rzi(n, x, z, a, b, theta=1, family=c("poisson", "negbin", "geometric"), infl=TRUE)x, length must be the same as column size of xz, length must be the same as column size of zfamily="negbin"Zhu Wang, Shuangge Ma and Ching-Yun Wang (2015) Variable selection for zero-inflated and overdispersed data with application to health care demand in Germany, Biometrical Journal. 57(5):867-84.