Populate matrix with non-zero elements from previous matrix

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Tomás Nunes 2018-4-13

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评论： Stephen23 2018-4-13

I have a 7567*32 matrix in which every row has 4 non-zero elements and the rest are zeros. I want to create a 7567*4 matrix that is populated only with the non-zero elements from the previous matrix. Is there a way to do so?

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Answer 1

Stephen23 2018-4-13

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编辑：Stephen23 2018-4-13

在 MATLAB Online 中打开

I guess you want to keep those non-zero values in the same rows in which case try this, where M is your matrix:

Z = M.';
Z = reshape(Z(Z~=0),4,7567).'

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Stephen23 2018-4-13

编辑：Stephen23 2018-4-13

在 MATLAB Online 中打开

Generate the indices from the first matrix, and get the values from the second matrix:

>> X = [0 1 -1 1 0 -1; -1 1 0 0 -1 1; 0 0 1 1 -1 -1]
X =
   0   1  -1   1   0  -1
  -1   1   0   0  -1   1
   0   0   1   1  -1  -1
>> M = [0 0.2 -0.3 0.4 0 -0.5; -0.6 1.3 0 0 0.1 1.5; 0 0 0.9 0.8 -0.1 -0.2]
M =
   0.00000   0.20000  -0.30000   0.40000   0.00000  -0.50000
  -0.60000   1.30000   0.00000   0.00000   0.10000   1.50000
   0.00000   0.00000   0.90000   0.80000  -0.10000  -0.20000
>> Z = M.';
>> Z = reshape(Z(0~=X.'),4,[]).'
Z =
   0.20000  -0.30000   0.40000  -0.50000
  -0.60000   1.30000   0.10000   1.50000
   0.90000   0.80000  -0.10000  -0.20000