%% New features in MatlabBGL version 4.0
% MatlabBGL 3.0 was only released as a beta test. Version 4.0 is a
% full release with quite a few new features.
%% Improved reweighted graphs
% In MatlabBGL 3.0, reweighted graphs were a pain to use. Now they are
% simple! We combine a structural matrix with a weight matrix. As(i,j)=1
% if there is an edge between vertex i and j and A(i,j)=wij where wij is
% the weight of the edge between i and j.
As = cycle_graph(6,'directed',0); % compute a 6 node cycle graph
A = As; % set all the weights to be one initially
A(2,3) = 0; A(3,2) = 0; % make one edge have zero weight
fprintf('Edges\n');
full(As)
fprintf('Weights\n');
full(A)
%%
% Note that As is given as the graph in the following call, not A!
[d pred] = shortest_paths(As,1,'edge_weight',edge_weight_vector(As,A));
d(3) % distance from vertex 1 to vertex 3 should be just 1!
%% Graph layout algorithms
% Sometimes, it's really nice to see a picture of your graph. The BGL
% implements a few graph layout algorithms and so these are now in
% MatlabBGL 4.0!
%%
G = grid_graph(6,5);
X = kamada_kawai_spring_layout(G);
gplot(G,X,'.-');
%%
G = grid_graph(6,5);
X = fruchterman_reingold_force_directed_layout(G);
gplot(G,X,'.-');
%%
G = grid_graph(6,5);
X = gursoy_atun_layout(G);
gplot(G,X,'.-');
%% Planar graph algorithms
% The Boost Graph Library received a new suite of planar graph algorithms.
% These are now in MatlabBGL too.
%%
% A grid in the xy plane is a planar graph.
G = grid_graph(6,5);
is_planar = boyer_myrvold_planarity_test(G)
%%
% Recall that K_5 (the clique on 5 vertices) is not a planar graph. Let's
% see what happens.
K5 = clique_graph(5);
is_planar = test_planar_graph(K5) % helpful wrapper
%%
% We can also draw planar graphs
G = grid_graph(6,5);
X = chrobak_payne_straight_line_drawing(G);
gplot(G,X,'.-'); % it looks a little different!
%% New option syntax
% You probably noticed that the "struct" command that permeated MatlabBGL
% calls before is gone in these examples. We've moved to a new option
% syntax that gives you the _choice_ between the MatlabBGL struct style
% arguments and a list of key-value pairs
%%
% We'll look at spanning trees on the clique graph with 5 vertices.
% Using Prim's algorithm, the spanning tree we get depends on the root. We
% always get a star graph rooted at the vertex we pick as the root.
G = clique_graph(5);
%%
% Old style
full(mst(G,struct('root',5,'algname','prim')))
%%
% New style
%%
% Just to make sure it works
full(mst(G,'root',1,'algname','prim'))