Error: No Rstan Package when using cmdstanr for brms

Interfaces
1

I keep getting this error “Error in utils::packageVersion(“rstan”) : there is no package called ‘rstan’“ but I have installed brms, cmdstanr, and run cmdstanr::install_cmdstan(). I’ve also made sure to set the cmdstanr::set_cmdstan_path. My model refers to cmdstanr for the backend, but it looks like its still trying to pull up rstan.

library(brms)
library(cmdstanr)
brms::brm(var1 ~ var2, 
          data = df, 
          family = hurdle_gamma(), 
          backend = "cmdstanr")

Operating System: Windows
Interface Version: R 4.4.0

How do I get it to stop trying to find the rstan package version so it will run the brms model through cmdstanr?

1 Like
2

brms imports rstan, so rstan needs to be installed even if you use the cmdstanr backend. If you re-install brms, it should prompt you to also install rstan if indeed you don’t have a working installation. Alternatively, you can just install rstan directly.

3

This happens because some versions of brms still check for rstan when loading, even if you’re using cmdstanr as backend. The fix is simple: install a lightweight rstan just to satisfy the dependency check, even if you won’t use it, with install.packages(“rstan”). After that, keep calling your models with backend = “cmdstanr”. If you don’t want to install rstan, you can instead update brms to the latest CRAN or development version (remotes::install_github(“paul-buerkner/brms”)), which removes this requirement. 👊

4

Thanks for the reply. Trying to update to the new development version is still requiring rstan. Unfortunately, I was having issues installing rstan due to server restrictions on downloading Rtools (which resulted in errors about compiling). I will see if I can get new permissions to get Rtools and then rstan.