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RE: st: Constraining alpha and theta in slogit


From   "Jun Xu" <mystata@hotmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: Constraining alpha and theta in slogit
Date   Mon, 14 Nov 2005 19:57:31 -0600

Dear Mike,

For setting the first constraint, it's like

constrain def 1 [phi1_1]_cons+[phi1_2]_cons+[phi1_3]_cons+...+[phi1_j]_cons=0

and it should work well, but I do find problems with your magnitude constraints. I only have limited working knowledge with slogit, so others or Stata staff might have some suggestions. But I guess one possibility why this does not work is probably slogit in Stata has used the first strategy (impose the first phi to be 1 and last to be zero) that DiPrete's paper mentioned just above the discussion on Goodman's strategy (P.761), and that might cause Goodman's strategy hard to implement?

P.S.: we are always proud of our distinguished member!

Jun Xu
Ph.D. Candidate
Department of Sociology
Indiana University at Bloomington






From: Michael Hout <mikehout@berkeley.edu>
Reply-To: statalist@hsphsun2.harvard.edu
To: statalist@hsphsun2.harvard.edu
Subject: RE: st: Constraining alpha and theta in slogit
Date: Mon, 14 Nov 2005 15:54:54 -0800

Dear Jun,
How about the constraint the DiPrete (1990) uses:
Sum_j phi_j = 0
Sum_j phi_j^2 = 1

I have not been able to figure that out.
-Mike
PS Warm greetings to my friends and your mentors in Bloomington!
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