Hello, Statalisters!
I have a simple question but got stuck on a simple solution. I have a panel
and let's say cross-section id is gvkey and time id is year. There are two
variables, say, primary sic and secondary sic. My aim to count the unique
value of sic in both variables by gvkey by year. I know the 'by' thing is
straightforward but is there a quick solution to count the unique
observation in both variables? I know the commands such as unique, distinct
and egenmore nvals. They work perfect for a single variable. Also, on the
webpage there is a explanation of the unique combination of two variables
and how to count that. I guess mine is different. Your help is appreciated.
Cheers,
Wanli Zhao
Using Stata 9
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