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<html xmlns:mwsh="http://www.mathworks.com/namespace/mcode/v1/syntaxhighlight.dtd"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <!--This HTML is auto-generated from an M-file.To make changes, update the M-file and republish this document. --> <title>New features in MatlabBGL version 4.0</title> <meta name="generator" content="MATLAB 7.5"> <meta name="date" content="2008-10-22"> <meta name="m-file" content="new_in_4_0"> <link rel="stylesheet" type="text/css" href="../site.css"><style>body { background: white; color: black;}p.footer { text-align: right; font-size: xx-small; font-weight: lighter; font-style: italic; color: gray;}pre.codeinput { margin-left: 20px; margin-top: 10px; margin-bottom: 10px; background-color: #bbbbbb; border: solid 1px; font-size: 10pt; width: 620px;}p{ margin: 10px;}hr{ color: #bbbbbb; height: 4;}.main{ border-left-style: solid; margin-left: 100px; width: 650px;}.upwhitesq{ position: relative; left: -5px; top: -8px; background: white; }.downwhitesq{ position: relative; left: 95px; bottom: 10px; background: white; }img{ text-align: center;}span.keyword {color: #0000FF}span.comment {color: #228B22}span.string {color: #A020F0}span.untermstring {color: #B20000}span.syscmd {color: #B28C00}pre.showbuttons { margin-left: 30px; border: solid black 2px; padding: 4px; background: #EBEFF3;}pre.codeoutput { margin-left: 20px; margin-top: 10px; margin-bottom: 10px; font-size: 10pt; width: 520px;}pre.error { color: red;}.intro { width: 650px;} </style></head> <body> <h1>New features in MatlabBGL version 4.0</h1> <introduction> <div class="intro"> <p>MatlabBGL 3.0 was only released as a beta test. Version 4.0 is a full release with quite a few new features.</p> </div> </introduction> <h2>Contents</h2> <div> <ul> <li><a href="#1">Improved reweighted graphs</a></li> <li><a href="#3">Graph layout algorithms</a></li> <li><a href="#7">Planar graph algorithms</a></li> <li><a href="#11">New option syntax</a></li> </ul> </div> <div class="main"> <h2>Improved reweighted graphs<a name="1"></a></h2> <p>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. </p><pre class="codeinput">As = cycle_graph(6,<span class="string">'directed'</span>,0); <span class="comment">% compute a 6 node cycle graph</span>A = As; <span class="comment">% set all the weights to be one initially</span>A(2,3) = 0; A(3,2) = 0; <span class="comment">% make one edge have zero weight</span>fprintf(<span class="string">'Edges\n'</span>);full(As)fprintf(<span class="string">'Weights\n'</span>);full(A)</pre><pre class="codeoutput">Edgesans = 0 1 0 0 0 1 1 0 1 0 0 0 0 1 0 1 0 0 0 0 1 0 1 0 0 0 0 1 0 1 1 0 0 0 1 0Weightsans = 0 1 0 0 0 1 1 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 1 0 0 0 0 1 0 1 1 0 0 0 1 0</pre><p>Note that As is given as the graph in the following call, not A!</p><pre class="codeinput">[d pred] = shortest_paths(As,1,<span class="string">'edge_weight'</span>,edge_weight_vector(As,A));d(3) <span class="comment">% distance from vertex 1 to vertex 3 should be just 1!</span></pre><pre class="codeoutput">ans = 1</pre><hr> <div class="upwhitesq"> </div> <h2>Graph layout algorithms<a name="3"></a></h2> <p>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! </p><pre class="codeinput">G = grid_graph(6,5);X = kamada_kawai_spring_layout(G);gplot(G,X,<span class="string">'.-'</span>);</pre><img vspace="5" hspace="5" src="new_in_4_0_01.png"> <pre class="codeinput">G = grid_graph(6,5);X = fruchterman_reingold_force_directed_layout(G);gplot(G,X,<span class="string">'.-'</span>);</pre><img vspace="5" hspace="5" src="new_in_4_0_02.png"> <pre class="codeinput">G = grid_graph(6,5);X = gursoy_atun_layout(G);gplot(G,X,<span class="string">'.-'</span>);</pre><img vspace="5" hspace="5" src="new_in_4_0_03.png"> <hr> <div class="upwhitesq"> </div> <h2>Planar graph algorithms<a name="7"></a></h2> <p>The Boost Graph Library received a new suite of planar graph algorithms. These are now in MatlabBGL too.</p> <p>A grid in the xy plane is a planar graph.</p><pre class="codeinput">G = grid_graph(6,5);is_planar = boyer_myrvold_planarity_test(G)</pre><pre class="codeoutput">is_planar = 1</pre><p>Recall that K_5 (the clique on 5 vertices) is not a planar graph. Let's see what happens.</p><pre class="codeinput">K5 = clique_graph(5);is_planar = test_planar_graph(K5) <span class="comment">% helpful wrapper</span></pre><pre class="codeoutput">is_planar = 0</pre><p>We can also draw planar graphs</p><pre class="codeinput">G = grid_graph(6,5);X = chrobak_payne_straight_line_drawing(G);gplot(G,X,<span class="string">'.-'</span>); <span class="comment">% it looks a little different!</span></pre><img vspace="5" hspace="5" src="new_in_4_0_04.png"> <hr> <div class="upwhitesq"> </div> <h2>New option syntax<a name="11"></a></h2> <p>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 </p> <p>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. </p><pre class="codeinput">G = clique_graph(5);</pre><p>Old style</p><pre class="codeinput">full(mst(G,struct(<span class="string">'root'</span>,5,<span class="string">'algname'</span>,<span class="string">'prim'</span>)))</pre><pre class="codeoutput">ans = 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 1 1 1 1 0</pre><p>New style</p> <p>Just to make sure it works</p><pre class="codeinput">full(mst(G,<span class="string">'root'</span>,1,<span class="string">'algname'</span>,<span class="string">'prim'</span>))</pre><pre class="codeoutput">ans = 0 1 1 1 1 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0</pre><hr> <div class="upwhitesq"> </div> </div> <div class="downwhitesq"> </div> <!--##### SOURCE BEGIN #####%% 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 graphA = As; % set all the weights to be one initiallyA(2,3) = 0; A(3,2) = 0; % make one edge have zero weightfprintf('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 graphsG = 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 stylefull(mst(G,struct('root',5,'algname','prim')))%%% New style%%% Just to make sure it worksfull(mst(G,'root',1,'algname','prim'))##### SOURCE END #####--> </body></html>⌨️ 快捷键说明
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