search for: xtomegainv

...restrictions on the coefficients (i.e., that the â1 in all equations is the same value, and the same for all the other coefficients). When I try to run the model without the restricting equations (C2, C3) it runs just fine, but when I add these two equations I get the error: "Error in solve(xtOmegaInv %*% xMat2, xtOmegaInv %*% yVec, tol = solvetol) : cs_lu(A) failed: near-singular A (or out of memory)" Any ideas on what the problem might be? All the best, Rui Neiva P.S.: I've also posted this question on the Matrix help forum, but since I do not know how active that forum is I'...