Fast and Unified Synthetic Control Methods // A unified 'Formula' interface to the Synthetic Control Method (SCM) and related panel-data causal inference estimators: Synthetic Difference- in-Differences (SDID), Generalized Synthetic Control (GSC), Matrix Completion (MC), Time-Aware Synthetic Control (TASC), and Synthetic Interventions (SI), together with an experimental-design variant. Computational bottlenecks (quadratic programming, singular value decomposition, and Kalman filtering) are implemented in 'C++' via 'RcppArmadillo'. Methods are described in Abadie, Diamond and Hainmueller (2010) doi:10.1198/jasa.2009.ap08746, Arkhangelsky, Athey, Hirshberg, Imbens and Wager (2021) doi:10.1257/aer.20190159, Xu (2017) doi:10.1017/pan.2016.2, Athey, Bayati, Doudchenko, Imbens and Khosravi (2021) doi:10.1080/01621459.2021.1891924, and Agarwal, Shah and Shen (2025) doi:10.1287/opre.2025.1590.