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1 function [A, names] = mk_adj_mat(connections, names, topological)
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2 % MK_ADJ_MAT Make a directed adjacency matrix from a list of connections between named nodes.
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3 %
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4 % A = mk_adj_mat(connections, name)
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5 % This is best explaine by an example:
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6 % names = {'WetGrass', 'Sprinkler', 'Cloudy', 'Rain'};
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7 % connections = {'Cloudy', 'Sprinkler'; 'Cloudy', 'Rain'; 'Sprinkler', 'WetGrass'; 'Rain', 'WetGrass'};
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8 % adds the arcs C -> S, C -> R, S -> W, R -> W. Node 1 is W, 2 is S, 3 is C, 4 is R.
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9 %
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10 % [A, names] = mk_adj_mat(connections, name, 1)
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11 % The last argument of 1 indicates that we should topologically sort the nodes (parents before children).
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12 % In the example, the numbering becomes: node 1 is C, 2 is R, 3 is S, 4 is W
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13 % and the return value of names gets permuted to {'Cloudy', 'Rain', 'Sprinkler', 'WetGrass'}.
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14 % Note that topological sorting the graph is only possible if it has no directed cycles.
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15
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16 if nargin < 3, topological = 0; end
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17
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18 n=length(names);
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19 A=zeros(n);
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20 [nr nc] = size(connections);
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21 for r=1:nr
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22 from = strmatch(connections{r,1}, names, 'exact');
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23 assert(~isempty(from));
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24 to = strmatch(connections{r,2}, names, 'exact');
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25 assert(~isempty(to));
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26 %fprintf(1, 'from %s %d to %s %d\n', connections{r,1}, from, connections{r,2}, to);
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27 A(from,to) = 1;
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28 end
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29
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30 if topological
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31 order = topological_sort(A);
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32 A = A(order, order);
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33 names = names(order);
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34 end
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35
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36
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