st: checking for repeated values of a given variable

[Kenley Barrett <k-barrett@northwestern.edu>]

I'm creating an ID variable to uniquely identify each case in a dataset 
that I'm piecing together, and it appears that here and there there are 
mistakes in the dataset that result in identical values of the ID variable 
for different cases. The dataset is way too big to look through all of it; 
is there a command that will check to make sure that no values are repeated 
for a given variable?

Thanks,
Kenley

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