| avar | Asymptotic variance of Estimator |
| ids_with_multiple_obs | 'ids_with_multiple_obs' returns a vector of values that occur multiple times |
| nonredundant | Nonredundant |
| projdummies | Projection Dummies |
| projvar | Project Variables |
| regress1 | Regression |
| where_id_with_single_obs | 'where_id_with_single_obs' returns a true/false vector, Does this dummy occur multiple times? |
| xtreg2way | Estimation of Two Way Fixed Effects Model |
| xtreg2way.default | Estimation of Two Way Fixed Effects Model |
| xtreg2way.formula | Estimation of Two Way Fixed Effects Model |