| PanelCount-package | Random Effects and Sample Selection Models for Panel Counting Data |
| CRE | A Model with Correlated Random Effects in Poisson and Probit Equations |
| CRE_SS | A Sample Selection Model with Correlated Random Effects |
| PanelCount | Random Effects and Sample Selection Models for Panel Counting Data |
| PLN_RE | A Poisson Lognormal Model with Random Effects |
| PoissonRE | A Poisson Model with Random Effects |
| ProbitRE | A Probit Model with Random Effects |
| rt | Number of words in quoted retweets |