我的非平衡面板数据，我用了插值法进行处理，每个变量都处理了，然后把以前的变量删除了。但在做单位根检验的时候，仍然还是显示我的数据是非平衡数据，还是无法进行单位根检验。
帮帮忙吧，我都急死了，查了一天的资料，也没个头绪，这个论坛难道没人遇到过这个问题吗？
. by i: ipolate lntotdebt year, gen(ilntotdebt) epolate
(18792 missing values generated)
. by i: ipolate lnprofit year, gen(ilnprofit) epolate
(240472 missing values generated)
by i: ipolate lnasset year, gen(ilnasset) epolate
(16831 missing values generated)
. by i: ipolate lnfinafee year, gen(ilnfinafee) epolate
(289860 missing values generated)
. by i: ipolate lnsale year, gen(ilnsale) epolate
(19029 missing values generated)
. edit
- preserve
- drop lntotdebt
- drop lnprofit
- drop lnasset
- drop lnfinafee
- drop lnsale
. tsset i year
       panel variable:  i (unbalanced)
        time variable:  year, 2000 to 2007, but with gaps
                delta:  1 unit
. levinlin ilntotdebt, lag(1)
Levin-Lin-Chu test for ilntotdebt Deterministics chosen: constant
Number of gaps in sample:  28595
sample may not contain gaps
invalid syntax
r(198);