matthiasm@8: function H = entropy(v, scale)
matthiasm@8: % ENTROPY Entropy log base 2
matthiasm@8: % H = entropy(v)
matthiasm@8: % If v is a matrix, we compute the entropy of each column
matthiasm@8: %
matthiasm@8: % % H = entropy(v,1) means we scale the result so that it lies in [0,1]
matthiasm@8: 
matthiasm@8: if nargin < 2, scale = 0; end
matthiasm@8: 
matthiasm@8: v = v + (v==0);
matthiasm@8: H = -1 * sum(v .* log2(v), 1); % sum the rows
matthiasm@8: 
matthiasm@8: if scale
matthiasm@8:   n = size(v, 1);
matthiasm@8:   unif = normalise(ones(n,1));
matthiasm@8:   H = H / entropy(unif);
matthiasm@8: end