How to remove repeating rows without unique function?

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Andrew Poissant 2017-9-25

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https://ww2.mathworks.cn/matlabcentral/answers/358267-how-to-remove-repeating-rows-without-unique-function

评论： Cedric 2017-9-26

I have a 624x2 matrix of ordered pairs, of which there are some repeating rows that I must remove. Is there a way to remove these repeating rows without using the unique function? Maybe using a for loop? The reason I can't use the unique function is because when I implement this matlab script in Simulink's Matlab Function block, the matrix must be sorted first before using the unique function. I can't sort the matrix because I will lose my ordered pairs and sortrows doesn't solve the issue either because I get the same error from Simulink.

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Cedric 2017-9-25

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编辑：Cedric 2017-9-25

在 MATLAB Online 中打开

Use the 'stable' option:

 >> A = randi( 3, 10, 2 )
 A =
   3
   1
   1
   1
   1
   3
   3
   1
   3
   1
 >> unique( A, 'rows' )
 ans =
   1
   1
   3
   1
   3
 >> unique( A, 'rows', 'stable' )
 ans =
   3
   1
   1
   3
   1

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Andrew Poissant 2017-9-26

It worked! Thank goodness. Really appreciate all of the help you gave me, you rock!

Cedric 2017-9-26

My pleasure. The amount of unsupported features seems to be a real pain, good luck with the rest!

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Jan 2017-9-26

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https://ww2.mathworks.cn/matlabcentral/answers/358267-how-to-remove-repeating-rows-without-unique-function#answer_283159

编辑：Jan 2017-9-26

在 MATLAB Online 中打开

I still do not understand, why you cannot simply sort the data. But this might be useful:

!!! UNTESTED !!!

function Data = UniqueRows2(Data)
nRow = size(Data, 1);
keep = true(nRow, 1);
for k1 = 1:nRow
  if keep(k1)
    for k2 = k1 + 1:nData
      if keep(k2)
        % For rows of length 2:
        keep(k2) = (Data(k2, 1) ~= Data(k1, 1)) | (Data(k2, 2) ~= Data(k1, 2));
        % General row length:
        % keep(k2) = any(bsxfun(@ne, Data(k2, :), Data(k1, :)), 2);
      end
    end
  end
end
Data = Data(keep, :);
end

This might be faster with vectorization:

function Data = UniqueRows(Data)
nRow = size(Data, 1);
keep = true(nRow, 1);
for k1 = 1:nRow
  if keep(k1)
    keep(k1 + 1:nData) = and(keep(k1 + 1:nData), ...
        any(bsxfun(@ne, Data(k2, :), Data(k1, :)), 2));
  end
end
Data = Data(keep, :);
end