什么错误信息啊

. constraint 12 [lf]L.f=1

.
. sspace (f L.f L.lf, state noconstant)
variable lf not found
r(111);

.
. (lf L.f, state noconstant noerror)
unrecognized command:  ( invalid command name
r(199);

.
. (D.ipman f, noconstant)
unrecognized command:  ( invalid command name
r(199);

.
. (D.income f, noconstant)
unrecognized command:  ( invalid command name
r(199);

.
. (D.hours f, noconstant)
unrecognized command:  ( invalid command name
r(199);

.
. (D.unemp f, noconstant),
unrecognized command:  ( invalid command name
r(199);

.
. covstate(identity) constraints(12)
unrecognized command:  covstate
r(199);

那个命令应该写在一行上面，而不是分行写

谢谢！万分感谢！一语中的！

直接通过stata公司服务器下载例子的数据要注意容易产生数据丢失变量的问题……