is it possible to detect repeated values in a matrix?how?

For example I have a matrix such;

 A=[5  13  2  7  1 8; 2  4  5  7  8  23 31;5  65  34  12  31  8]

which has a size (nx6)

If we look through first column, first and third row values are same. I just want to detect the repeated values in the 1st column in all rows. How can I do that?

Thanks

Answer 1

[AJ von Alt]

This can be done using hist and unqiue. See How can I count the occurrences of each element in a vector in MATLAB? for more information.

   A=[5  13  2  7  1 8; 2  4  5  7  8  23;5  65  34  12  31  8];

   % Find the unique values
   uniqueVals = unique( A(:,1) );

   % Count the number of instances of each of the unique vals
   valCount = hist( A(:,1) , uniqueVals )';

Answer 2

[Matt J]

length(unique(A(:,1)))<size(A,1)

[husot]

thanks but when I use that I find how many rows are repeated. I want to detect which rows are repeated.

[Matt J]

How about

 [U,I]=unique(A(:,1));

 repeated = setdiff(1:size(A,1),  I),

For your example, this returns 3 because row 3 is a repetition of row 1. If this isn't what you want, see the documentation for UNIQUE. It gives you lots of different options for analyzing repetition.

[husot]

I made it, thanks!