Goodness-of-Fit Tests and Diagrams Based on Mellin Log-Cumulants R package logcumulant version 0.1.0 A family of three complementary goodness-of-fit tests based on an adaptation of Hotelling's T-squared statistic applied to vectors of sample log-cumulants (Mellin statistics) for positive-support reliability data. The package provides the asymptotic chi-squared reference and parametric bootstrap p-values for reliable finite-sample inference, covering the Weibull, Frechet, Gamma, Inverse-Gamma, Log-Normal, and Log-Logistic families. It also provides three diagnostic diagrams (log-cumulant, kurtosis-skewness, and coefficient-of-variation) with bootstrap concentration ellipses, in the spirit of moment-ratio diagrams. Methods are described in Santos, Ospina, Espinheira and Oliveira (2025). Software Depends: R (>= 4.0) Imports: Rcpp, MASS, VGAM, actuar, numDeriv, goftest, ggplot2, gridExtra LinkingTo: Rcpp, RcppArmadillo Suggests: knitr, rmarkdown, testthat (>= 3.0.0) Raydonal Ospina <raydonal@de.ufpe.br> Comprehensive R Archive Network (CRAN) Raydonal Ospina [aut, cre] (ORCID: <https://orcid.org/0000-0002-9884-9090>) GPL-3 2026-06-12 application/tgz https://CRAN.R-project.org/package=logcumulant doi:10.32614/CRAN.package.logcumulant