How to do a cycle through a N-dimensional grid, if n is not fixed?

2 次查看（过去 30 天）

Mr M. 2017-12-11

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/372299-how-to-do-a-cycle-through-a-n-dimensional-grid-if-n-is-not-fixed

编辑： Stephen23 2022-2-9

I know there is ngrid, but you have to know n. What if I want to do n for cycles, but I don't know n at the moment, it is a variable.

2 个评论
显示无隐藏无

Mr M. 2017-12-11

And one additional thing. Since number of gridpoints can be very large. It would be nice to have a solution where you don't want to store the gridponts, just go through them!

Stephen23 2017-12-11

Mr M.'s "Answer" moved here:

I would like to go through the grid points of an N-dimensional grid, but N is an input parameter. For example in each dimension I would like K gridponts, so I have KxKxKx...xK = K^N points. If i know that N=2, I can use meshgrid, or in case of N=5, I can use [X1,X2,X3,X4,X5] = ngrid(1:K,1:K,1:K,1:K,1:K); But N is a variable! How to go through the gridpoints?

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Guillaume 2017-12-11

4
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/372299-how-to-do-a-cycle-through-a-n-dimensional-grid-if-n-is-not-fixed#answer_295703

编辑：Guillaume 2017-12-11

在 MATLAB Online 中打开

Please don't use answer boxes when commenting. Use the Comment on this Question or comment on this Answer box.

If I understood you want to generate N Nd arrays with ndgrid with N being unknown in advance. No problem, use the expansion of cell arrays into comma-separated lists to do that:

N = 5;  %value can change
K = 4;  %value can change
Ndarrays = cell(1, N);  %create cell array to receive outputs of ndgrid
[Ndarrays{:}] = ndgrid(1:K);  %fills all N Nd arrays

And in case, your K is different for each dimension, then:

N = randi([3 6]);  %randomly chose N between 3 and 6. For demo
K = randi([2 7], 1, N);  %randomly chose N K  between 2 and 7. For demo
sizeinputs = arrayfun(@(k) 1:k, K, 'UniformOutput', false);  %generate the inputs of ndgrid as a cell array
ndarrays = cell(1, N);
[ndarrays{:}] = ndgrid(sizeinputs{:});