How do I select elements out of a matrix with a loop?

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Gerdur Gardarsdottir 2013-9-25

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Hi, please help. I have a 16x16 matrix where I need to pick a 16 elements out for a 4x4 matrix. (Guyan reduction) I don't know how to make loops jet. /Klara

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Answer 1

David Sanchez 2013-9-25

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在 MATLAB Online 中打开

You can try the following:

A = rand(16); % a 16x16 random matrix
B = reshape(M,4,4,16);  % you will get 16 4x4 matrices. To access these matrices:
for k=1:16
  B(:,:,k);
end

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Gerdur Gardarsdottir 2013-9-25

Thank you very much for your answear. But I have 16 dof (16x16)matrix and I need to be able to retain some dof´s e.g. (3 7 11 15) and out them into a 4x4 matrix and then have the omitted in a 12x12 and retian,omitted in an 4x12. I just don-t know how to "pick out" the retained after I have defined them :(.

Jan 2013-9-25

编辑：Jan 2013-9-25

@Gerdur: I do not understand your question. While many readers are not familiar with the "Guyan reduction", you are. So please explain it as clear as possible. What does this mean: "have the omitted in a 12x12 and retian,omitted in an 4x12"?

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