将子矩阵3d矩阵堆叠在一个矩阵中

Question

假设我有一个可变大小的三维矩阵A。是否有一个易于使用的命令，堆栈矩阵像B = [squeeze(A(1,:,:)); squeeze(A(2,:,:)); ...; squeeze(A(n,:,:))] ?

现在我使用下面的代码，但是很麻烦:

if(length(A(:,1,1))==1)
    B =squeeze(A);
else
    B = zeros(length(A(:,1,1)*length(A(1,:,1)), length(A(1,1,:)));
    B(1:length(A(1,:,1)),:) = squeeze(A(1,:,:));
    for i=2:length(A(1,:,1)
        B(1:i*length(A(1,:,1)),:)=...
            vertcat(B, squeeze(A(i,:,:)));
    end
end

Answer 1

这将做相同的B = [squeeze(A(1,:,:)); squeeze(A(2,:,:)); ...; squeeze(n,:,:))]。不确定它是否比循环快:

B = num2cell(A, [2 3]); % split along first dimension into cells 
B = permute([B{:}], [2 3 1]); % concatenate the cells along second dimension
    % and remove first dimension, which is a singleton

Answer 2

您可以将reshape与矩阵维度的排列和转置一起使用:

C = reshape(permute(A,[3,2,1]),size(A,3),[]).';

将优雅地适应任意行数。一个小测试:

A = rand([3,4,4]);
B = [squeeze(A(1,:,:)); squeeze(A(2,:,:)); squeeze(A(3,:,:))];
C = reshape(permute(A,[3,2,1]),size(A,3),[]).';
all(B(:)==C(:)) % should be true/1

Answer 3

这是另一个使用permute和reshape -

B = reshape(permute(A,[2,1,3]),[],size(A,3))