Find repeated values in a matrix

How can I find repeated values at the same time in two columns of an array (12x2):

A = [26	24
    28	35
    31	34
    33	31
    33	31
    33	28
    35	25
    31	26
    30	26
    28	29
    27	30
    26	32];

In A the [33 31] is repeated. I tried to use the unique function but it only finds the unique values in a column.

[C, ia, ic] = unique(A(:,1), 'rows');

Thanks in advance.

Answer 1

[Walter Roberson]

A = [26	24
    28	35
    31	34
    33	31
    33	31
    33	28
    35	25
    31	26
    30	26
    28	29
    27	30
    26	32];
[C, ~, G] = unique(A, 'rows');
counts = accumarray(G, 1);
mask = counts > 1;
[counts(mask), C(mask,:)]

ans = 1×3

2 33 31

●

[Yro]

Thanks a lot, it works. One more question, if I want to know if some value is repeated or not?

[Walter Roberson]

[wasfound, idx] = ismember(ThingToFind, A, 'rows');
repcounts = zeros(size(wasfound));
repcounts(wasfound) = counts(idx(wasfound));

[repcounts, ThingToFind]

Here, ThingToFind may be a 2D array with the same number of columns as A has, and the associated count will be calculated for each entry.