Take samples from the previous sample

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Ellie
Ellie 2015-8-10
编辑： Star Strider 2015-8-10
Hi all, I have set of data, the size doesn't really matter. Lets call it x1. I want to take a random set of values from x1 and lets call it x2. Then take random samples from x2 and call it x3. So on and so forth. I am not really sure how to do this, I have tried a couple of things, but without luck. Any help is appreciated. Also, I have access to the statistics library. The things that I have tried made use of the function randsample.
Thanks.
  2 个评论
Azzi Abdelmalek
Azzi Abdelmalek 2015-8-10
Can you give more details? how many sample? when do you want to stop?
Ellie
Ellie 2015-8-10
It doesn't really matter, but for arguments sake: sample size 100, and stop at 10.

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采纳的回答

Star Strider
Star Strider 2015-8-10
I’m not certain what you want, but this is one possibility:
x1 = randsample(99, 15)'
x2 = x1(randsample(15,10))
x1 =
76 68 83 17 87 16 35 30 53 62 26 38 8 98 40
x2 =
8 53 40 38 17 83 26 62 35 30
The only constraint is to be certain that in ‘x2’ and beyond, the first argument to randsample is not greater than the length of the vector created in ‘x1’ or the earlier vectors.
  2 个评论
Ellie
Ellie 2015-8-10
That is the desired output, but how could I make it more general. For example, if I want to do that 10 times, I don't want to have to do that over and over.
Star Strider
Star Strider 2015-8-10
编辑：Star Strider 2015-8-10
One option is to put it into a loop:
x{1} = randsample(99, 15)';
for k1 = 2:10
x{k1} = randsample(x{k1-1},15);
end
All the vectors are the same sizes, but since they are cells, you can experiment with them to get the result you want.
EDIT — To use randsample with replacement, include the third argument as true or 1.

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更多回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2015-8-10
x=1:100
k=1;
out{k}=x
while numel(out{k})>10
n=numel(out{k});
idx=randperm(n-1);
out{k+1}=out{k}(idx);
k=k+1;
end
celldisp(out)
  2 个评论
Ellie
Ellie 2015-8-10
Is there a way to do this with replacement?
And maybe without using cells?
Azzi Abdelmalek
Azzi Abdelmalek 2015-8-10
the new samples have different sizes, you can't avoid cells. Why do you want to avoid cells?

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