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I have a vector, where each value corresponds to a diagonal. I want to create a matrix from this vector. I have a code:

x = [1:5]; N = numel(x); diagM = diag(repmat(x(1),N,1),0); for iD = 2:N d = repmat(x(iD),N-iD+1,1); d_pos = diag(d,iD-1); d_neg = diag(d,-iD+1); d_join = d_pos+d_neg; diagM = diagM+d_join; end

It gives me what i want:

diagM = 1 2 3 4 5 2 1 2 3 4 3 2 1 2 3 4 3 2 1 2 5 4 3 2 1

But it becames really slow, for example for x=[1:10^4].

Could You help me with another FASTER way to generate such a sequence?

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Use toeplitz:

x = 1:5; diagM = toeplitz(x);

Or do it manually, vectorized:

x = 1:5; t = 1:numel(x); diagM = x(abs(t-t.')+1); % x(abs(bsxfun(@minus, t, t.'))+1) in old Matlab versions
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