Talk:Directed graph
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I feel this page does not contain enough information about the context of its subject. It is not made clear in what scientific or mathematical fields one is likely to encounter a digraph, nor is any information presented about how they are useful. 75.162.233.85 (talk) 05:56, 15 October 2008 (UTC)
[edit] Three pieces of data?
Why is the third of these needed? Seems to me that it is superfluous; a digraph is a set of nodes, and a (multi)set of ordered pairs (arcs) node→node. I guess the nodes need to all be connected too, but that does't follow from the article, which says:
JöG (talk) 12:22, 22 November 2008 (UTC)
- You are right: "two maps" is not part of the mathematical definition. Although they may appear useful in some computer representations of digraphs. Twri (talk) 00:10, 25 November 2008 (UTC)
[edit] defination of directed graphs
Definitions of Directed graph on the Web: • A directed graph or digraph is an ordered pair with * is a set, whose elements are called vertices or nodes, * is a set of ordered pairs of vertices, called directed edges, arcs, or arrows. •
A graph in which the edges are ordered pairs, so that, if the edge (a, b) is in the graph, the edge (b, a) need not be in the graph and is ...
• • A graph with signed edges. For example, in a protein interaction network, we have excitatory interactions (which might be represented by an edge ...
• A graph with one-way edges. See also directed acyclic graph (DAG).
• (digraph):The edges are ordered pairs of V (ie the binary relation is not necessarily symmetric).
• A graph in which information flows between vertices unidirectionally.
• A graph is a directed graph if the edges have a direction, ieif they are arrows with a head and a tail.
(Jabihul Quamar Jugnu & Shailendra Pratap) —Preceding unsigned comment added by 59.180.153.186 (talk) 07:07, 27 April 2009 (UTC)
