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--- tutorial:apps_graph [2009/11/03 13:00] – created sherrmann
+++ user_guide:apps_graph [2019/01/25 09:27] – ↷ Page moved from tutorial:apps_graph to user_guide:apps_graph oroehrig
@@ Line 150: / Line 150: @@
 </code>
+===== Directed Graphs =====
+By specifying the template parameter ''Directed'' a graph is born as a directed graph.  Properties which make sense for directed graphs work as expected.  A directed graph may have two arcs between any two nodes with opposite orientations.
+<code>
+graph > $g=new objects::Graph<Directed>(ADJACENCY=>[[1],[2],[3],[2,4],[0]]);
+graph > print $g->DIAMETER;
+</code>
+Here is an example of an undirected graph property which does not make sense for directed graphs.
+<code>
+graph > #print $g->MAX_CLIQUES;
+polymake:  ERROR: Object Graph<Directed> does not have a property or method MAX_CLIQUES
+</code>
+Graphs with multiple edges/arcs are currently not supported.
+===== Visualizing Graphs =====
+Like other "big" ''polymake'' objects the ''Graph'' class has a member (function) ''VISUAL'' which returns an abstract visualization object.  Depending on the configuration it typically uses ''JReality'' or ''JavaView''.  Particularly interesting for graph drawing is the visualization via ''Graphviz''.
+<code>
+graph > graphviz($g->VISUAL);
+</code>
+Note that the latter starts a postscript viewer with the ''Graphviz'' output.  Make sure that the custom variable ''$Postscript::viewer'' is set to something reasonable (like, e.g., ''/usr/bin/evince'').