Daniel@0: function [A, names] = mk_adj_mat(connections, names, topological)
Daniel@0: % MK_ADJ_MAT Make a directed adjacency matrix from a list of connections between named nodes.
Daniel@0: %
Daniel@0: % A = mk_adj_mat(connections, name)
Daniel@0: % This is best explaine by an example:
Daniel@0: %   names = {'WetGrass', 'Sprinkler', 'Cloudy', 'Rain'}; 
Daniel@0: %   connections = {'Cloudy', 'Sprinkler'; 'Cloudy', 'Rain'; 'Sprinkler', 'WetGrass'; 'Rain', 'WetGrass'}; 
Daniel@0: % adds the arcs C -> S, C -> R, S -> W, R -> W. Node 1 is W, 2 is S, 3 is C, 4 is R.
Daniel@0: %
Daniel@0: % [A, names] = mk_adj_mat(connections, name, 1)
Daniel@0: % The last argument of 1 indicates that we should topologically sort the nodes (parents before children).
Daniel@0: % In the example, the numbering becomes: node 1 is C, 2 is R, 3 is S, 4 is W
Daniel@0: % and the return value of names gets permuted to {'Cloudy', 'Rain', 'Sprinkler', 'WetGrass'}.
Daniel@0: % Note that topological sorting the graph is only possible if it has no directed cycles.
Daniel@0: 
Daniel@0: if nargin < 3, topological = 0; end
Daniel@0:   
Daniel@0: n=length(names);
Daniel@0: A=zeros(n);
Daniel@0: [nr nc] = size(connections);
Daniel@0: for r=1:nr
Daniel@0:   from = strmatch(connections{r,1}, names, 'exact');
Daniel@0:   assert(~isempty(from));
Daniel@0:   to = strmatch(connections{r,2}, names, 'exact');
Daniel@0:   assert(~isempty(to));
Daniel@0:   %fprintf(1, 'from %s %d to %s %d\n', connections{r,1}, from, connections{r,2}, to);
Daniel@0:   A(from,to) = 1;
Daniel@0: end
Daniel@0: 
Daniel@0: if topological
Daniel@0:   order = topological_sort(A); 
Daniel@0:   A = A(order, order); 
Daniel@0:   names = names(order); 
Daniel@0: end
Daniel@0: 
Daniel@0: