Mauch MIREX 2010

function M = unroll_dbn_topology(intra, inter, T, intra1)

% UNROLL_DBN_TOPOLOGY Make the block diagonal adjacency matrix for a DBN consisting of T slices

% M = unroll_dbn_topology(intra, inter, T, intra1)

%

% intra is the connectivity within a slice, inter between two slices.

% M will have intra along the diagonal, and inter one above the diagonal.

% intra1 is an optional argumnet, in case the intra is different for the first slice.

if nargin < 4, intra1 = intra; end

ss = length(intra); % slice size

M = sparse(ss*T, ss*T);

b = 1:ss;

M(b,b) = intra1;

M(b,b+ss) = inter;

for t=2:T-1

  b = (1:ss) + (t-1)*ss;

  M(b,b) = intra;

  M(b,b+ss) = inter;

end

t = T;

b = (1:ss) + (t-1)*ss;

M(b,b) = intra;