Set control parameters for cumulative link models
clm2.control(method = c("ucminf", "Newton", "nlminb", "optim",
            "model.frame"), ..., convTol = 1e-4,
            trace = 0, maxIter = 100, gradTol = 1e-5,
            maxLineIter = 10)the optimizer used to maximize the likelihood
    function. "Newton" only works for models without scale,
    structured thresholds and flexible link functions,
    but is considerably faster than the other
    optimizers when applicable. model.frame simply returns a list
    of model frames with the location, scale and nominal model
    frames. "optim" uses the "BFGS" method.
convergence criterion on the size of the maximum absolute gradient.
numerical, if > 0 information is printed about and during
    the optimization process. Defaults to 0.
the maximum number of Newton-Raphson iterations.
    Defaults to 100.
the maximum absolute gradient. This is the termination
    criterion and defaults to 1e-5.
the maximum number of step halfings allowed if
    a Newton(-Raphson) step over shoots. Defaults to 10.
a list of control parameters.