randomly divide vector into 2 parts.

Asked by RUCHI CHOUDHARY on 15 Sep 2019

Latest activity Edited by Bruno Luong on 15 Sep 2019

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i have vector 100000*1 .i want to randomly divide data of it into 80% and 20% and store them into 2 vector.Divide of data must be random.

"non_zero_entry" is total how many entry in the vector.i tried to do this but it show me error "Index exceeds the number of array elements (80000)".

training_data=.8;
tf = false(length(non_zero_entry),1);
tf(1:round(training_data*non_zero_entry)) = true;
tf = tf(randperm(non_zero_entry));  % error occur in this line "Index exceeds the number of array elements (80000)". 
dataTraining = index_rating(tf,:); 
dataTesting = index_rating(~tf,:);

Thanks in advance for your help.

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Answer by Rik on 15 Sep 2019

Accepted Answer

I don't fully understand every step of your code, so I rewrote it:

index_rating=rand(100000,5);%generate example data
training_data=.8;
s=rand(size(index_rating,1),1);
sorted=sort(s);
cutoff=sorted(round(training_data*numel(s)));
tf=s<=cutoff;
dataTraining = index_rating(tf,:); 
dataTesting = index_rating(~tf,:);

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Answer by Bruno Luong on 15 Sep 2019

Edited by Bruno Luong on 15 Sep 2019

For the record, here is how I would do:

n = size(index_rating,1);
i = randperm(n,round(training_data*n));
dataTraining = index_rating(i,:); 
dataTesting  = index_rating(setdiff(1:n,i),:);

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Answer by Bruno Luong on 15 Sep 2019

Edited by Bruno Luong on 15 Sep 2019

Always post complete code that can run. don't less us geuss what is the size/class of the inputs

First assumption: non_zero_entry is a integer scalar, then change the allocation to

tf = false(non_zero_entry,1);

Second assumption non_zero_entry is a vector then change

tf = tf(randperm(non_zero_entry));

tf = tf(randperm(end))

Similarly correction must be applied for the earlier instruction

tf(1:round(training_data*end)) = true

You are now following this question

RUCHI CHOUDHARY (view profile)