RAI runs statistics through R. R is free and open source — here is how to get it from the official site in three steps.
Most systems do not come with R. On Windows, nothing else is required after R; XQuartz is optional on macOS — RAI's plot device falls back automatically.
Open cloud.r-project.org — the official site maintained by the R Foundation. No account or payment needed.
Click Download R for macOS, Download R for Windows, or Download R for Linux. You are redirected to a CRAN mirror to fetch the installer.
Open the downloaded file and follow the prompts. That's it — RAI detects R automatically on launch.
R --version. If it prints a version number, R is ready.