Re: [R] ols/gls or systemfit (OLS, WLS, SUR) give identical results

From: Spencer Graves <>
Date: Mon 17 Jul 2006 - 12:33:06 EST

          I can't say without more information. If the system were saturated (i.e., has as many equations as unknowns), you should get the same answer from all the different methods. However, I just tried a saturated model in 'systemfit', with the following results:

 > DF2 <- data.frame(y=1:2, x=3:4)
 > lm(y~x, DF2)
lm(formula = y ~ x, data = DF2)


(Intercept)            x
          -2            1

 > library(systemfit)
 > systemfit("OLS", list(eqn=y~x), data=DF2) Error in solve.default(sigma, tol = solvetol) :

        system is computationally singular: reciprocal condition number = 0  >

          If you'd like more help from this listserve, please supply a simple, self-contained example to illustrate your question (as suggested in the posting guide! "").

	  Hope this helps.
	  Spencer Graves

Mihai Nica wrote:
> I might be sorry for asking this question :-)
> I have two equations and I tried to estimate
them individually with "lm" and "gls", and then in a system (using systemfit) with "OLS", "WLS" and "SUR". Quite surprisingly (for myself at least) the results are identical to the last digit.
> Could someone (please!) give a hint as to what
am I doing wrong?
> Thanks,
> mihai
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> PLEASE do read the posting guide! mailing list PLEASE do read the posting guide! Received on Mon Jul 17 12:36:42 2006

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