Hoping someone here can help me with this small problem.
set.seed(2013)

x<-sort(c(letters,letters[sample(26,10,1)]))

This gives a vector of 36 letters with some muliples (in this case, g,m,s,t,u,v,x,y). Now what I need is to get rid of the ones that only occur once and keep the multiples. I need the opposite of the unique() function. I expect this should be pretty easy but I can't see it. Anyone know a solution? Thanks in advance!


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Kevin Parent, Ph.D
Korea Maritime University
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