On 2013-04-17, Michael Welsh <yom...@yomcat.geek.nz> wrote: > I have some GF(2) matrices that are incidence matrices of undirected graphs. > When I try to construct the graphs in sage, this happens: > > sage: Graph(matrix(GF(2), [[1,0,1,1],[1,1,0,1],[0,1,1,0]]))
it's not even clear what two parallel edges should lead to. Should they "cancel" each other? > --------------------------------------------------------------------------- > ValueError Traceback (most recent call last) ><ipython-input-1-cf6c24cef566> in <module>() > ----> 1 Graph(matrix(GF(Integer(2)), > [[Integer(1),Integer(0),Integer(1),Integer(1)],[Integer(1),Integer(1),Integer(0),Integer(1)],[Integer(0),Integer(1),Integer(1),Integer(0)]])) > > /Applications/sage/local/lib/python2.7/site-packages/sage/graphs/graph.pyc in > __init__(self, data, pos, loops, format, boundary, weighted, implementation, > sparse, vertex_labels, name, multiedges, convert_empty_dict_labels_to_None) > 1288 multiedges = ( len(uniq(positions)) < total ) > 1289 except AssertionError: > -> 1290 raise ValueError(msg) > 1291 num_verts = data.nrows() > 1292 elif format == 'Graph': > > ValueError: Non-symmetric or non-square matrix assumed to be an incidence > matrix: Each column represents an edge: -1 goes to 1. > sage: > > Is there a way around this, apart from manually changing each column so that > it has a -1 in it? > > Michael > -- 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.
