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Flipping a matrix diagonally

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Curtis Lam
Curtis Lam 2021-7-7
评论： Isobel 2023-1-25
I would like to flip a matrix that I have diagonally from left to right as shown in the image. Is there a command or a simple way to do this? The other two ends of my matrices have the correct values so I do not want them to move

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DGM
DGM 2021-7-7
编辑：DGM 2021-7-7
Ran in:
I'm assuming you want to flip the whole matrix diagonally
To flip about the southeast-northwest diagonal is just transpose:
A = magic(5)
A = 5×5
17 24 1 8 15 23 5 7 14 16 4 6 13 20 22 10 12 19 21 3 11 18 25 2 9
A.'
ans = 5×5
17 23 4 10 11 24 5 6 12 18 1 7 13 19 25 8 14 20 21 2 15 16 22 3 9
So then flipping about the opposite diagonal is just a matter of flipping one axis:
fliplr(fliplr(A).')
ans = 5×5
9 3 22 16 15 2 21 20 14 8 25 19 13 7 1 18 12 6 5 24 11 10 4 23 17
  2 个评论
Curtis Lam
Curtis Lam 2021-7-8
I think this is close but for some reason it's not working correctly for me.. right now I have a 500x500 matrix with vertices ( the corners) looking like
[ 147 278
457 13.6]
and i want to flip/rotate the matrix so that the corners are these values so i know that the matrix is accurately representative of the raw data with corners like so:
[457 147
278 13.6]
I think I may have worded the question incorrectly but your answer might be right for the question i asked.
DGM
DGM 2021-7-8
I don't see how that's possible with any rigid transformation like a flip/transpose/rotation. The fact that adjacent corners become opposite corners leads me to question what you expect the interior of the array to look like.
Consider:
A = [147 278;
457 13];
becomes
B = [457 147;
278 13];
B is basically A' with the top row flipped. What if there were more rows?
A = [147 156 278;
124 456 583;
457 46 13];
We could transpose and then ...? How do you half-flip a row?
B = [457 124 147;
??? ??? ???;
278 583 13];
I'm not really sure what this transformation is supposed to do. I mean anything is possible with interpolation, but the question is what it means.

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更多回答（1 个）

KSSV
KSSV 2021-7-7
A = rand(5) ;
n = size(A,1) ;
v = A(1:n+1:end) ;
A(1:n+1:end) = fliplr(A(1:n+1:end))
Also read about diag.
  1 个评论
Isobel
Isobel 2023-1-25
This flips the diagonal, not the matrix along the diagonal.

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