How can I rotate a part of a matrix

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DM
DM 2020-9-24
评论： Ameer Hamza 2020-9-24
Hi there,
I have a 4D images (dimensions [156 192 26 42]). I would like to rotate only the last 20 volumes of my 4D matrix and keep the first as it is.
I tried the following:
rotated_matrix=original_matrix;
rotated_matrix = rot90(original_matrix(:,:,:,23:42));
The rotated_matrix has been rotated but it has dimensions [192 156 26 20]. Basically it contains the volumes that have been rotated.
How can I rotate only the volume in the last 20 places and keep the first 22 as they are?

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回答（1 个）

Ameer Hamza
Ameer Hamza 2020-9-24
Try something like this
rotated_matrix = original_matrix(:,:,:,[1:20 42:-1:21]);
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DM
DM 2020-9-24
I might have put my question wrong. I didn't want to reverse the order of the last 20 elements.
I wanted to replace the last 20 elements in the 4th dimension of the original matrix with the 20 elements of the rotated_matrix.
Origina matrix has dimensions [156 192 26 42] where the rotated matrix has dimensions [156 192 26 20].
What I wanted to do is to replace the last 20 elemets of the original matrix with the 20 elemets of the rotated matrix.
Ameer Hamza
Ameer Hamza 2020-9-24
Ok. I get it know. Following will work for this case
original_matrix(:,:,:,end-19:end) = rotated_matrix

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