Mauch MIREX 2010

function [A, names] = mk_adj_mat(connections, names, topological)

% MK_ADJ_MAT Make a directed adjacency matrix from a list of connections between named nodes.

%

% A = mk_adj_mat(connections, name)

% This is best explaine by an example:

%   names = {'WetGrass', 'Sprinkler', 'Cloudy', 'Rain'}; 

%   connections = {'Cloudy', 'Sprinkler'; 'Cloudy', 'Rain'; 'Sprinkler', 'WetGrass'; 'Rain', 'WetGrass'}; 

% adds the arcs C -> S, C -> R, S -> W, R -> W. Node 1 is W, 2 is S, 3 is C, 4 is R.

%

% [A, names] = mk_adj_mat(connections, name, 1)

% The last argument of 1 indicates that we should topologically sort the nodes (parents before children).

% In the example, the numbering becomes: node 1 is C, 2 is R, 3 is S, 4 is W

% and the return value of names gets permuted to {'Cloudy', 'Rain', 'Sprinkler', 'WetGrass'}.

% Note that topological sorting the graph is only possible if it has no directed cycles.

if nargin < 3, topological = 0; end

n=length(names);

A=zeros(n);

[nr nc] = size(connections);

for r=1:nr

  from = strmatch(connections{r,1}, names, 'exact');

  assert(~isempty(from));

  to = strmatch(connections{r,2}, names, 'exact');

  assert(~isempty(to));

  %fprintf(1, 'from %s %d to %s %d\n', connections{r,1}, from, connections{r,2}, to);

  A(from,to) = 1;

end

if topological

  order = topological_sort(A); 

  A = A(order, order); 

  names = names(order); 

end