How to produce data randomly from a given matrix without changing the dimension

Question

Tinkul 2014-4-6

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回答： Jos (10584) 2014-4-7

I have some data for eg

A=[1;3;5;7;2]

Now i have to produced all these data randomly. Is there any matlab command to produce these data randomly without changing the dimension...Please help...

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Answer 1

Jan 2014-4-6

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编辑：Jan 2014-4-6

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Perhaps you mean something like this:

   A = [1;3;5;7;2]
   for k = 1:10
     A = A(randperm(length(A)))
   end

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Answer 2

Image Analyst 2014-4-6

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Yes. It's a 5 row column vector. Of course it's possible to produce it, it just depends on what you mean by randomly. Do you just want to keep using randi(7,5) until your number match those? Like this:

A=[1;3;5;7;2]
% Use a Monte Carlo approach to generate A randomly
count = 1;
while count < 10000000
  rv = randi(7, [5, 1]);
  difference = abs(rv-A);
  if max(difference) == 0
    break;
  end
  count = count + 1;
end
message = sprintf('Found it after %d iterations', count);
uiwait(helpdlg(message));

Please clarify.

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Tinkul 2014-4-6

Suppose A=[1;3;5;7;2] I mentioned randomly, which means

A1=[1;7;3;5;2] or A1=[2;5;1;3;7] etc.etc.. That means the row of A1 matrix have the value which is also in A but in different row.

Image Analyst 2014-4-7

This would have been helpful to include in your original post, don't you think? But it looks like Jan's code does what you want.

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Answer 3

Jos (10584) 2014-4-7

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Do you want a random permutation or a random derangement (i.e., none of the elements stays in place, as suggested by your comment to Image Analyst)?

% random permutation
B = A(randperm(numel(A))
% random derangement 
B = A ;
if numel(A)>1
   while any(B==A) % a rejection method
      B = A(randperm(numel(A)) ;
   end
else
   disp('No derangement possible.')
end