How to mirror matrix on the diagonal?

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SL
SL 2016-10-21
编辑： DGM 2022-8-3
I want to mirror data matrix on the diagonal.
Input:
y
|
____ x
Expected output:
x
|_y
I know you these transformations but I cannot get mirror around the diagonal (y=x line from (0,0) to (1,1))
I = imread('onion.png');
I2 = flipdim(I ,2); %# horizontal flip
I3 = flipdim(I ,1); %# vertical flip
I4 = flipdim(I3,2); %# horizontal+vertical flip
MATLAB: 2016b OS: Debian 8.5
  2 个评论
Massimo Zanetti
Massimo Zanetti 2016-10-21
Can you give a simple example with numeric array of the "mirroring" you need? Is it something like:
1 2 3
4 5 6
7 8 9
to
9 6 3
8 5 2
7 4 1
?

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采纳的回答

Thorsten
Thorsten 2016-10-21
I2 = rot90(fliplr(I),-1);
  3 个评论
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Emmanuel Atoleya Atindama
Emmanuel Atoleya Atindama 2022-8-3
Yes. This works on n-d arrays. The other answers involving transpose do not work in arrays greater than 2 dimensions, unless you want to iterate thru the other dimensions.
DGM
DGM 2022-8-3
To add to the confusion, depending on what version you use, this may still not work with arrays that are more than 2D. In older versions, rot90(), fliplr() and flipud() are limited to work only on 2D arrays. It might not be that relevant today, but this is not a current thread.

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更多回答（2 个）

Massimo Zanetti
Massimo Zanetti 2016-10-21
编辑：Massimo Zanetti 2016-10-21
In the case described before it is:
A=[1 2 3;4 5 6;7 8 9]
rot90(A,2)'
which gives:
A= 1 2 3
4 5 6
7 8 9
to
9 6 3
8 5 2
7 4 1
  3 个评论
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Massimo Zanetti
Massimo Zanetti 2016-10-22
I can't see why it shouldn't work... You must give me an example, otherwise I cannot understand. No problems with rectangular matrices.
DGM
DGM 2022-8-3
编辑：DGM 2022-8-3
Ran in:
The transpose operator doesn't work on anything other than a 2D array, but you can still use permute().
A = repmat([1 2 3;4 5 6;7 8 9],[1 1 3])
A =
A(:,:,1) = 1 2 3 4 5 6 7 8 9 A(:,:,2) = 1 2 3 4 5 6 7 8 9 A(:,:,3) = 1 2 3 4 5 6 7 8 9
B = permute(rot90(A,2),[2 1 3]) % use permute()
B =
B(:,:,1) = 9 6 3 8 5 2 7 4 1 B(:,:,2) = 9 6 3 8 5 2 7 4 1 B(:,:,3) = 9 6 3 8 5 2 7 4 1
C = pagetranspose(rot90(A,2)) % or use pagetranspose() (R2020b or newer)
C =
C(:,:,1) = 9 6 3 8 5 2 7 4 1 C(:,:,2) = 9 6 3 8 5 2 7 4 1 C(:,:,3) = 9 6 3 8 5 2 7 4 1
That said, if the OP isn't aware of the array dimensionality, then there are probably other problems.

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Fady Samann
Fady Samann 2020-8-13
you can do the following:
first, transpose the matrix
A = table.';
Flip it horizontally
A = flip (A,1);
then, flip it verticaly
A = flip (A,2);

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