yamada#
Compute the Yamada polynomial of a knotted planar diagram described in [Yamada, S. (1989). An invariant of spatial graphs. Journal of Graph Theory, 13(5), 537-551].
Optimizations: * precomputed powers of sigma = A + 1 + 1/A, * simplification of the knotted graphs mid-computation (reducing crossings via R1 unkinks and R2 unpokes,…) * caching of the Yamada polynomials for planar graphs, * caching of the Yamada polynomials for knotted graphs.
- yamada(k, normalize=True)#
Return the Yamada polynomial of a given planar diagram.
- Parameters:
k (PlanarDiagram) – Planar diagram (knotted spatial graph allowed).
normalize (bool) – If True, multiply by a power of
(-A)so the lowest term is constant.
- Returns:
SymPy expression for the Yamada polynomial.
- Return type:
Expr