用stata做面板数据的单位根检验，命令用hadrilm, 请问红颜色的结果是什么意思？怎么解决，谢谢


. tsset code year
       panel variable:  code (unbalanced)
        time variable:  year, 2006 to 2009, but with gaps
                delta:  1 unit
. hadrilm
varlist required
r(100);

. hadrilm  staff
Number of gaps in sample:  72
sample may not contain gaps
invalid syntax