Analysis of Elliptical Tubes Under the Relative Curvature Condition R package ETRep version 1.2.1 Analysis of elliptical tubes with applications in biological modeling. The package is based on the references: Taheri, M., Pizer, S. M., & Schulz, J. (2024) "The Mean Shape under the Relative Curvature Condition." Journal of Computational and Graphical Statistics <doi:10.1080/10618600.2025.2535600> and arXiv <doi:10.48550/arXiv.2404.01043>. Mohsen Taheri Shalmani (2024) "Shape Statistics via Skeletal Structures", PhD Thesis, University of Stavanger, Norway <doi:10.13140/RG.2.2.34500.23685>. Key features include constructing discrete elliptical tubes, calculating transformations, validating structures under the Relative Curvature Condition (RCC), computing means, and generating simulations. Supports intrinsic and non-intrinsic mean calculations and transformations, size estimation, plotting, and random sample generation based on a reference tube. The intrinsic approach relies on the interior path of the original non-convex space, incorporating the RCC, while the non-intrinsic approach uses a basic robotic arm transformation that disregards the RCC. Software Depends: R (>= 4.0.0) Imports: rgl, shapes, Morpho, matlib, RSpincalc, rotations, Rvcg, fields, truncnorm, htmlwidgets Mohsen Taheri Shalmani <MohsenTaheriShalmani@gmail.com> Comprehensive R Archive Network (CRAN) Mohsen Taheri Shalmani [aut, cre] (ORCID: <https://orcid.org/0000-0003-4044-8507>), Jörn Schulz [aut], Stephen M. Pizer [aut] MIT + file LICENSE (https://CRAN.R-project.org/package=ETRep/LICENSE) 2025-09-27 application/tgz https://CRAN.R-project.org/package=ETRep doi:10.32614/CRAN.package.ETRep