matlab - how to generate bit sequence randomized over 2 bits -

i have network 4 different types of nodes a, b, c , d represented 00, 01, 10 , 11
respectively. want create random sequence of nodes, e.g. a b d c d c b c d (00 01 11 10 00 11 10 01 10 11), such that: no_of_type nodes > no_of_type b nodes > no_of_type c nodes. how can generate such bit sequence using matlab.

use randperm obtain random permuation of ordered sequence of as, bs, cs , ds number of as, bs, cs, ds descending. can achieve drawing random numbers have constant sum (effectively drawing 1 less) , sorting them. in simple approach need retry several times because numbers of as, bs, cs or ds cannot equal according specification.

code example:

% total length of sequence n = 10;  % try again until found list of lengths has no equal entries ni = [0,0]; % long there 2 equal numbers inside while any(diff(ni) == 0)     % 1 length can value     n1 = round(rand()*n);     % remaining     n2 = round(rand()*(n-n1));     % remaining     n3 = round(rand()*(n-n1-n2));     % remaining     n4 = n - n1 - n2 - n3;     % sort     ni = sort([n1, n2, n3, n4]); end  % translate a, b, c, d r = [repmat('a', 1, ni(4)), repmat('b', 1, ni(3)), repmat('c', 1, ni(2)), repmat('d', 1, ni(1))]; r % random permuatation s = r(randperm(length(r))); s 

gives:

aaaaaaabbc aabaabacaa 

where first 1 ordered random sequence (showing indeed number of larger number of bs, ...) , second desired random sequence. translating bits trivial.