| der.link | A subfunction used in estimation | 
| fit.simml | Single-index models with multiple-links (workhorse function) | 
| generate.data | A data generation function | 
| ordinal.data | A function for ordinal categorical response data generation. | 
| pred.simml | SIMML prediction function | 
| simml | Single-index models with multiple-links (main function) |