How can I store the values of a diagonal using only a for loop?

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Jonas Morgner 2022-5-4

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https://ww2.mathworks.cn/matlabcentral/answers/1711440-how-can-i-store-the-values-of-a-diagonal-using-only-a-for-loop

编辑： Walter Roberson 2022-5-4

%A
rng('default')
r2 = randi(100,3,3); % Creating a 3x3 matrix, with random values from 1 to 100
%B
d = diag(r2) % Obtain the diagonal elements 
%C
Metod1 = d(2,1) % Using two parameters (row 2, column 1)
Metod2 = d(3) % Using one parametr (3rd element)

How can I create a new vector which only stores the diagonal using a for loop from the initial matrix?

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Answer 1

Walter Roberson 2022-5-4

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https://ww2.mathworks.cn/matlabcentral/answers/1711440-how-can-i-store-the-values-of-a-diagonal-using-only-a-for-loop#answer_956820

If you loop from 1 to the minimum of the number of rows or columns, then for iteration K the element is at d(K,K)

If you want to use linear indexing, then note that once you know where one element of the diagonal is, that the next one is (rows + 1) elements further along. For example, 3 x 3, rows+1 is 4, and the diagonals are at (1), (1+4), (1+4+4)

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Jonas Morgner 2022-5-4

First of all thak you fo the explanation, I now can understand this in theroy. However I am really new to programming and I dont know how to translate this into code. Could you help me with that?

Walter Roberson 2022-5-4

编辑：Walter Roberson 2022-5-4

在 MATLAB Online 中打开

for K = 1 : size(d,1)
    d(K,K)
end

after that it becomes a matter of how to store the K'th value into the K'th element of a vector. If that is not something you are familiar with you should be considering running through MATLAB Onramp.

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