Daniel@0: function [ll, p] = prob_path(prior, transmat, obsmat, qs)
Daniel@0: % PROB_PATH Compute the prob. of a specific path (state sequence) through an HMM.
Daniel@0: % [ll, p] = prob_path(prior, transmat, obsmat, states)
Daniel@0: %
Daniel@0: % ll = log prob path
Daniel@0: % p(t) = Pr(O(t)) * Pr(Q(t) -> Q(t+1)) for 1<=t<T, p(T) = Pr(O(T))
Daniel@0: 
Daniel@0: T = size(obsmat, 2);
Daniel@0: p = zeros(1,T);
Daniel@0: p(1) = prior(qs(1)) * obsmat(qs(1),1);
Daniel@0: for t=2:T
Daniel@0:   p(t) = transmat(qs(t-1), qs(t)) * obsmat(qs(t),t);
Daniel@0: end
Daniel@0: 
Daniel@0: ll = sum(log(p));