Question

How can I create in Matlab a matrix (100 x 100) with random distribution of numbers 1 and 3, when in each column I must have 10% of numbers 1 and 90% of numbers 3? this must be random distribution.

Anyone could help me?

Thanks a ton!

Answer 1

v = [1*ones(10,1) ; 3*ones(90,1)];
A = zeros(100,100);
for i = 1:100,
   A(:,i) = v(randperm(100));
end

or without a for loop

A = zeros(100,100);
v = [1*ones(10*100,1) ; 3*ones(90*100,1)];
A(:) = v(randperm(100*100));

Though the first one might be better if you want to explicitly control the columns differently later.

Edit: Actually, one subtle point. The first piece of code guarantees each column to have exactly 10 1’s and exactly 90 3’s. the second piece of code doen’t make this guarantee, only that the entire matrix has 1000 1’s and 9000 3’s.