Delete certain entries in a 3D matrix

OK, so I have a 4 page 3x30 3D matrix (which is 3x30x4) and would like to delete certain entries in matrix. These entries are the same on all 4 pages and the entries are stored in a 1x30 matrix like:

idx = [1     1     3     3     3     3     3     3     1     1     1     1     1     1     1     1     1     1     1     1     1     2     2     2     2     2     2     2     2     2]

such that each entry in idx corresponses to the entry needed to be delete in each column. By say delete, I mean assigning a [ ] to the entry. To further illustrate let's say I have a 3D matrix A and idx:

A(:,:,1) = [1 2 3; 
            4 5 6; 
            7 8 9]
        
A(:,:,2) = [10 11 12; 
            13 14 15; 
            16 17 18]
        
A(:,:,3) = [19 20 21; 
            22 23 24; 
            25 26 27]

idx = [3 2 2]

I would like to get a 2x3x3 matrix B in this context:

B(:,:,1) = [1 2 3; 
            4 8 9]
        
B(:,:,2) = [10 11 12; 
            13 17 18]
        
B(:,:,3) = [19 20 21; 
            25 23 24]

Are there any methods that can do this without a loop?

Answer 1

[Andrei Bobrov]

A = randi(200,3,30,4);% Let A - our array [3 x 30 x 4]
idx = [1,1,3,3,3,3,3,3,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2]';

[m,n,k] = size(A);
[i,j] = ndgrid(1:n,1:k);
A(sub2ind([m,n,k],repmat(idx(:),1,k),i,j)) = [];
B = reshape(A,m-1,n,[]);

[Douglas Chiang]

Thanks Andrei, this is exactly what I want :)

Answer 2

[Rik]

I'm assuming the last page of your example is incorrect.

clear A
A(:,:,1) = [1 2 3; 
            4 5 6; 
            7 8 9];
        
A(:,:,2) = [10 11 12; 
            13 14 15; 
            16 17 18];
        
A(:,:,3) = [19 20 21; 
            22 23 24; 
            25 26 27];

idx = [3 2 2];

sz=size(A);
rowsub=repmat(idx,1,sz(3));
colsub=repmat(1:sz(2),1,sz(3));
pagesub=repelem(1:sz(3),1,sz(2));
ind=sub2ind(sz,rowsub,colsub,pagesub);

B=A;
B(ind)=[];
szB=sz-[1 0 0];
B=reshape(B,szB)

[Douglas Chiang]

Thanks for your answer :)