How to Copy Upper diagonal elements of matrix A into a new matrix.

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Usman Mussadiq
Usman Mussadiq 2021-9-14
评论： Usman Mussadiq 2021-9-14
A= 1 2 3 4; 2 1 3 4; 1 1 1 2; 1 0 0 1 Then how to copy the upper diagonal elements into a new Matrix using for loops etc.

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Jan
Jan 2021-9-14
Ran in:
A = [1 2 3 4; 2 1 3 4; 1 1 1 2; 1 0 0 1];
B = triu(A)
B = 4×4
1 2 3 4 0 1 3 4 0 0 1 2 0 0 0 1

更多回答（2 个）

Awais Saeed
Awais Saeed 2021-9-14
编辑：Awais Saeed 2021-9-14
Ran in:
A= [1 2 3 4; 2 1 3 4; 1 1 1 2; 1 0 0 1]
A = 4×4
1 2 3 4 2 1 3 4 1 1 1 2 1 0 0 1
M = zeros(size(A));
for row = 1:1:size(A,1)
for col = row:1:size(A,2)
M(row,col) = A(row,col);
end
end
disp(M)
1 2 3 4 0 1 3 4 0 0 1 2 0 0 0 1
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Awais Saeed
Awais Saeed 2021-9-14
I answered exactly as per your question "how to copy the upper diagonal elements into a new Matrix using for loops".
Why do you care how your developer is doing things. If you think he is making a mistake or he needs help in doing what you asked in your question then just simply show him the proposed answer. If he does not like doing it in a For Loop then use triu(A) as @Jan have mentioned.

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KSSV
KSSV 2021-9-14
You need to proceed like this:
for i = 1:m
for j = 1:n
if i <= j
end
end
end
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Usman Mussadiq
Usman Mussadiq 2021-9-14
@Jan it is mentioned by the algo developer that he is copying the upper diagonal elements into temp, but in my understanding this code is generating a full matrix from the upper triangular elements only. Please guide me.
Jan
Jan 2021-9-14
I do not know what "copy into temp" means.
Maybe you want to get a vector with only the elements of the upper triangular matrix?
mask = (1:4) > (1:4).'; % Or >= ?
temp = A(mask)

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