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I have generated a large dataset. Now I need to draw random samples from it. How can I do this?

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Rabeya
Rabeya 2012-11-15
For simulation, I have to draw 1000 random samples from a large dataset. I am looking for some efficient way of doing this. Can anyone help, please?

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Harshit
Harshit 2012-11-15
For dataset w
p = randperm(length(w)); % Reshuffle their order randomly
z = w(p(1:N)); % Choose the first N of these
  2 个评论
Jos (10584)
Jos (10584) 2012-11-15
编辑：Jos (10584) 2012-11-15
Note that the use of RANDPERM does not make it completely random because each original sample can only be drawn once ...
If you're after something like bootstrapping, use RANDI or RAND
Peter Perkins
Peter Perkins 2012-11-15
In recent versions of MATLAB, you can do what Harshit suggests in one line. When w is very long, this can make a difference:
z = w(randperm(length(w),N)); % select N randomly without replacement
As Jos suggests, use randi for random sampling with replacement. If you have access to the Statistics Toolbox, also see the datasample function, which allows sampling with or without replacement, and weighted or unweighted.

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Grzegorz Knor
Grzegorz Knor 2012-11-15
For example:
data = exp(-(-10:0.1:10).^2);
idx = randperm(numel(data));
N = 20;
idx = idx(1:N);
plot(idx,data(idx),'o')

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