Regional Consistency Probability for Single-Arm Multi-Regional Clinical Trials R package SingleArmMRCT version 0.1.1 Provides functions to calculate and visualise the Regional Consistency Probability (RCP) for single-arm multi-regional clinical trials (MRCTs) using the Effect Retention Approach (ERA). Six endpoint types are supported: continuous, binary, count (negative binomial), time-to-event via hazard ratio, milestone survival, and restricted mean survival time (RMST). For each endpoint, both a closed-form (or semi-analytical) solution and a Monte Carlo simulation approach are implemented. Two consistency evaluation methods are available: Method 1 (effect retention in Region 1 relative to the overall population) and Method 2 (simultaneous positive effect across all regions). Plotting functions generate faceted visualisations of RCP as a function of the regional allocation proportion, overlaying formula and simulation results for direct comparison. The methodology follows the Japanese MHLW guidelines for MRCTs. Abbreviations used: RCP (Regional Consistency Probability), MRCT (Multi-Regional Clinical Trial), RMST (Restricted Mean Survival Time), MHLW (Ministry of Health, Labour and Welfare). Software Depends: R (>= 4.1.0) Imports: stats, ggplot2 (>= 3.4.0) Suggests: testthat (>= 3.0.0), knitr, rmarkdown Gosuke Homma <my.name.is.gosuke@gmail.com> Comprehensive R Archive Network (CRAN) Gosuke Homma [aut, cre] MIT + file LICENSE (https://CRAN.R-project.org/package=SingleArmMRCT/LICENSE) 2026-04-01 application/tgz https://CRAN.R-project.org/package=SingleArmMRCT doi:10.32614/CRAN.package.SingleArmMRCT en-GB