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Re: st: re: constraints
At 06:45 PM 6/28/2005 -0400, Kit Baum wrote:
Although cnsreg is useful, it is hardly necessary for Vidya's problem:
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.
"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.
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
WWW (personal): http://www.nd.edu/~rwilliam
WWW (department): http://www.nd.edu/~soc
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