黃河泉 发表于 2019-3-1 10:35 
你有看清楚我上面的指令吗?
两个命令分别是这样的
egen section = group(HS)
variable section already defined
r(110);
. xtset section year
repeated time values within panel
r(451);
. egen section = group(HS)
variable section already defined
r(110);
. duplicates list section year
Duplicates in terms of section year
+----------------------------------+
| group: obs: section year |
|----------------------------------|
| 1 1 1 2003 |
| 1 2 1 2003 |
| 1 3 1 2003 |
| 1 4 1 2003 |
| 1 5 1 2003 |
|----------------------------------|
| 1 6 1 2003 |
| 1 7 1 2003 |
| 1 8 1 2003 |
| 1 9 1 2003 |
| 1 10 1 2003 |
|----------------------------------|
| 1 11 1 2003 |
| 1 12 1 2003 |
| 1 13 1 2003 |
| 1 14 1 2003 |
| 1 15 1 2003 |
|----------------------------------|
--more--