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

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?

Answer 1

[Harshit]

 For dataset w

     p = randperm(length(w)); % Reshuffle their order randomly
     z = w(p(1:N)); % Choose the first N of these

[Jos (10584)]

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]

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.

Answer 2

[Grzegorz Knor]

For example:

data = exp(-(-10:0.1:10).^2);

idx = randperm(numel(data));
N = 20;
idx = idx(1:N);

plot(idx,data(idx),'o')