From kron to repmat and reshape

Question

Luca Gagliardone 2017-8-4

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/351565-from-kron-to-repmat-and-reshape

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
显示 -1更早的评论隐藏 -1更早的评论

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.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Jan 2017-8-4

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/351565-from-kron-to-repmat-and-reshape#answer_276801

在 MATLAB Online 中打开

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);