On Sat, Feb 27, 2010 at 2:54 PM, Jason Grout <jason-s...@creativetrax.com> wrote: > On 02/27/2010 01:41 PM, Rob Beezer wrote: >> >> On Feb 27, 6:37 am, David Joyner<wdjoy...@gmail.com> wrote: >>> >>> There are several places where bipartite graphs >>> differ (at least in the literature) from regular graphs. >>> For example, usually the bipartite graph's adjacency matrix >>> is not square. >> >> I think an "adjacency matrix" should always be square. But for a >> bipartite graph if you order the vertices consecutively within the two >> parts of the bipartition, then you get a block matrix with zero >> matrices in the northwest and southeast corners. And the other two >> corners are transposes of each other (but not square when the >> bipartite sets are different sizes). >> >> This is in the BipartiteGraph class as "reduced_adjacency_matrix()." >> I can't recall ever seeing this matrix given a name, so I don't know >> if this is how one would expect to find it. In the research for your >> graph theory book have you learned what others call it?
Some also call it the transfer matrix, but I don't know if that is standard. > > > There was some discussion several years ago about what this should be > called. I believe this term came from Richard Brualdi's combinatorial > matrix theory book (I remember running down the hall to my advisor's office > to look it up! :), but my memory may be inaccurate. This is correct. It is defined that way on page 107 of Brualdi-Ryser, Combinatorial Matrix Theory. The literature I am referring to is that of coding theorists who work with graphs, but maybe they are using non-standard terms. > > Thanks, > > Jason > > > -- > To post to this group, send an email to sage-devel@googlegroups.com > To unsubscribe from this group, send an email to > sage-devel+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/sage-devel > URL: http://www.sagemath.org > -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
