rand('seed',1)

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hi there, can anyone explain me the different between using 'rand('seed',1)' inside the loop and outside the loop? Assuming I generate some random number inside the loop.

Ta,Rak

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Answer 1

Jan 2011-11-30

在 MATLAB Online 中打开

4 个投票

Seeding the random number generator means initializing it to a certain status. Seeding inside the loop means, that all "random" numbers created inside the loop will be the same in each iteration:

for i = 1:3
  rand('seed', 1);
  disp(rand);
end

Result: 0.51291 0.51291 0.51291

This is not very useful. Seeding RAND outside the loop allows you to reproduce the results:

for j = 1:2
  rand('seed', 1);
  for i = 1:3
    disp(rand);
  end
end

Now you get two series of 3 different numbers:

0.51291 0.46048 0.3504 0.51291 0.46048 0.3504

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Ricky 2011-12-1

got it now, thanks alot

Peter Perkins 2011-12-1

Unless you are using an extraordinarily old (from the early 1990's) version of MATLAB, you should not be using rand('seed',1) at all. It most likely does not do what you think it does. If you are using R2011a or newer, see this:

<http://www.mathworks.com/help/techdoc/math/bs1qb_i.html>

Otherwise, see the documentation in whatever version you are using.

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