stata运行命令：

. spwmatrix gecon latitude longitude, wname(wecon) wtype(econ) econvar(manugrp) rowstand xport(wecon,txt)

Economic distance spatial weights matrix (285 x 285) calculated successfully and the following action(s) taken:


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


- Spatial weights matrix has been row-standardized.


- Spatial weights matrix saved to .txt file, F:\Stata12/wecon.txt, for use with other Stata packages.

这时应该已经生成了权重矩阵wecon，可是再运行下面命令却提示：
. spmat import wedg using wecon.txt
. spmat save wecon using wecon.spmat   
spmat object wecon not found
r(498);

请各位大神看看到底哪里出错了？谢谢！