GROPPOSITENODE Return opposite node in an edge.

   NODE2 = grOppositeNode(EDGE, NODE);
   Return the index of the node opposite to NODE in EDGE.
   If the edge does not contain node NODE, result is 0.

   Works also if EDGE is a N-by-2 array of source and target vertex
   indices, in this case the result NODE2 has as many rows as the number
   of edges.

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 Author: David Legland
 e-mail: david.legland@grignon.inra.fr
 Created: 2010-09-07
 Copyright 2006 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas).

Package: matgeom