[R-sig-Geo] Error in spdep: system is computationally singular (lagsarlm)

[Paolo Veneri]

I am trying to estimate a SAR model with the lagsarlm function:

SAR3nn <- lagsarlm(formula=formula(mod1),listw=list3nn.listw,type="lag",
method="eigen", data=d)

but I saw this message:

Error in solve.default(inf, tol = tol.solve) :
  system is computationally singular: reciprocal condition number =
5.74163e-27

It happens with both a k-nearest-neighbors matrix and with a distance matrix.
If I opt for a spatial 2sls model, the result is the same. I must say that
in the formula I have a variable and its square, which are very highly
correlated (about 0.9). The IV model works if I drop the squared variable,
while the lagsarlm still tells me that the system is singular.

Does anybody can help me? Thank you so much!

Paolo


-- 
Paolo Veneri
Dipartimento di Scienze Economiche e Sociali (DiSES)
Università Politecnica delle Marche
Piazza Martelli, 8 - 60121 Ancona (Italy)
Tel. +39 3392672827