Checking Duplications

[Carmen Anthony Esposito]

I am trying to use xtset and I know how to remove any duplications. Is there a way to see if the non-id/time variables also repeat in value? For example, if I have

id	year	X
1	1	4
1	1	4

Could I see if X repeats along with those same observation id and year?

[Clyde Schechter]

by id year (X), sort: gen byte changing_x = (x[1] != x[_N])
browse if changing_x

will show you any id-year combinations where the value of x is not a constant within that group.