That might not have been terribly clear -- the point is, "incidence" of edges and vertices is a binary relation. One needs to make a choice to orient the matrix to make the linear algebra coincidence work out.
On Mon, Apr 22, 2013 at 8:51 AM, Tom Boothby <tomas.boot...@gmail.com> wrote: >> Yes it does, in a way. If you want to construct the Laplacian matrix L of the >> graph from the incidence matrix E just by using matrix multiplication, >> you need to pick up an orientation for each edge, i.e. assigning +1 to >> one end, and -1 to the other. Then, bingo, you have L=E.T*E > > I've always seen that described as: "take a random orientation of an > incidence matrix and multiply it by its transpose to get the > Laplacian". -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
