Bookmark and Share

Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: reshaping data?

To, Nick Cox <>
Subject   Re: st: reshaping data?
Date   Thu, 25 Oct 2012 16:39:48 +0200

dear Nick,
thanks for your prompt reply. Unfortunately, the number of items is not fixed
best regards

Quoting Nick Cox <>:

This model formulation makes me feel a bit queasy, but I think what
you want is something like this.

Suppose for concreteness the number of items is fixed at 8. (I don't
see how this will work if the number is not fixed.) So, "for any value
of 8"

sort code_family code_item
forval i = 1/8 {
       by code_family : gen P`i' = P[`i']

Note that, contrary to your title, there is no -reshape- here as you
want your observations to remain observations; at least that's my


On Thu, Oct 25, 2012 at 3:08 PM,  <> wrote:

I have to estimate the equation


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

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?

*   For searches and help try:

This message was sent using IMP, the Internet Messaging Program.

**** 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 indicato (oppure alla persona responsabile di  rimetterlo al destinatario). Vogliate tener presente che qualsiasi uso, riproduzione o divulgazione di questo messaggio e' vietato. Nel caso in cui aveste ricevuto questo messaggio per errore, vogliate cortesemente avvertire il mittente e distruggere il presente  messaggio.

*   For searches and help try:

© Copyright 1996–2018 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   Site index