之前用center命令对变量做标准化处理，显示unrecognized command:  center；用foreach做一直显示foreach x of varlist stbrd a06 a01 age b01 b06 b07 b09 b08a b08b b11 b12 b13 b14a1 b14b1 b15a1 b15b1 b1900 b1901 b1902 b1903 b1904 a1201 a1> 202 a1203 a1204 a1205 a1206 a1207 a16 a17 a1801 a1802 a1803 a1804 a1805 b2301 b2302 b2303 b2304 b2305 b2306 b2307 b2308 b24a1 b24b1 b24a2 b
> 24b2 b24a3 b24b3 b24a4 b24b4 b24a5 b24b5 b2501 b2502 b1001 b1002 b30 b31 b32 b33 b34 b35 c22 c23 c24 c25 schloc_5c schtype_4c be1203 be1204
>  be1205 be30 be3103 be3105 be3106 stlb_2c stmigrant sthktype{
  2. egen x'1=std(x')
  3. }
' invalid name