaps, this might
> in fact make things worse. What's wrong with -year- (or -year- MINUS
> midpoint) for interpretability?

I am afraid I did not understand "year- (or -year- MINUS> midpoint)
for interpretability?"

Thanks
Natasha

> Nick
> n.j.cox@durham.ac.uk
>
> Martin Weiss
>
> Your code maps years in your dataset to integer numbers, and I am not
> sure
> that it gets you any closer to your final destination. So far, it has
> not
> hurt either...
>
> natasha agarwal
>
> I was trying to estimate a production function with an unbalanced
> firm-year panel data and wanted to include a time trend. However I was
> not sure if the time trend was created correctly.
>
> egen t=group(year)
>
> I was wondering if anyone could please tell me if this was correct?
>
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