matrix manipulation, maybe repmat?

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Zoe Zhang
Zoe Zhang 2011-7-13
I have a huge matrix, just to make the case simple
Say I have a =
1 4 7 10
2 5 8 11
And I would like to get: a =
1 4 7 10
1 4 7 10
2 5 8 11
2 5 8 11
Is there a smart way of doing that(without loop)?
Thanks in advance!!
  2 个评论
Oleg Komarov
Oleg Komarov 2011-7-13
5000 * 4 * (8 bytes) = 0.152587891 megabytes: not so huge.

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采纳的回答

Oleg Komarov
Oleg Komarov 2011-7-13
Dynamic version of the solution proposed by proecsm:
n = 2;
idx = repmat(1:size(a,1),n,1);
b = a(idx(:),:)
or
kron(A,ones(n,1))
or
http://www.mathworks.com/matlabcentral/fileexchange/24536-expand

更多回答（1 个）

bym
bym 2011-7-13
a =
1 4 7 10
2 5 8 11
>> b = a([1,1,2,2],:)
b =
1 4 7 10
1 4 7 10
2 5 8 11
2 5 8 11
  3 个评论
显示 1更早的评论
Zoe Zhang
Zoe Zhang 2011-7-13
Thanks!! Very appreciated!
Andrei Bobrov
Andrei Bobrov 2011-7-14
reshape(permute(a(:,:,[1 1]),[2 3 1]),[],4)'

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