insert into array with probability

I have one array a=[...] and confidence array. Confidence array have the same length with a array, and confidence(i) means the probability with wich i should insert element a(i) into array b. How can i generate inserting into b array with probability?

so for example if a(1)=5 and confidence(1)=0.37 it means that i have to insert 5 into array b with probability 0.37

Answer 1

[Teja Muppirala]

% Make some arbitrary a, b, and confidence matrix
a = randi(10,[1 10]);
b = 100*(1:numel(a));
confidence = rand(size(a));

% Replace the elements of b based on the probabilities in "confidence"
pos = (confidence >= rand);
b(pos) = a(pos)

Answer 2

[Oleg Komarov]

% Create sample a and cf
a  = randi([1,100],4,1);
cf = rand(4,1); 
cf = cf/sum(cf);

% Suppose our b has 1000 elements
n = 1000;

% create b
len = round(n*cf);
b   = rude(len,cf); % You can find rude on the fex

% Make sure b has 1000 elements
numB = numel(b);
if numB > n
    b(randi([1 n],1)) = 0;
elseif numB < n
    b = [b a(randi([1 4],1))];
end

% Scatter b
b = b(randperm(n));