function out = RandDir(N)
% Generate a random vector from the set {+/- e_1, +/- e_2,..., +/- e_N}
% where e_i is the ith basis vector. N should be an integer.
I = round(ceil(2*N*rand));
if rem(I,2) == 1
sgn = -1;
else
sgn = 1;
end
out = zeros(N,1);
out(ceil(I/2)) = sgn*1;
end