Set same elements in a matrix to zero

Question

WEN SHIN LU 2022-4-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1704555-set-same-elements-in-a-matrix-to-zero

回答： Matt J 2022-4-25

采纳的回答： Matt J

Hi,

I have a large matrix which has duplicate elements in neighborhood.

For example,

A = [0 0 0 01 1 0 0 0 2 2 2 0 0 0 5 5 5 5 5;

0 0 0 1 1 0 0 0 0 0 2 2 0 0 0 5 0 5 0 5;

0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 5 0 5 0]

I have to keep just a unique element in an arbitrary position. Could I use loop to solve this problem?

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Jan 2022-4-25

What is the wanted output for this example?

WEN SHIN LU 2022-4-25

sorry didn't explain clearly. The output can be:

A = [0 0 0 01 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0;

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 0 0 0 0;

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]

I want to keep just one repeated element in its neighborhood.

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Answer 1

Matt J 2022-4-25

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https://ww2.mathworks.cn/matlabcentral/answers/1704555-set-same-elements-in-a-matrix-to-zero#answer_950465

在 MATLAB Online 中打开

Without the Image Processing Toolbox,

A = [0 0 0 0 1 1 0 0 0 2 2 2 0 0 0 5 5 5 5 5;
       0 0 0 1 1 0 0 0 0 0 2 2 0 0 0 5 0 5 0 5;
       0 0 0 0 1 0 0  0 0 0 0 0 0 0 0 0 5 0 5 0]
A = 3×20
     0     0     0     0     1     1     0     0     0     2     2     2     0     0     0     5     5     5     5     5
     0     0     0     1     1     0     0     0     0     0     2     2     0     0     0     5     0     5     0     5
     0     0     0     0     1     0     0     0     0     0     0     0     0     0     0     0     5     0     5     0
[I,J,S]=find(A);
IJS=num2cell(splitapply(@(x) x(1,:), [I,J,S],findgroups(S)),1);
[I,J,S]=deal(IJS{:});
B=accumarray([I,J],S,size(A))
B = 3×20
     0     0     0     0     0     0     0     0     0     2     0     0     0     0     0     5     0     0     0     0
     0     0     0     1     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0

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Answer 2

Matt J 2022-4-25

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1704555-set-same-elements-in-a-matrix-to-zero#answer_950430

编辑：Matt J 2022-4-25

在 MATLAB Online 中打开

Something like this, perhaps?

A = [0 0 0 0 1 1 0 0 0 2 2 2 0 0 0 5 5 5 5 5;
       0 0 0 1 1 0 0 0 0 0 2 2 0 0 0 5 0 5 0 5;
       0 0 0 0 1 0 0  0 0 0 0 0 0 0 0 0 5 0 5 0]
A = 3×20
     0     0     0     0     1     1     0     0     0     2     2     2     0     0     0     5     5     5     5     5
     0     0     0     1     1     0     0     0     0     0     2     2     0     0     0     5     0     5     0     5
     0     0     0     0     1     0     0     0     0     0     0     0     0     0     0     0     5     0     5     0
reg=regionprops(A~=0,'PixelIdxList');
B=zeros(size(A));
for i=1:numel(reg), 
   
    j=reg(i).PixelIdxList(1);
    B(j)=A(j);
end
B
B = 3×20
     0     0     0     0     0     0     0     0     0     2     0     0     0     0     0     5     0     0     0     0
     0     0     0     1     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0