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RE: st: RE: How to construct a duration variable?


From   "Alex Ogan" <aogan@ArrowstreetCapital.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: How to construct a duration variable?
Date   Thu, 6 Apr 2006 16:39:12 -0400

Here's one in two lines:

bysort hhid (period): gen tempvar = sum(switch)
bysort hhid tempvar: gen myduration = _N


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Winter
Sent: Thursday, April 06, 2006 4:14 PM
To: statalist@hsphsun2.harvard.edu
Subject: RE: st: RE: How to construct a duration variable?

Good point.  Drat.



At 04:05 PM 4/6/2006, you wrote:
>Not so. Each person can have one or more
>spells on each -Brand-. Your code lumps
>them all together.
>
>Nick
>n.j.cox@durham.ac.uk
>
>Nick Winter
>
> > I think
> >
> >    bysort hhid Brand: gen Duration=_N
> >
> > should do it.
> >
> > --Nick Winter
> >
> > At 01:42 PM 4/6/2006, you wrote:
> > >Thank you, Nick.
> > >
> > >For example,  there are three brands in the market: A, B and C.
One
> > >consumer buy A at the first period.  At the second period, she
> > >switches to B.  Since then, she keeps buying B for the next four
> > >periods.  After that, she switches to C etc.
> > >
> > >Then the duration variable I want should be:
> > >
> > >hhid    Period   Brand    Switch  Duration
> > >1         1         A           0           1
> > >1         2         B           1           4
> > >1         3         B           0           4
> > >1         4         B           0           4
> > >1         5         B           0           4
> > >1         6         C           1           2
> > >1         7         C           0           2
> > >1         8         A           1           1
> > >1         9         B           1           4
> > >1        10         B           0           4
> > >1        11         B           0           4
> > >1        12         B           0           4
> > >1        13         C           1           2
> > >1        14         C           0           2
> > >
> > >I wish that it's clear this time.  I just not sure how to construct
> > >the duration variable in Stata.
>
>
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________________________________________________________
Nicholas J. G. Winter                     607.255.8819 t
Assistant Professor                       607.255.4530 f
Department of Government              nw53@cornell.edu e
Cornell University        falcon.arts.cornell.edu/nw53 w
308 White Hall
Ithaca, NY 14853-4601 


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