* input the data
clear
input id year
1 1990
1 1990
1 1991
2 1990
2 1991
2 1991
end
* xtset , but stata report error!
xtset id year
repeated time values within panel
r(451);
* because, there are repeated year obs
duplicates report
Duplicates in terms of id year
--------------------------------------
copies | observations surplus
----------+---------------------------
1 | 2 0
2 | 4 2
--------------------------------------
* solution: drop duplicates
duplicates drop id year, force
Duplicates in terms of id year
(2 observations deleted)
* Now,xtset is OK
xtset id year
panel variable: id (strongly balanced)
time variable: year, 1990 to 1991
*-----Appdex--------The do files----------------
clear
input id year
1 1990
1 1990
1 1991
2 1990
2 1991
2 1991
end
cap xtset id year
duplicates report id year
duplicates drop id year, force
xtset id year