creating multi-dimensional arrays from vectors

Question

Pal 2012-3-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/33552-creating-multi-dimensional-arrays-from-vectors

采纳的回答： Geoff

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Hi,

I want to create a multi-dimensional array 'b' from a vector 'a' as the following example:

a =

1 2 3 4

b(:,:,1) =

     1     1
     1     1

b(:,:,2) =

     2     2
     2     2

b(:,:,3) =

     3     3
     3     3

b(:,:,4) =

     4     4
     4     4

Thus I want to copy each entry of 'a' as m by n (2 by 2 in the example) size matrices onto each level of 'b' along the third dimension. I need to avoid element-wise operations and be as fast as possible.

I would appreciate any help.

Thank you.

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Answer 1

Geoff 2012-3-27

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https://ww2.mathworks.cn/matlabcentral/answers/33552-creating-multi-dimensional-arrays-from-vectors#answer_42164

在 MATLAB Online 中打开

[~,~,b] = ndgrid([0 0], [0 0], a)

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Pal 2012-3-27

Thanks! What are the tilde symbols? I have never seen them in Matlab syntax.

Geoff 2012-3-27

They are a placeholder, meaning we don't care about a particular return value. It's the way to get the third return value into 'b' without assigning the first and second return values to a variable.

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