用stata做空间计量时的问题

想问一下如果做空间计量模型，权重矩阵不是对称的能够做出来吗？

以及在回归的过程中出现这类问题应如何解决呢？因为我选择的是地级市的数据，且删除了部分数据不完全的市区，会导致无法回归吗？
xsmle gdp k labor1,emat(W)model(sem)robust nolog noeffect
> s
numerical derivatives are approximate
nearby values are missing
numerical derivatives are approximate
nearby values are missing
numerical derivatives are approximate
flat or discontinuous region encountered
numerical derivatives are approximate
nearby values are missing
numerical derivatives are approximate
nearby values are missing
could not calculate numerical derivatives -- discontinuous
region with missing values encountered
could not calculate numerical derivatives -- discontinuous
region with missing values encountered

十分感谢！