# Divide the matrix randomly, based on columns

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Joana on 11 Dec 2019
Commented: Rik on 11 Dec 2019
Hi
I have a matrix x of size 78000x204. I need to divide it into nonoverlapping but random 70:15:15 percent of the data, based on number of columns.
Any help, how to do that.?

Rik on 11 Dec 2019
You mean like this?
fractions=[70 15 15];
x=rand(78000,100);%use 100 to show the split is indeed 75:15:15
groups=cell(size(fractions));%pre-allocate output
f=fractions/sum(fractions);
f=[0 cumsum(f)];
r=randperm(size(x,2))/size(x,2);
for n=1:numel(groups)
L= r>f(n) & r<=f(n+1);
groups{n}=x(:,L);
end
##### 2 CommentsShow 1 older commentHide 1 older comment
Rik on 11 Dec 2019
Because randperm is generating the indices, this is guaranteed not to result in overlapping groups. Unless there are columns in your data that are equal to eachother, there is not be any match between the groups.

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