| HCinitial | Two-Step Method for Parameter Estimation of the Heckman Model | 
| HeckmanBS | Heckman BS Model fit Function | 
| HeckmanCL | Classic Heckman Model fit Function | 
| HeckmanGe | Function for fit of the Generalized Heckman Model | 
| HeckmanSK | Normal Skew Model fit Function | 
| HeckmantS | Heckman-t Model fit Function | 
| IMR | Inverse Mills Ratio | 
| MEPS2001 | Medical Expenditure Panel Survey | 
| Mroz87 | U.S. Women's Labor Force Participation | 
| nhanes | US National Health and Nutrition Examination Study | 
| PSID2 | Panel Study of Income Dynamics | 
| RandHIE | RAND Health Insurance Experiment | 
| ssmodels | ssmodels: A package for fit the sample selection models. | 
| step2 | Heckman's two-step method | 
| summary.HeckmanBS | Summary of Birnbaum-Saunders Heckman Model | 
| summary.HeckmanCL | Summary of Classic Heckman Model | 
| summary.HeckmanGe | Summary of Generalized Heckman Model | 
| summary.HeckmanSK | Summary of Skew-Normal Heckman Model | 
| summary.HeckmantS | Summary of Heckman-ts Model | 
| twostep | Heckman's two-step method |