Semiparametric Transformation Models R package transmdl version 0.1.0 To make the semiparametric transformation models easier to apply in real studies, we introduce this R package, in which the MLE in transformation models via an EM algorithm proposed by Zeng D, Lin DY(2007) <doi:10.1111/j.1369-7412.2007.00606.x> and adaptive lasso method in transformation models proposed by Liu XX, Zeng D(2013) <doi:10.1093/biomet/ast029> are implemented. C++ functions are used to compute complex loops. The coefficient vector and cumulative baseline hazard function can be estimated, along with the corresponding standard errors and P values. Software Imports: graphics, Rcpp, statmod, stats, survival LinkingTo: Rcpp, RcppEigen Suggests: MASS Fengyu Wen <Wenfy1207@qq.com> Comprehensive R Archive Network (CRAN) Fengyu Wen [aut, cre], Baosheng Liang [aut] GPL (>= 2) 2021-10-14 application/tgz https://CRAN.R-project.org/package=transmdl doi:10.32614/CRAN.package.transmdl