MATLAB: Removing duplicate rows (not “unique”)

fast codematrix manipulation

I have a matrix with many (1e5+) rows and I want to remove both copies of all duplicate rows. Is there a fast way to do this? (This function needs to be run many times.)

Best Answer

Let A be your matrix.
   [B,ix] = sortrows(A);
   f = find(diff([false;all(diff(B,1,1)==0,2);false])~=0);
   s = ones(length(f)/2,1);
   f1 = f(1:2:end-1); f2 = f(2:2:end);
   t = cumsum(accumarray([f1;f2+1],[s;-s],[size(B,1)+1,1]));
   A(ix(t(1:end-1)>0),:) = []; % <-- Corrected
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