MATLAB: How to make matrix of ones and zeros alternating depending on size and elements of an array

MATLABmatrix

I have an array, A, and I want to make a matrix, B, that has the size dependent on A, and has 1s and 0s alternating, depending on the value of elements in A
E.g. A=[1;2;3;4;5]
B should be of size: ((length(A)+1)/2,sum(A)]
In this case B would be a matrix of 3×15
Then the values for B needs to be be thus:
row 1:[ones(A(1)),zeros(A(2)),zeros(A(3)),zeros(A(4)),zeros(A(5))]
row2: [zeros(A(1)),zeros(A(2)),ones(A(3)),zeros(A(4)),zeros(A(5))]
row3: [zeros(A(1)),zeros(A(2)),zeros(A(3)),zeros(A(4)),ones(A(5))]
B should look like:
[1 0 0 0 0 0 0 0 0 0 0 0 0 0 0;
0 0 0 1 1 1 0 0 0 0 0 0 0 0 0;
0 0 0 0 0 0 0 0 0 0 1 1 1 1 1]
I've been trying to formulate something with a nested for look for each dimension of B, but have not been succesful!
Would really appreciate any help thanks!

Best Answer

% initialize
iRow = [];
jCol = [];
% preallocate
B = zeros((length(A)+1)/2,sum(A));
% indices for columns
idx = [0; cumsum(A)]+1;
for i = 1:length(A)
    if mod(i,2) ~= 0
        iRow = [iRow; repmat((i+1)/2,A(i),1)];
        jCol = [jCol; (idx(i):idx(i+1)-1).'];
    end
end
B(sub2ind(size(B),iRow,jCol)) = 1;
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