Not sure about OP's real intention, but this is the quote from the initial post, maybe the course has been shifted down the line? "I'm wanting to delete all pairs (i.e both entires) leaving me with only the observations which only appear once i.e were not one of a pair." You are right, it will remove both, because that is exactly what OP desires, or at least appeared to be so, judging from the above statement. Well, at the same time, I agree this may NOT be a case that is 'beyond reasonable doubt", per se . Haikuo
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