How to Find Column Duplicates

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.

Answer 1

[Jos (10584)]

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

[RDG]

Thanks for the prompt reply. What about the indices of those value? (2nd part of the question)

[Jos (10584)]

requiredindices = i(tf)