How to Find Column Duplicates

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RDG
RDG 2014-6-25
评论： Jos (10584) 2014-6-25
Suppose:
A{1}=
2 3 1 2
2 1 1 3
2 3 2 4
2 5 2 5
2 6 2 6
2 2 5 2
How can I find the duplicate value and their indices for column 3? Resultant should be: Value: 1,2 Indices: Can be 1,3 --OR-- 1,2,3,4,5.
I tried unique but it returns 5 as well, which is something I don't want.
Gracias.

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Jos (10584)
Jos (10584) 2014-6-25
X = A{1}
X = X(:,3) % just column 3
[a,i,j] = unique(X) % find all unique elements
n = histc(j,1:numel(a)) % frequency
tf = n > 1 % Which occur more than once?
required result = a(tf) % select those
  2 个评论
RDG
RDG 2014-6-25
Thanks for the prompt reply. What about the indices of those value? (2nd part of the question)

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