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split dataset with probability weights

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Genz
Genz on 15 Oct 2019
Commented: Genz on 15 Oct 2019
Hello everyone
i have a dataset like 20 x 6. i want to split dataset (npop1) into two dataset which depend on probabbility 'weights'. the probability comes from random number r1. i can't figure out how to store the rest data into another variable dataset (rw2). I don't use randperm because randperm has no probability function. I will appreciate any help. Thank you.
Sorry for my bad English..
pc = 0.4; %percentage to split data
nfitA = length(fitA);
PC = pc*npop;% make positive interger
r1 = rand (nfitA,1); %random number for weight probability
rw1 = datasample(npop1,PC,'Weights',r1);

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Accepted Answer

Fabio Freschi
Fabio Freschi on 15 Oct 2019
datasample has a two outputs, where the second is the index to the selected data in your npop1. So:
[rw1,idSelected] = datasample(npop1,PC,'Weights',r1);
idUnselected = setdiff(1:nfitA,idSelected);
rw2 = npop1(idUnselected,:);

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Genz
Genz on 15 Oct 2019
sorry sir, i am not quite understand. but fitA only contain 10x1. fitA is data from another file.
split data only on npop1 data (10x6).
Fabio Freschi
Fabio Freschi on 15 Oct 2019
Got the point! As Jos highlighted, datasample samples with replacement. This means that each sample can be selected more than once. see for example this link.
If you don't want the replacement, you must instruct datasample in this way:
[rw1,idSelected] = datasample(npop1,PC,'Weights',r1,'Replace',false);
You can leave the rest of the code unchanged. Let me know if this fits your initial request.
Genz
Genz on 15 Oct 2019
its work well. i don't realize there was a "replacement".
many thanks sir. GBU.

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