我的stata12在升级前还好，升级后运行xtthres命令出现如下错误：
tsset code year
       panel variable:  code (strongly balanced)
        time variable:  year, 1978 to 2010
                delta:  1 unit
. xtthres dlcr ktl,thres(year) d(soeshare)
Begin Time :31 Dec 2012 14:24:07
You must tsset your data before using xtthres,see help xtthres.
. version 10
. xtthres dlcr ktl,thres(year) d(soeshare)
Begin Time :31 Dec 2012 14:24:16
You must tsset your data before using xtthres,see help xtthres.
声明版本后也不行，请问怎么办？