st: how to identify unique id variables within groups?

[Jia Xiangping <jiajoseph@googlemail.com>]

Dear all,

For a datafile like :
id                    var1

1			1
1			2
1			3
2			1
2			2
2  		        1

I expect to check whether the value of "var1" within one group of "id"
is unique -- i.e. in group 2, the values are not unique. For a
non-grouped datafile, syntax like -isid- or -duplicates- is able to do
the work. But none of them works when combining with -by-.  Is there
any approach to check the unique  value within groups?

Thanks.



-- 
Xiangping Jia
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