st: Create a flag variable for 10 most frequent values

["Cohen, Elan" <cohened@upmc.edu>]

Hi all,

I have a string variable dx that represents a patient's diagnosis (about 5,000 unique values).  I'd like to create a "top 10 flag" that equals 1 if dx is one of the top 10 most frequent diagnoses and 0 otherwise.  

I'm not even sure where to begin.  If someone could point me in the right direction, I'd be grateful.  Stata 10, Windows XP

Thank you,

- Elan

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