Extracting every n number of column from matrix matlab

Question

Aybars 2018-5-3

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评论： Ameer Hamza 2018-8-16

0 down vote favorite I need to extract every n number of column from my matrix. Please note that not every nth column. For example I have a matrix:

A =
     1    23    34    53    67    45    67    45
    12    34    45    56    67    87    98    12
     1     2     3    45    56    76    87    56
And I want to extract each 3 column, so my data should be like:
X =
     1    23    34    67    45    67
    12    34    45    67    87    98
     1     2     3    56    76    87
So I would skip 4th column then 8th column and so on. I know how to extract every nth column and row but I couldn't figure it out what I need. Appreciated for your help

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Answer 1

Ameer Hamza 2018-5-3

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编辑：Ameer Hamza 2018-5-3

在 MATLAB Online 中打开

Here is a general solution to your problem in which you can specify how many columns to keep and how many to delete

colToKeep = 2;
colToDelete = 3;
ColIndex = mod( 0:size(A,2)-1, colToKeep+colToDelete ) < colToKeep;
A(:, ~ColIndex) = [];

Use colToKeep and colToDelete to specify the values.

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Ee Woon Lim 2018-8-16

How do we do this for rows?

Ameer Hamza 2018-8-16

Just take the transpose of the matrix and apply the same method. At the end take the transpose again to get the correct matrix.

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Answer 2

Yuvaraj Venkataswamy 2018-5-3

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编辑：Yuvaraj Venkataswamy 2018-5-3

在 MATLAB Online 中打开

Answer is below where A is a your matrix.

if true
  n=4;
  A =[1    23    34    53    67    45    67    45
    12    34    45    56    67    87    98    12
     1     2     3    45    56    76    87    56]
    A(:,n:n:end) =[]
end

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Aybars 2018-5-3

Hi, Thank you very much for your answer. It is correct. But in that case, how can I adjust the number of column that I want to skip ? For example I would like to take first 2 columns, then skip 3 columns then take 2 columns again.

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Answer 3

Guillaume 2018-5-3

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https://ww2.mathworks.cn/matlabcentral/answers/398810-extracting-every-n-number-of-column-from-matrix-matlab#answer_318455

在 MATLAB Online 中打开

X = A;
X(:, 4:4:end) = [];

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Aybars 2018-5-3

Hi, Thank you very much for your answer. It is correct. But in that case, how can I adjust the number of column that I want to skip ? For example I would like to take first 2 columns, then skip 3 columns then take 2 columns again.

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