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


From   Nick Winter <nw53@cornell.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: How to construct a duration variable?
Date   Thu, 06 Apr 2006 13:50:13 -0400

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.

Thanks,

Albet





On 4/6/06, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> I think you are going to need to explain how "Duration"
> is calculated. The numerical example is not
> clear to me.
>
> Nick
> n.j.cox@durham.ac.uk
>
> Albert Newton
>
> >        I get stuck in coding a during variable.  The data is like:
> >
> > hhid    weekshoppingday triptype        switch  switchtype
> >   Duration
> > 1871877 954     7       1       0       0       0
> > 1871877 955     7       2       1       2       1
> > 1871877 956     3       1       1       4       1
> > 1871877 957     6       0       1       1       1
> > 1871877 958     7       1       1       6       3
> > 1871877 959     7       1       0       0       0
> > 1871877 960     7       1       0       0       0
> > 1871877 961     7       0       1       1       1
> > 1871877 962     7       2       1       5       1
> > 1871877 963     4       1       1       4       3
> > 1871877 964     2       1       0       0       0
> > 1871877 964     7       1       0       0       0
> >
> > I just wanto count how long the customer stay in the switched shopping
> > type.  Could any one give some suggestion of how to constuct the
> > variable "Duration"?
> > The one above is make manually.
>
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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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