-duplicates- doesn't need to work with -by:-.
You just need to include the variable(s) you would feed to -by:- in the varlist you feed directly to -duplicates-.
Thus
duplicates <whatever> id var1
is a template for working with duplicates in your sense. Here <whatever> is whatever subcommand you need.
The same comment applies to -isid-.
isid id var1
works out whether -id var1- jointly serve to identify observations uniquely.
Thus existing (official) commands suffice for your problem.
Nick
[email protected]
Jia Xiangping
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?
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
