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Re: st: merge creates duplicates in master data

From   Will Hauser <>
Subject   Re: st: merge creates duplicates in master data
Date   Mon, 26 Apr 2010 09:20:59 -0400

I appreciate your help but could you be a bit more clear about the joinby command? Joinby results in many more duplicates than I obtain with the merge command. The unmatched option must be specified as none (the default), master, using, or both. I tried 'none' and 'master', the two plausible specifications but both result in several hundred duplicates.

My primary concern with the merge command is not so much the resulting duplicates - they are few and I can identify and remove them with the 'duplicates' command. Rather, it is that I do not fully understand the command itself or there is some flawed logic in my multi-step approach. Additional documentation on the merge command or any other insights as to how I might best match these lists would be most helpful.

One tidbit I did not add in the first post is that in addition to the update option I am also using the nokeep option. The master list is the definitive list if an observation is not on that list then that observation will not be needed.

I may try to track down a copy of stata11 to try the new merge command. Thanks for that suggestion.


Jose Ricardo Nogueira wrote:
Stata 11 has a new merge command that will get rid of this problem,
but in Stata 10 you can do this with joinby command and unmatched



Hello all,

I am experiencing unexpected behavior in Stata 10 when using the merge
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