How do you create an array with multiple rows in one line?

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Perplumblewintz
Perplumblewintz 2020-12-17
评论： Cris LaPierre 2020-12-17
I'm struggling with something that seems like it should be very simple. I'm trying to create an array of 3x3 matrices. I see that I can do something like:
A = [1,2,3; 4,5,6; 7,8,9]
A(:,:,2) = [9,8,7; 6,5,4; 3,2,1]
How do I do that in one line? I thought that something like this would work:
A = [[1,2,3; 4,5,6; 7,8,9]; [9,8,7; 6,5,4; 3,2,1]]
But that creates a 6x3 matrix. And this creates a 3x6 matrix:
A = [[1,2,3; 4,5,6; 7,8,9] [9,8,7; 6,5,4; 3,2,1]]
I've tried other variations and read documentation, but am at a loss here. Any help would be appreciated. Thanks!

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Cris LaPierre
Cris LaPierre 2020-12-17
编辑：Cris LaPierre 2020-12-17
Ran in:
I'm not aware of a shorthand way to do this. You can consult the documentation here.
One way could be to use reshape followed by a transpose. Not sure that really buys you anything, though.
A = pagetranspose(reshape([1,2,3, 4,5,6, 7,8,9, 9,8,7, 6,5,4, 3,2,1],3,3,2))
A =
A(:,:,1) = 1 2 3 4 5 6 7 8 9 A(:,:,2) = 9 8 7 6 5 4 3 2 1
Another option is to use cat to combine the two matrices in the 3rd dimension.
A2 = cat(3,[1,2,3; 4,5,6; 7,8,9], [9,8,7; 6,5,4; 3,2,1])
A2 =
A2(:,:,1) = 1 2 3 4 5 6 7 8 9 A2(:,:,2) = 9 8 7 6 5 4 3 2 1
  2 个评论
Perplumblewintz
Perplumblewintz 2020-12-17
Oh, wow. Okay, I guess I mmight be thinking about this wrong for matlab (as a programmer) :)
Thanks!
Cris LaPierre
Cris LaPierre 2020-12-17
It's just a matter of learning what is possible. There are shortcuts for creating 1D and 2D arrays, but not 3D.

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