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st: RE: Re: Create dummy variable in panel


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Re: Create dummy variable in panel
Date   Sun, 4 Feb 2007 17:03:27 -0000

Just a matter of style, but to note first that this 
can be telescoped: 

bysort year : egen median_by_year = median(ta) 
gen large = ta > median_by_year 

However, a more serious point is that missings should usually be trapped: 

gen large = cond(missing(ta), ., (ta > median_by_year)) 

Nick 
n.j.cox@durham.ac.uk 

Zou Hong
 
> sort year
> by year: egen median_by_year=median(ta)
> gen large==0
> replace large=1  if ta>median_by_year

Christian Andres
 
> > I have a problem generating a dummy variable in a panel dataset.
> > 
> > My dataset contains 300 companies over 10 years. For each 
> company, I 
> > have a size measure, total assets (ta). What I want to do 
> now, is to 
> > generate a dummy variable which is 1 if the company's size 
> is larger 
> > than the sample median in each year. This means that I need ONE 
> > variable, say "large" which first lists this measure for 
> ten years for 
> > company 1, then 10 years for company 2...
> > 
> > To make things easier to understand:
> > In year 1996 the median is 50, in 1997 60, in 1998 55:
> > 
> > company year   ta    DUMMY_LARGE
> > 1       1996   51         1
> > 1       1997   53         0
> > 1       1998   56         1
> > 1....

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