[Limdep Nlogit List] hausmantest

[Caroline Johanna Biehl]

Dear all, 
The following hausman-test for my unbranded logit model leads to a negative difference matrix. Is there a way to change that?
Thank you very much, 
caroline

?Hausman test
sample; all$
reject; cset=-999$
nlogit
;lhs= choice, cset, alti
;choices= a, b, c, other
;show
; model: 
U(A) = Fre1*Fre1 + Fre2*fre2 + mo*mo + rest1*rest1+ rest2*rest2 + p*p  + p1*p1 + p2*p2  + inc*inc/
U(B) = Fre1*Fre1 + Fre2*fre2 + mo*mo + rest1*rest1+ rest2*rest2 + p*p + p1*p1 + p2*p2  + inc*inc/
U(C) = Fre1*Fre1 + Fre2*fre2 + mo*mo + rest1*rest1+ rest2*rest + p*p + p1*p1 + p2*p2  + inc*inc/
U(other)= 0$

matrix; j1=[1,0,0,0,0,0,0,0,0/
		0,1,0,0,0,0,0,0,0/
		0,0,1,0,0,0,0,0,0/
		0,0,0,1,0,0,0,0,0/
		0,0,0,0,1,0,0,0,0/
		0,0,0,0,0,1,0,0,0/
		0,0,0,0,0,0,1,0,0/
		0,0,0,0,0,0,0,1,0]$
matrix; bu=j1*B; Vu=J1*VARB*j1'$

reject; alti=1$
reject; cs1=1$
create; csetnew=3$
create; if(alti=2)altinew=1$
create; if(alti=3)altinew=2$
create; if(alti=4)altinew=3$

?Exclude a
nlogit
;lhs= choice, csetnew, altinew
;choices=  b, c, other
;show
; model: 
? U(A) = Fre1*Fre1 + Fre2*fre2 + mo*mo + rest1*rest1+ rest2*rest2 + p*p  + p1*p1 + p2*p2  + inc*inc/
U(B) = Fre1*Fre1 + Fre2*fre2 + mo*mo + rest1*rest1+ rest2*rest2 + p*p + p1*p1 + p2*p2  + inc*inc/
U(C) = Fre1*Fre1 + Fre2*fre2 + mo*mo + rest1*rest1+ rest2*rest + p*p + p1*p1 + p2*p2  + inc*inc/
U(other)= 0$

matrix; j2=[1,0,0,0,0,0,0,0,0/
		0,1,0,0,0,0,0,0,0/
		0,0,1,0,0,0,0,0,0/
		0,0,0,1,0,0,0,0,0/
		0,0,0,0,1,0,0,0,0/
		0,0,0,0,0,1,0,0,0/
		0,0,0,0,0,0,1,0,0/
		0,0,0,0,0,0,0,1,0]$
matrix; br=j2*B; Vr=J2*VARB*j2'$

matrix; bd=bu-br; vd=Vu-Vr$
matrix; vindv=[vd]$
matrix; list;q=bd'*vindv*bd$
CALC;list;p=1-chi(q,8)$

Output:
Matrix Q        has  1 rows and  1 columns.
               1
        +--------------
       1|   -8.69069
--> CALC;list;p=1-chi(q,8)$
  Error   471: Cannot compute CHI; parameter 1 is < = 0
  Error   116: CALC - Unable to compute result. Check earlier message.
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