Creates an object for calculating Omega/Omega^-1 and derivatives
rxSymInvCholCreate(mat, diag.xform = c("log", "sqrt", "identity"),
create.env = TRUE, envir = parent.frame())
Initial Omega matrix
transformation to diagonal elements of OMEGA. or chol(Omega^-1)
-- Create an environment to calculate the inverses. (By default TRUE)
-- Environment to evaluate function, bu default it is the parent frame.
A rxSymInv object OR a rxSymInv environment