From kron to repmat and reshape

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Luca Gagliardone
Luca Gagliardone 2017-8-4
编辑： Luca Gagliardone 2017-8-4
I am trying to perform the same task following two different methods:
Z = 20;
W = 30;
A = 50;
size(a)
ans =
20 30
First method:
b = squeeze(a(:,1));
result1 = kron(b,ones(A,1))*ones(1,A);
size(result1)
ans =
1000 50
Second method:
b = repmat(a,[1,1,A,A]);
c = squeeze(b(:,1,:,:));
result2 = reshape(c,[Z*A,A]);
assert( all(all(result1 == result2)) )
These two methods should give the same answer, the first using kron and the second using repmat and then reshape (or some other function). The problem is that reshape and kron do not move entries in the same way, hence reshape should be substituted with something else (or differently specified). Thanks for the attention.
Sincerely Luca
  1 个评论
Jan
Jan 2017-8-4
b = squeeze(a(:,1)), but b is not used anymore. You calculate result1, but display size(c) - what is "c"? W is not used anywhere. Confusing. I cannot recreate the result with kron reliably. Please edit the question and fix the typos in the code.

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Jan
Jan 2017-8-4
Perhaps:
Z = 2;
W = 3;
A = 5;
a = rand(Z, W);
b = squeeze(a(:,1));
c1 = kron(b, ones(A,1)) * ones(1,A); % "b" instead of "a"?!
c2 = reshape(permute(repmat(reshape(a(:,1), [1,1,2]), A, A), [2,3,1]), [], A);

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