用stata xtptm 命令做面板数据门槛回归时，出现r(3301)错误是哪里出错了，各位大神急求啊！！

. xtptm cs ztp hy zy ,rx(ty) thrvar(tq)
                 <istmt>:  3301  subscript invalid
r(3301);
error . . . . . . . . . . . . . . . . . . . . . . . . Return code 3301
        subscript invalid
        The subscript is out of range (refers to a row or column that
        does not exist) or contains the wrong number of elements.