Covariance-Based Ellipses and Annotation Tools for Ordination Plots R package barrel version 0.1.0 Provides tools to visualize ordination results in 'R' by adding covariance-based ellipses, centroids, vectors, and confidence regions to plots created with 'ggplot2'. The package extends the 'vegan' framework and supports Principal Component Analysis (PCA), Redundancy Analysis (RDA), and Non-metric Multidimensional Scaling (NMDS). Ellipses can represent either group dispersion (standard deviation, SD) or centroid precision (standard error, SE), following Wang et al. (2015) <doi:10.1371/journal.pone.0118537>. Robust estimators of covariance are implemented, including the Minimum Covariance Determinant (MCD) method of Hubert et al. (2018) <doi:10.1002/wics.1421>. This approach reduces the influence of outliers. barrel is particularly useful for multivariate ecological datasets, promoting reproducible, publication-quality ordination graphics with minimal effort. Software Imports: robustbase, ggplot2, stats, ggrepel, vegan, grid, rlang Suggests: knitr, rmarkdown, testthat (>= 3.0.0), vdiffr Diego Barranco-Elena <diego.barranco@udl.cat> Comprehensive R Archive Network (CRAN) Diego Barranco-Elena [aut, cre] MIT + file LICENSE (https://CRAN.R-project.org/package=barrel/LICENSE) 2025-11-03 application/tgz https://CRAN.R-project.org/package=barrel doi:10.32614/CRAN.package.barrel en-US