Tree-Spatial Scan Statistic for Cluster Detection R package treeSS version 0.2.6 Implements the tree-spatial scan statistic for detecting clusters that combine both spatial and hierarchical structures, as proposed by Cancado et al. (2025) <doi:10.1007/s10651-025-00670-w>. The method extends Kulldorff (1997) <doi:10.1080/03610929708831995> circular spatial scan statistic and the tree-based scan statistic of Kulldorff et al. (2003) <doi:10.1111/1541-0420.00039> by searching for anomalies in both geographic regions and branches of hierarchical trees simultaneously. The package also provides standalone implementations of Kulldorff's circular spatial scan statistic and the tree-based scan statistic. Statistical significance is assessed via Monte Carlo simulation under a Poisson or binomial model, with optional 'OpenMP' parallelization. Software Depends: R (>= 3.5.0) Imports: Rcpp (>= 1.0.0), stats LinkingTo: Rcpp Suggests: testthat (>= 3.0.0), knitr, rmarkdown, sf Allan Quadros <allanvcq@gmail.com> Comprehensive R Archive Network (CRAN) Allan Quadros [aut, cre] (ORCID: <https://orcid.org/0000-0003-3250-5380>), Andre L. F. Cançado [aut] (ORCID: <https://orcid.org/0000-0002-7019-8521>) GPL (>= 3) 2026-07-28 application/tgz https://CRAN.R-project.org/package=treeSS doi:10.32614/CRAN.package.treeSS