如何在matlab中重复元素矩阵

Question

怎么重复

A = [ 1 2 ; 
      3 4 ]

重复

B = [ 1 2 ; 
      2 1 ]

所以我希望我的答案像矩阵C:

C = [ 1 2 2; 
      3 3 4 ]

谢谢你的帮助.

Answer 1

只是为了它的乐趣,另一个使用arrayfun的解决方案:

res = cell2mat(arrayfun(@(a,b) ones(b,1).*a, A', B', 'uniformoutput', false))'

这导致:

res =

     1     2     2
     3     3     4

Answer 2

为简单起见,我假设您只需要添加更多列,并且已经检查过每行的列数相同.

然后它成为重复元素和重塑的简单组合.

编辑我修改了代码,这样如果A和B是3D数组,它也可以工作.

%# get the number of rows from A, transpose both
%# A and B so that linear indexing works
[nRowsA,~,nValsA] = size(A);
A = permute(A,[2 1 3]);
B = permute(B,[2 1 3]);

%# create an index vector from B 
%# so that we know what to repeat
nRep = sum(B(:));

repIdx = zeros(1,nRep);
repIdxIdx = cumsum([1 B(1:end-1)]);
repIdx(repIdxIdx) = 1;
repIdx = cumsum(repIdx);

%# assemble the array C
C = A(repIdx);
C = permute(reshape(C,[],nRowsA,nValsA),[2 1 3]);

C =
     1     2     2
     3     3     4