function a = plantbisection(k, p, q)
% function a = plantbisection(k, p, q)
%
%
% make p inside edge prob, q outside edge prob, p > q

a = sparse(2*k,2*k);

a([1:k],k + [1:k]) = rand(k,k) > (1-q);

a(k + [1:k],k + [1:k]) = rand(k,k) > (1-p);
a([1:k],[1:k]) = rand(k,k) > (1-p);
a = triu(a,1); a = a + a';
