gaussianRing(...,pVariableName=>...) -- symbol used for indeterminates in a ring of Gaussian joint probability distributions

i1 : G = mixedGraph(digraph {{b,{c,d}},{c,{d}}},bigraph {{a,d}})

o1 = MixedGraph{Bigraph => Bigraph{a => {d}}   }
                                   d => {a}
                Digraph => Digraph{b => {c, d}}
                                   c => {d}
                                   d => {}
                Graph => Graph{}

o1 : MixedGraph

i2 : R = gaussianRing G

o2 = R

o2 : PolynomialRing

i3 : gens R

o3 = {l   , l   , l   , p   , p   , p   , p   , p   , s   , s   , s   , s   , s   , s   , s   , s   , s   , s   }
       b,c   b,d   c,d   a,a   b,b   c,c   d,d   a,d   a,a   a,b   a,c   a,d   b,b   b,c   b,d   c,c   c,d   d,d

o3 : List

i4 : R = gaussianRing (G,pVariableName => psi)

o4 = R

o4 : PolynomialRing

i5 : gens R

o5 = {l   , l   , l   , psi   , psi   , psi   , psi   , psi   , s   , s   , s   , s   , s   , s   , s   , s   , s   , s   }
       b,c   b,d   c,d     a,a     b,b     c,c     d,d     a,d   a,a   a,b   a,c   a,d   b,b   b,c   b,d   c,c   c,d   d,d

o5 : List