# Randomising a vector with respect to the probability of the outcome

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Marek Galus on 13 Oct 2021
Commented: Marek Galus on 14 Oct 2021
Hi, I have 60 trials which have two outcomes 0 and 1 with probabilities of 80% and 20%.
I want to randomise this 60x1 matrix in such a way that every 5 iterations, outcome 0 occurs 4 times and outcome 1 occurs once as they should.
I tried using ransrc but the 5x1 matrices that I get as an outcome very rarely match the desired probabilites.
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Marek Galus on 14 Oct 2021
Thanks

Mohammad Alhashash on 13 Oct 2021
You can use the randperm function to build 12 basic 5-by-1 matrices and then map the values into 0 and 1 based one your probabilities.
Here what do I mean:
A = [];
m = 60; %length of the main matrix A
for i=1:5:m
a = randperm(5)';
a(a~=1) = 0; % this based on your probability, I used 20% 1 and 80% 0
A = [A;a];
end
Marek Galus on 14 Oct 2021
Thank you!

Matt J on 13 Oct 2021
Edited: Matt J on 13 Oct 2021
I=randi(5,1,12);
J=1:12;
result=reshape( sparse(I,J,1,5,12) ,[],1);
full(result(:))
ans = 60×1
0 0 1 0 0 1 0 0 0 0