matrix with different randperm rows

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Jeremy
Jeremy 2014-9-17
评论： Jeremy 2014-9-18
Hi,
Say I have vector of N integers, 1 through N. Is there a quick way, without loops, to create a matrix where each row is a different randperm of the vector? My N can get large (up to 100).
Thanks

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采纳的回答

Andrei Bobrov
Andrei Bobrov 2014-9-17
编辑：Andrei Bobrov 2014-9-17
[~, out] = sort(rand(M,N),2);

更多回答（3 个）

Guillaume
Guillaume 2014-9-17
cell2mat(arrayfun(@(dummy) randperm(n), 1:m, 'UniformOutput', false)');
Whether or not that can be said to be without a loop is debatable as arrayfun is effectively looping over the array 1:m
Mikhail
Mikhail 2014-9-17
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Image Analyst
Image Analyst 2014-9-17
In what universe, or decade, is 100 considered large? You actually mean 100, right, like ten times ten, not 100 million or 100 billion or something?
Jeremy
Jeremy 2014-9-17
100 is large when you talk about some types of group coordination. I need to select k individuals from a group of N to interact at different time steps. What I've been doing is generating all combinations and randomly selecting ones to fill an interaction matrix, but that combination matrix gets big fast.

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Joseph Cheng
Joseph Cheng 2014-9-17
Well there is a randperm() function that will give you a random permuation. How to get it as a MxN matrix without a loop will take some more time to think about it.
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Joseph Cheng
Joseph Cheng 2014-9-17
编辑：Joseph Cheng 2014-9-17
ok well it is possible to do it without a loop in 2ish lines. Use the function arrayfun() or cellfun() on an array of N*ones(M,1).

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