{
  pkgs ? import (fetchTarball https://github.com/NixOS/nixpkgs-channels/archive/b58ada326aa612ea1e2fb9a53d550999e94f1985.tar.gz) {}
}:

let
  r_pkgs = with pkgs.rPackages; [
    # rmarkdown-related packages.
    knitr
    rmarkdown
    tidyverse
    viridis
    # Rstudio-related packages.
    # servr
  ];
in
pkgs.mkShell {
  buildInputs = [
    pkgs.pandoc
    (pkgs.rWrapper.override {
      packages = r_pkgs;
    })

    # Uncomment to add RStudio in your environment.
    # (pkgs.rstudioWrapper.override {
    #  packages = r_pkgs;
    # })
  ];
}