defining function for graph (help needed)
I need help defining a function that does the following (I'm very new to Python/Sage).
I need a function called ihara(G) where G is any graph input by the user.
I need the function ihara(G) to return the Z resulting from all the calculations below:
D = G.to_directed() L = D.line_graph() L.delete_edges([((x,y,None), (y,x,None)) for x,y in G.edges( labels=None)]) L.delete_edges([((x,y,None), (y,x,None)) for y,x in G.edges( labels=None)]) IM = identity_matrix(QQ,D.size()) T = L.adjacency.matrix() var('u') X = IM-u*T Z = X.det()
Could anybody help me with this? or at least get me started in the right direction...