Generating a long vector from two other vectors

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Shoaibur Rahman
Shoaibur Rahman 2015-7-22
评论： Shoaibur Rahman 2015-7-22
I got stuck with a (may be) simple problem. Here are two vectors, like:
a = [20 13 24 ...];
b = [3 2 4 ...];
How can I create a new vector that contains 3 20s, 2 13s, 4 24s, and so on? (Not using any loop). The output will look like as shown in c:
c =
20 20 20 13 13 24 24 24 24 ...

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采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2015-7-22
编辑：Azzi Abdelmalek 2015-7-22
a = [20 13 24 ];
b = [3 2 4 ];
out=cell2mat(arrayfun(@(x,y) repmat(x,1,y),a,b,'un',0))
or with a for loop
a = [20 13 24 ];
b = [3 2 4 ];
out=zeros(1,numel(a))
c=[ 0 cumsum(b)]
for k=1:numel(a)
out(c(k)+1:c(k+1))=a(k)*ones(1,b(k))
end
  1 个评论
Shoaibur Rahman
Shoaibur Rahman 2015-7-22
Thanks a lot. It works. I read the docs of functions you have used, but was not clear about how it is working. Could you please explain the the command in brief ( out=cell2mat(arrayfun(@(x,y) repmat(x,1,y),a,b,'un',0)) )?

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更多回答（1 个）

Steven Lord
Steven Lord 2015-7-22
v = repelem([20 13 24], [3 2 4])

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