Re: st: reshaping data?

[agostino@unical.it]

thank you, of course I'm aware of the misspecification: it was just a  
simplified version of my actual regression, to illustrate may data  
problem!


Quoting Yuval Arbel <yuval.arbel@gmail.com>:

> Here is a link to an excellent book in consumer's behavior theory:
>
> http://www.amazon.com/Economics-Consumer-Behavior-Angus-Deaton/dp/0521296765
>
>
> On Thu, Oct 25, 2012 at 4:19 PM, Yuval Arbel <yuval.arbel@gmail.com> wrote:
> > Before going any further, please note that the model you proposed is
> > incorrectly specified. Any decent Econometric textbook will
> > demonstrate the endogeneity between P1 and Q1. Moreover, if you would
> > like to estimate the demand for each product - you need to have some
> > measure to the level of income of each consumer
> >
> > On Thu, Oct 25, 2012 at 4:08 PM,  <agostino@unical.it> wrote:
> > > Dear all,
> > > I would be grateful if you could help me to address the following problem:
> > > I have to estimate the equation
> > >
> > > Q1=a+b1P1+b2P2+...bnPn+e
> > >
> > > Where Q1 is the quantity of item 1 sold by a supermarket during a week , P1
> > > is the price of item 1 in that week, the other prices are those of the n
> > > items belonging to the same family of items. My data set is organized as
> > > follows:
> > >
> > >
> > > Code_item       week    Q       P       Code_family
> > > 789             1       8       2       1
> > > 790             1       25      4       1
> > > 791             1       9       1.3     1
> > >
> > > 792             1       12      2       1
> > >
> > > 800             1       7       2       2
> > > 801             1       20      1.2     2
> > > 802             1       11      1.6     2
> > >
> > > 803             1       12      2       2
> > >
> > > And so forth for the other weeks and families...
> > >
> > > For each item, how can I include in my regression the prices of the other
> > > (n-1) items of the same family, ignoring the prices of the items belonging
> > > to other families?
> > > Thank you in advance
> > > Maria
> > >
> > >
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> > >
> > >
> > >
> > >
> > > **** Riservatezza / Confidentiality ****
> > > In ottemperanza al D.Lgs. n. 196 del 30/6/2003 in materia di protezione dei
> > > dati personali, le informazioni contenute in questo messaggio sono
> > > strettamente riservate ed esclusivamente indirizzate al destinatario
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> > >
> > > *
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> >
> >
> >
> > --
> > Dr. Yuval Arbel
> > School of Business
> > Carmel Academic Center
> > 4 Shaar Palmer Street,
> > Haifa 33031, Israel
> > e-mail1: yuval.arbel@carmel.ac.il
> > e-mail2: yuval.arbel@gmail.com
>
>
>
> --
> Dr. Yuval Arbel
> School of Business
> Carmel Academic Center
> 4 Shaar Palmer Street,
> Haifa 33031, Israel
> e-mail1: yuval.arbel@carmel.ac.il
> e-mail2: yuval.arbel@gmail.com
>
> *
> *   For searches and help try:
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> *   http://www.ats.ucla.edu/stat/stata/



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**** Riservatezza / Confidentiality ****
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