How to crop matrix of any number of dimensions in Matlab?

Question

Suppose I have 4D matrix:

>> A=1:(3*4*5*6);
>> A=reshape(A,3,4,5,6);

And now I want to cut given number of rows and columns (or any given chunks at known dimensions).

If I would know it's 4D I would write:

>> A1=A(1:2,1:3,:,:);

But how to write universally for any given number of dimensions?

The following gives something different:

>> A2=A(1:2,1:3,:);

And the following gives an error:

>> A2=A;
>> A2(3:3,4:4)=[];

Answer 1

It is possible to generate a code with general number of dimension of A using the second form of indexing you used and reshape function. Here there is an example:

Asize = [3,4,2,6,4]; %Initialization of A, not seen by the rest of the code
A = rand(Asize);

%% This part of the code can operate for any matrix A
I = 1:2;
J = 3:4;
A1 = A(I,J,:);
NewSize = size(A);
NewSize(1) = length(I);
NewSize(2) = length(J);
A2 = reshape(A1,NewSize);

A2 will be your cropped matrix. It works for any Asize you choose.