MATLAB: Giving a Different Value to Elements of Array

arrayMATLAB

Hello,
I have a value for A(:,:,3,1) and another value for A(:,:,3,2). Similarly, I have different values for A(:,:,4,1) and A(:,:,4,2) But in this for loop I cant give values to elements.
How can I do that?
for i=3:basis_number
    for k =1:2
        A(:,:,i,k) = repmat(blkdiag(temp,temp2),d/4,d/4);
        A(:,:,i,k) = repmat(blkdiag(temp2,temp),d/4,d/4);
        A(:,:,i,k) = repmat(blkdiag(temp3,temp4),d/4,d/4);
        A(:,:,i,k) = repmat(blkdiag(temp4,temp3),d/4,d/4);
    end
end

Best Answer

Using numbered variables is a sign that you are doing something wrong.
In this case, using indexing would allow you to use a loop, i.e. instead of this
A(:,:,3,1) = repmat(blkdiag(temp1,temp2),d/4,d/4);
A(:,:,3,2) = repmat(blkdiag(temp2,temp1),d/4,d/4);
A(:,:,4,1) = repmat(blkdiag(temp3,temp4),d/4,d/4);
A(:,:,4,2) = repmat(blkdiag(temp4,temp3),d/4,d/4);
you can do something like this (of course you should actually just create the cell array C right from the start using basic indexing and NOT create variables with numbers in the their names):
V = 3:basis_num;
C = {[],[];[],[];temp1,temp2;temp3,temp4}; % size = basis_num * 2
A = preallocate to correct size
for ii = 3:basis_num
    x = C{ii,1};
    y = C{ii,2};
    A(:,:,ii,1) = repmat(blkdiag(x,y),d/4,d/4);
    A(:,:,ii,2) = repmat(blkdiag(y,x),d/4,d/4);
end
EDIT: based on the comments follwing this question:
n = d/2;
r = pow2(n);
C = arrayfun(@(~)rand(2,2),1:r/2,'uni',0);
% generate indices:
X = [1+eye(n);4-eye(n)];
X = fliplr([X;2+X]);
% generate output array:
%A = zeros(d,d,r,2); % preallocate!
k = 0;
for ii = 3:basis_number
    for jj = 1:2
        k = k+1;
        A(:,:,ii,jj) = blkdiag(C{X(k,:)});
    end
end
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