This command selects a quadratic-linear objective function. Given this estimator, the objective function to be minimized is a combination of least-squares for small residuals and the first norm for residuals larger than c-times the prior standard deviation:
This objective function does not correspond to a standard probability density function.
It has the general characteristic that the weight given individual residuals first increases
quadratically with deviation, then only linearly to reduce the impact of outliers.
>>> use a QUADRATIC-LINEAR robust estimator with a constant c : 1.0