Combine cell array with contant matrices

Hi everyone,

Suppose I have a cell array A{1} A{2} A{3} ... A{n}, can I create a new cell array A_{1} A_{2} A_{3} ... A_{n}, such that A_{1}=[0 0 0;0 A{1} 0;0 0 0], A_{2}=[0 0 0;0 A{2} 0;0 0 0], A_{n}=[0 0 0;0 A{n} 0;0 0 0], without loop?

Is there any efficient way to perform this operation?

P.S. A{1:n} are all same size matrices, 0 represents a zero matrix.

thanks

Answer 1

[Matt J]

No, there is no way to avoid loops when working with cell arrays (including those hidden in cellfun). However, if you are storing things in cell arrays, it probably means your data isn't large enough to make efficiency a very big concern.

If A{1:n} are all same size matrices, it would have served you better to store them as a 3D array,

   A3d=cat(3,A{:});

You could then create a similar, zero-padded 3d array by doing,

A3d_=zeros(...);
A3d_(i:j,m:n,:)=A3d;

Answer 2

[Andrei Bobrov]

A1 = cat,3(A{:});
A2 = zeros(size(A1)+[2,2,0]);
A2(2:end-1,2:end-1,:) = A1;
A_ = reshape(num2cell(A2,[1,2]),[],1);

[Matt J]

num2cell has hidden for loops in it...