resample data based on a particular variable

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Boram Lim
Boram Lim 2018-5-4
评论： Boram Lim 2018-5-4
I have a large dataset as below. From the data, I want to randomly sample based on 'id' produce the same size data. Since the data has 5 ids, I would like to sample 5 ids with replacement and produce a dataset.
id value var1 var2 …
1 1
1 2
1 3
1 4
2 5
2 6
2 7
3 8
3 9
3 10
4 11
4 12
4 13
5 14
5 15
5 16
With the data, the desired output could be as below (because I want to sample ids with replacement, there could be duplicated ids)
id value var1 var2 …
2 5
2 6
2 7
4 11
4 12
4 13
3 8
3 9
3 10
2 5
2 6
2 7
1 1
1 2
1 3
1 4
  2 个评论
KSSV
KSSV 2018-5-4
What is the difference between both the datasets? They are same.......in the second one you have repeated id 2.
Boram Lim
Boram Lim 2018-5-4
I want to randomly resample data based on id variable

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回答（1 个）

KSSV
KSSV 2018-5-4
A = [1 1
1 2
1 3
1 4
2 5
2 6
2 7
3 8
3 9
3 10
4 11
4 12
4 13
5 14
5 15
5 16 ];
id = A(:,1) ; val = A(:,2) ;
N = max(id) ;
idx = randperm(N) ;
iwant = cell(N,1) ;
for i = 1:N
iwant{i} = A(id==idx(i),:) ;
end
iwant = cell2mat(iwant)
  1 个评论
Boram Lim
Boram Lim 2018-5-4
Thank you for your comment. However, any simple way without using for-loop? my data size is around 10million and this work should be done several times.

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