wolffd@0: function M = unroll_dbn_topology(intra, inter, T, intra1)
wolffd@0: % UNROLL_DBN_TOPOLOGY Make the block diagonal adjacency matrix for a DBN consisting of T slices
wolffd@0: % M = unroll_dbn_topology(intra, inter, T, intra1)
wolffd@0: %
wolffd@0: % intra is the connectivity within a slice, inter between two slices.
wolffd@0: % M will have intra along the diagonal, and inter one above the diagonal.
wolffd@0: % intra1 is an optional argumnet, in case the intra is different for the first slice.
wolffd@0: 
wolffd@0: if nargin < 4, intra1 = intra; end
wolffd@0: 
wolffd@0: ss = length(intra); % slice size
wolffd@0: M = sparse(ss*T, ss*T);
wolffd@0: 
wolffd@0: b = 1:ss;
wolffd@0: M(b,b) = intra1;
wolffd@0: M(b,b+ss) = inter;
wolffd@0: 
wolffd@0: for t=2:T-1
wolffd@0:   b = (1:ss) + (t-1)*ss;
wolffd@0:   M(b,b) = intra;
wolffd@0:   M(b,b+ss) = inter;
wolffd@0: end
wolffd@0: 
wolffd@0: t = T;
wolffd@0: b = (1:ss) + (t-1)*ss;
wolffd@0: M(b,b) = intra;
wolffd@0: 
wolffd@0: