Reshape 1D to 3D array

24 次查看（过去 30 天）
John Cruce
John Cruce 2023-8-5
评论： John Cruce 2023-8-6
I have a 1D array (365x1) that I need to reshape into a 3D array (365x1x1) to divide into 3D array (365x721x1440). What's the most efficient means of accomplishing this task?

请先登录，再回答此问题。

回答（1 个）

the cyclist
the cyclist 2023-8-5
Ran in:
MATLAB arrays implicitly have length-1 dimensions after the defined dimensions. For example
% Define 365x1 array
M = rand(365,1);
% Length in 3rd dimension
size(M,3)
ans = 1
% Length in 31st dimension
size(M,31)
ans = 1
Regarding how that ends up being (365x721x1440), you'll need to provide more detail.
  4 个评论
显示 2更早的评论
DGM
DGM 2023-8-6
编辑：DGM 2023-8-6
Ran in:
I think we're getting confused by the suggestion of "reshaping". The way it appears to me, reshaping A is not necessary. It appears as this is simply a misunderstanding how to make array sizes compatible for arithmetic operations. Consider the example:
A = (1:4).' % a column vector
A = 4×1
1 2 3 4
B = 2*ones(4,4,2) % a 3D array with the same page height
B =
B(:,:,1) = 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 B(:,:,2) = 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
% you could expand A to have the same size as B
% A = repmat(A,[1 4 2]);
% but it's not necessary
A./B
ans =
ans(:,:,1) = 0.5000 0.5000 0.5000 0.5000 1.0000 1.0000 1.0000 1.0000 1.5000 1.5000 1.5000 1.5000 2.0000 2.0000 2.0000 2.0000 ans(:,:,2) = 0.5000 0.5000 0.5000 0.5000 1.0000 1.0000 1.0000 1.0000 1.5000 1.5000 1.5000 1.5000 2.0000 2.0000 2.0000 2.0000
So long as the arrays are compatibly-sized along their non-singleton dimensions, you should be able to perform elementwise arithmetic without explicitly expansion. If you were running a version older than R2016b, the recommended method would be to use bsxfun() instead of repmat().
Of course, I might be interpreting the question wrong.
John Cruce
John Cruce 2023-8-6
You're excatly right. I was definitely overcomplicating it.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Matrix Indexing 的更多信息

标签

产品


版本

R2023a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by