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find the repetition of matrix rows

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yousef Yousef
yousef Yousef on 7 May 2014
Edited: Image Analyst on 9 May 2014
I want to find out if the row i of mxn matrix is repeated ,the code should give logic 1.Otherwise zero"there are many ways but Im searching for the best one" Thanks
  2 Comments
José-Luis
José-Luis on 7 May 2014
And please instead of asking an almost repeated question, try to explain better what you want, and please show some effort before asking for a ready-made answer.

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Accepted Answer

Roberto
Roberto on 9 May 2014
Edited: Roberto on 9 May 2014
a = [1 2 3; 4 5 6;1 2 3; 3 2 4; 1 2 3; 3 2 1; 1 3 2] ;
row2check = 1;
repeated = 0 ;
for i = 1 : size(a,1)
repeated = repeated + prod(double([a(row2check,:)== a(i,:)])) ;
end
fprintf('\n Row number %i is reapeated %i times in matrix!\n\n',row2check,repeated);

More Answers (1)

Image Analyst
Image Analyst on 9 May 2014
Edited: Image Analyst on 9 May 2014
Using ismember() is the usual method. Try this:
m = randi(9, [5000, 3]); % Create sample data.
% For demo, let's make sure row 9 is a repeat.
% In other words, row 9 is a duplicate of row 1.
m(9,:) = m(1,:);
% Let's see if row i is repeated
i = 1; % Could be any number up to size(m, 1);
% Use ismember to find repeated rows.
[lia, locb] = ismember(m, m(i,:), 'rows');
% locb is a logival vector. Find the actual row numbers.
repeatedRows = find(locb)

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