Xtset Stata. The usual format is. Technical note In previous versions of Stata there was no xtset command.
But for the within s we only want variation within units and we want to ignore variation between units. 32 declare panel data structure. Xit x i x.
The xtset command tells Stata that these are Panel data.
The panel variable is country in this case - all observations for Sweden are connected all observations for Norway are connected and so. Xtreg health retired re time-constant explanatory variable. You need to do this before you can use the other xt commands. First we could calculate the within variance using Statas approach.
