Re: st: re: constraints

[Richard Williams <Richard.A.Williams.5@ND.edu>]

At 06:45 PM 6/28/2005 -0400, Kit Baum wrote:
> Although cnsreg is useful, it is hardly necessary for Vidya's problem:
>
> "I am trying to estimate an equation similar to this -
>
> constraint define 1 L.wpi+L2.wpi+L3.wpi=1
> cnsreg wpi L.wpi L2.wpi L3.wpi L.ygapm L2.ygapm sswpi L.sswpi, constraint(1)"
>
> This constraint may be rewritten as b(L3) = 1-b(L)-b(L2)  and merely 
> substituted into the equation,
>
> (wpi - L.wpi)   regressed on (L.wpi-L3.wpi),  (L2.wpi-L3.wpi) and the rest
>
> which you can estimate with regress, robust.
>
> If you want the coefficient on L3.wpi, calculate it via lincom.
>
> Kit
Since I made the claim that many/most/all problems involving (linear) 
constraints could be handled by regular regression as well as by cnsreg, I 
am glad Kit was able to do the algebra on this one!  However, does this 
produce a correct R^2, which is what Vidya was seeking in the first 
place?  I was thinking of situations where all the manipulations could be 
done on the RHS, but here the LHS has to be changed.


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Richard Williams, Notre Dame Dept of Sociology
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