Matlab：我可以创建一个维数未知的矩阵吗？

Question

Normally a matrix has 2 dimensions, but there doesn't seem to be a limit on the number of dimensions a matrix may have in MATLAB.

To create a 4-dimensional matrix, for example, I can do this:

>> x = zeros(2,2,2,2)

x(:,:,1,1) =

     0     0
     0     0


x(:,:,2,1) =

     0     0
     0     0


x(:,:,1,2) =

     0     0
     0     0


x(:,:,2,2) =

     0     0
     0     0

Is there a way to create a matrix of which the number of dimensions is only known at runtime?

Answer 1

You could call zeros like this:

x = zeros([2 2 2 2])

Hence, you can customize the input array as you want.

For example: to create a 2x2x2x2x2 matrix (where D = 5, the number of dimensions):

D = 5;
x = zeros(zeros(1, D) + 2)

Answer 2

Rafael's answer hits the nail on the head. But there's also a general way to do this sort of thing even when the function doesn't have an overload for something like a vector input as in the case of zeros . You can use a cell array like so:

>> dims = {2,2,2,2};
>> zeros(dims{:})
ans(:,:,1,1) =

     0     0
     0     0


ans(:,:,2,1) =

     0     0
     0     0


ans(:,:,1,2) =

     0     0
     0     0


ans(:,:,2,2) =

     0     0
     0     0

I've found this approach to be very useful for other functions.

Edit:

This approach is more robust. Here's another example:

imginfo = { rand(40), [0 1], 'Colormap', colormap(jet) };
figure, imshow(a{:});