Hello (maybe, I should have written Helloooooooooooo Nathann :-) ), I want to plot a planar graph and I know (from graph theory) that the graph can be plotted in various ways.
I have in mind one algorithm to draw planar graphs, removing one cycle and forking to draw planar sub-graphs either inside or outside the cycle. When I am using the default (string) layout, I am not fully satisfied because graph plot is always changing and I am lucky if the plot is without edges intersections. When I am using the "planar" (Schnyder woods) layout, the plot is planar with no edges intersecting....good...and satisfying the sagemath doc...but some faces are plotted "reversed" : for example if I have a triangular face ABC (reading vertices names clockwise in my dreamed plot), sometimes I got ACB. Is it a flaw or have I misunderstood what is "triangles oriented correctly" in https://www.ics.uci.edu/~eppstein/gina/schnyder/ ? How is defined the "orientation" in sagemath graph module ? Next is example of graph from the geometry about how to cut an obtuse triangle ACB into seven acute isosceles triangles : graph has seven faces (except the infinite area one) and I would like to get a planar plot with orientation for triangular faces : AID, DIF, BDF, AEI, EGI, GFI, CGE Dominique # Draw example planar graph for vertices : split obtuse triangle into seven triangles Graph_1 = Graph({'A':['D','E','I'],'B':['F','D'],'C':['E','G'],'D':['A','B','F','I'],'E':['A','C','G','I'],'F':['B','D','G','I'],'G':['C','E','F','I'],'I':['A','D','E','F','G']},sparse=True) Graph_1.show(vertex_size=1000,vertex_shape="h") pos_dict = Graph_1.layout(layout="planar", save_pos=True); pos_dict pl = Graph_1.plot(pos=pos_dict,vertex_size=1000,vertex_shape="h",graph_border=True) pl.show(axes=True,aspect_ratio=True) -- 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. For more options, visit https://groups.google.com/d/optout.
