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How to call columns of matrices using 'for loop' ?

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Khan
Khan 2021-4-15
评论： Khan 2021-4-15
Hello,
I am new to MATLAB, can anyone tell me how can I use for loop for the following formulas?
Approx1=U(:,1)*S(1)*V(:,1)';
Approx2=U(:,1)*S(1)*V(:,1)'+ U(:,2)*S(2)*V(:,2)';
Approx3=U(:,1)*S(1)*V(:,1)'+ U(:,2)*S(2)*V(:,2)'+ UU(:,3)*S(3)*V(:,3)';
where U is 6 x 3, S is diagonal (3 x 3) and V is a 3 x 3 matrix. 1, 2 3 are being the columns of respective matrices.
Thank you
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Matt J
Matt J 2021-4-15
I want to Multiply first coulmn of U, S and V' matrices and then multiply second coulms of U, S and V' matrices
No, you can't because the columns of all these matrices have different lengths. You therefore cannot multiply their columns together.
Aren't you simply doing KL-transforms with different truncations? If so, that is what my answer below gives you, (and you should Accept-click it).

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采纳的回答

Matt J
Matt J 2021-4-15
编辑：Matt J 2021-4-15
for i=1:3
Approx{i}= U(:,1:i)*S(1:i,1:i)*V(:,1:i).';
end
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Khan
Khan 2021-4-15
编辑：Khan 2021-4-15
dear, it is not working. actually in the first Approximation I want to Multiply, first coulmns of U, S and V' matrices. In the Second approximatrion, I want to Multiply first coulmn of U, S and V' matrices and then multiply second coulms of U, S and V' matrices, and then add them. Simillarly for the last approximation. I want to get three different approximations.

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更多回答（1 个）

David Hill
David Hill 2021-4-15
s=diag(S);
for i=1:3
Approx(:,:,i)=U(:,i)*V(:,i)'*s(i);%I am assuming this is what you want, s(i) being scalar along the diagonal
end
Approx=cumsum(Approx,3);
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David Hill
David Hill 2021-4-15
Hopefully you realize that S(1) is scalar and the first element in the diagonal matrix, S(2) will be zero, and S(3) will be zero. You are not multiplying by the column of S. The below produces the same result as expected.
for i=1:3
Approx(:,:,i)=U(:,i)*V(:,i)'*S(i);
end
Approx=cumsum(Approx,3);

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