Automatically set number of outputs of the gradient function

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tiwwexx 2023-8-24

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https://ww2.mathworks.cn/matlabcentral/answers/2012332-automatically-set-number-of-outputs-of-the-gradient-function

评论： tiwwexx 2023-8-29

I have a loss function I define to minimize some gradient magnitude. However, the dimension of my input data will change so I want to make my gradient have a generalized output. I have something close to a solution but Dont know how to get rid of the hard coded 2nd line below.

grad_vec = zeros([size(DATA),numel(size(DATA))]);
[grad_vec(:,:,:,1),grad_vec(:,:,:,2),grad_vec(:,:,:,3)] = gradient(DATA);
grad_mag = (sum(abs(grad_vec).^n,numel(size(DATA)))).^(1/n);

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Bruno Luong 2023-8-24

在 MATLAB Online 中打开

it probably miss a second colon on lhs

if numel(size(DATA))==2
    [grad_vec(:,:,1),grad_vec(:,:,2)] = gradient(DATA);
...

Stephen23 2023-8-24

The solution is explained here:

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/1656435-tutorial-comma-separated-lists-and-how-to-use-them

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采纳的回答

Bruno Luong 2023-8-24

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2012332-automatically-set-number-of-outputs-of-the-gradient-function#answer_1293122

编辑：Bruno Luong 2023-8-24

在 MATLAB Online 中打开

A = rand(10,10,10);
% This works for any dimensions of A
if isvector(A) % EDIT
    N = 1;
else
    N = ndims(A); % 3 in this example
end
G = cell(1,N);
[G{:}] = gradient(A);
G = cat(N+1,G{:});
size(G)
ans = 1×4
    10    10    10     3
p = 2; % whatever power in >=1
Gmag = sum(abs(G).^p,N+1).^(1/p);
size(Gmag)
ans = 1×3
    10    10    10