| fit_rcpp | Predict y from X and b | 
| mad_rcpp | Median Absolute Deviation (MAD) | 
| median_rcpp | Median | 
| psiBS_rcpp | Tukey's Bisquare Psi Function | 
| psiHuber_rcpp | Huber Psi Function | 
| robustRegBS | Robust Fitting of Linear Models using Bisquare Psi Function | 
| robustRegH | Robust Fitting of Linear Models using Huber Psi Function |