生成经济权重举证时出现：有一行元素都为0，不能标准化，是什么情况？
. spwmatrix gecon latitude longitude, wn(wfj) wt(econ) econvar( avegdp ) noisla
> nd rowstand

N.B.: Elements of one row of the weights matrix sum up to zero; weights matrix
> was not row-standardized

This row is:
  14
You might want to rethink your weights structure criteria.
An alternative is to specify the noisland option to generate the spatial weight
> s without the island observation:

Economic distance spatial weights matrix (30 x 30) calculated successfully and
> the following action(s) taken:

- Spatial weights matrix  created as Stata object(s): wfj.