R-Package 'MIRDD': Diagnostic Tool by Multiple Imputation for Regression Discontinuity Designs. This package estimates average treatment effects at the cutoff based on regression discontinuity designs (RDD) and multiple imputation regression discontinuity designs (MIRDD). It provides diagnostic tools for RDD by comparing results with those from MIRDD, as proposed in Takahashi (2023) https://doi.org/10.1080/03610918.2021.1960374. Also see the package's website on CRAN at https://CRAN.R-project.org/package=MIRDD. A further detail can be found in Takahashi (2026) https://doi.org/10.1016/j.softx.2026.102707.