The graphic ideal associated to a polytope is the toric ideal of the vector configuration consisting of the columns of the vertex-edge incidence matrix of the non-incidence (of vertices and facets) graph of the polytope.
i1 : P = convexHull(matrix{{0, 0, 1, 1}, {0, 1, 0, 1}}); |
i2 : T = graphicIdeal P Order of vertices is {{0, 0}, {1, 0}, {0, 1}, {1, 1}} Graph computed from symbolic adjacency matrix: | 0 y_1 0 y_2 | | y_3 0 0 y_4 | | 0 y_5 y_6 0 | | y_7 0 y_8 0 | o2 = ideal(y y y y - y y y y ) 0 3 5 6 1 2 4 7 o2 : Ideal of QQ[y ..y ] 0 7 |
If S is not a symbolic slack matrix, the ideal will have variables indexed as in symbolicSlackMatrix (from left to right in order by rows of S).
The object graphicIdeal is a method function with options.