| b_rcs | Basis for restricted cubic splines |
| b_rcs_prime | Derive first derivatives of RCS |
| cs_per | Generate design matrix for periodic cubic splines |
| plot_per_mod | Plotting function for periodic curves model |
| rcs_per | Generate design matrix for periodic restricted cubic spline |
| viral_east_mediteranean | Viral etiology, seasonality and severity of hospitalized patients with severe acute respiratory infections in the Eastern Mediterranean Region, 2007-2014 |