I am reading the book by Arkani-Hamed et al. I see how one can get the permutation from a plabic graph, and I see how different plabic graphs can be shown to be equivalent through moves. But I don't see how to start from the scattering information (how many particles scatter, and how many have negative helicities, and maybe the Feynman diagram loop order, although I know this last parameter is not central in plabic graphs) to the corresponding plabic graphs. What is the algorithm? (by the way, I do know how to get from a permutation to a graph, using BCFW bridges as on page 68 of the book).
Thanks to anyone who can help.