Hi, I have two products which are substitudes. I try to fix a system as below to mydata. Demand1 = A1 -B1*Price1 + C1*Price2 Demand2 = A2 +B2*Price1 - C2*Price2 I would expect C1 & B2 to be symmetric, If they are truly substitude. How can I enforce this symmetry when creating a system of equations via SystemFit ? -- View this message in context: http://www.nabble.com/SystemFit-tp24588252p24588252.html Sent from the R help mailing list archive at Nabble.com.
Ferdogan wrote:> > Hi, > > I have two products which are substitudes. I try to fix a system as below > to mydata. > > Demand1 = A1 -B1*Price1 + C1*Price2 > Demand2 = A2 +B2*Price1 - C2*Price2 > > I would expect C1 & B2 to be symmetric, If they are truly substitude. How > can I enforce this symmetry when creating a system of equations via > SystemFit ? >-- View this message in context: http://www.nabble.com/SystemFit-tp24588252p24713807.html Sent from the R help mailing list archive at Nabble.com.
Hi Ferdogan, Sorry for the late response. On Thu, Jul 23, 2009 at 8:29 AM, Ferdogan<ferdogans at hotmail.com> wrote:> I have two products which are substitudes. I try to fix a system as below to > mydata. > > Demand1 = A1 -B1*Price1 + C1*Price2 > Demand2 = A2 +B2*Price1 - C2*Price2 > > I would expect C1 & B2 to be symmetric, If they are truly substitude. How > can I enforce this symmetry when creating a ?system of equations via > SystemFit ?Please take a look at http://www.jstatsoft.org/v23/i04/ I suggest that you estimate the system without the restriction first and then try to impose the restriction (and test it!). If you still do not manage to estimate the (restricted) system, please don't hesitate to send another email with a more precise/specific question to this mailing list. Best wishes, Arne -- Arne Henningsen http://www.arne-henningsen.name