% Wald test for spatial Durbin model against spatial lag model
btemp=results.parm;
varcov=results.cov;
Rafg=zeros(K,2*K+2);
for k=1:K
Rafg(k,K+k)=1; % R(1,3)=0 and R(2,4)=0;
end
Wald_spatial_lag=(Rafg*btemp)'*inv(Rafg*varcov*Rafg')*Rafg*btemp
prob_spatial_lag=1-chis_cdf (Wald_spatial_lag, K)