How I can randomly divide my data

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Sehairi K. 2017-9-25

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https://ww2.mathworks.cn/matlabcentral/answers/358252-how-i-can-randomly-divide-my-data

编辑： Jan 2017-9-26

I have a matrix X with size nxm, How I can choose randomly 70 percent of this data and put it in matrix A and the rest in matrix B. I have already selected the 70% (according to rows) using the 'datasample' function, is there any tip to select the rest 30% of the data with there indices

[n,m]=size(X);
[A,idx] = datasample(X,round(0.7*n));

Thanks in advance for your help

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Answer 1

Jan 2017-9-25

2
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/358252-how-i-can-randomly-divide-my-data#answer_283057

编辑：Jan 2017-9-25

在 MATLAB Online 中打开

[A, idxA]  = datasample(X, round(0.7*n));
idxB       = 1:n;
idxB(idxA) = [];
B          = X(idxB);

This is slightly faster than:

idxB = setdiff(1:n, idxA);

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Sehairi K. 2017-9-25

在 MATLAB Online 中打开

I tride also that

row_idx = randperm(round(0.7*n))';
A_Idx = logical(zeros(size(X,1),1));                 
A_Idx(row_idx) = true;                                  
B_Idx = ~A_Idx; 
A_Data = Data(A_Idx,:);
B_Data = Data(B_Idx,:);
But I think your code is more optimized

Jan 2017-9-26

编辑：Jan 2017-9-26

在 MATLAB Online 中打开

In the 2nd line the vector 1:n is created, and in the third line the indices used to create A are removed, such that you get the indices required for B.

The approach with randperm:

row_idx = randperm(n, round(n * 0.7));  % 2 inputs!
A_idx   = false(n, 1);   % logical(zeros()) wastes time
A       = X(A_idx,  :);
B       = X(~A_idx, :);

I assume that this is faster than with datasample and the index vector.

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