# gaussianParametrization(...,SimpleTreks=>...) -- optional input for gaussianParametrization

## Synopsis

• Usage:
M = gaussianParametrization(R,SimpleTreks => true)
• Inputs:
• R, a ring, which should be a gaussianRing
• Outputs:
• M, , the parametrization of the covariance matrix in terms of treks

## Description

Put SimpleTreks => true as an argument in the function gaussianParametrization to compute a parametrization of the covariance matrix $S=(s_{(i,j)})$ where $s_{(i,j)}$ is the sum of monomials corresponding to simple treks between vertices $i$ and $j$. Here, a simple trek is a trek $(P_L,P_R)$ where the paths $P_L$ and $P_R$ do not have any common vertices except perhaps at their source. See trekSeparation for the definition of a trek.

If the option SimpleTreks => false is used, then the sum is over all treks, and not just simple treks.