If you are going to use R 3.6.x, then you need to install rstan from source via
install.packages("rstan", type = "source")
However, upgrading to R 4.0 is better because the binaries work.
If you are going to use R 3.6.x, then you need to install rstan from source via
install.packages("rstan", type = "source")
However, upgrading to R 4.0 is better because the binaries work.